==============================================================================
Claude Code session : 1b654052-359b-4c76-a397-09f16e1a835d
Project directory   : /home/agent/TE_ting_circuitpython
Started             : 2026-07-28 13:24:12
Ended               : 2026-07-28 13:35:06
User prompts        : 3
Claude Code version : 2.1.220
==============================================================================
[2026-07-28 13:24:12] user:
    <command-name>/effort</command-name>
                <command-message>effort</command-message>
                <command-args></command-args>

[2026-07-28 13:24:12] user:
    <local-command-stdout>Set effort level to medium (saved as your default for new sessions): Balanced approach with standard implementation and testing</local-command-stdout>

[2026-07-28 13:26:11] user:
    The TE EP-2350 running CircuitPython is connected. I have learned that it has a poteniometer on the handle that can measure how far pressed the handle is. Currently we've only mapped two buttons for the CircuitPython board def. Can you write a test to discover the pin that the pot is on. I can press and release the handle as needed when the time comes. It won't be GP2 because that is the power hold pin.

[2026-07-28 13:26:13] agent:
    I'll start by looking at the current board definition and how the pins are mapped.

[2026-07-28 13:26:14] tool use: Bash
    command: ls /home/agent/TE_ting_circuitpython
    description: List project directory

[2026-07-28 13:26:14] tool result: Bash
    Adafruit_CircuitPython_LIS331
    Adafruit_CircuitPython_LIS3DH
    Adafruit_CircuitPython_NAU88L21
    Adafruit_CircuitPython_Register
    Adafruit_CircuitPython_TLV320
    audio_codec_bringup_session3.md
    boot.py
    circuitpython
    circuitpython_codec_findings.md
    code_ep2350_demo.py
    code_passthrough_amp.py
    code_passthrough.py
    code.py
    code_usb_mic_passthru.py
    DS_NAU88L21_DataSheet_EN_Rev2.8.pdf
    ep2350_codec.py
    ep-2350-info.md
    i2s_external_clock_plan.md
    mic_findings.md
    nau88l21_driver_plan.md
    Nuvoton-ASoC
    __pycache__
    register_address_width_plan.md
    RP-008373-DS-2-rp2350-datasheet.pdf
    scratchpad
    scripts
    test_audio.wav
    test_recording.wav

[2026-07-28 13:26:15] tool use: Bash
    command: cat /home/agent/.claude/projects/-home-agent-TE-ting-circuitpython/memory/ep2350-repl-workflow.md /home/agent/.claude/projects/-home-agent-TE-ting-circuitpython/memory/ep2350-dangerous-pins.md
    description: Read workflow memories

[2026-07-28 13:26:15] tool result: Bash
    ---
    name: ep2350-repl-workflow
    description: "How to drive the EP-2350 CircuitPython board over the raw REPL, including the gotcha that state is lost between connections"
    metadata: 
      node_type: memory
      type: project
      originSessionId: 7bfa2c3d-a166-4115-bfc2-fc7a59c14a8f
      modified: 2026-07-19T23:14:44.971Z
    ---
    
    The EP-2350 runs CircuitPython on `/dev/ttyACM0`, mounting as
    `/media/timc/CIRCUITPY/`. Use `~/agent_venv/` (has pyserial, numpy) for host-side
    code. Drive the board via the **raw REPL** (ctrl-C ctrl-C, ctrl-A, code, ctrl-D).
    
    **Why:** `ampy`/`circup` are installed but the raw REPL is the only way to run
    ad-hoc test code and read results back without touching the filesystem.
    
    **How to apply:**
    - **Board state does NOT survive closing the serial port.** Objects created in
      one exec are gone on the next connection. Anything that must stay alive while
      the host does something (e.g. `arecord`) has to run in the *same* exec — write
      the setup, then `time.sleep(n)`, and do the host-side work concurrently.
    - An exec that raises leaves objects un-deinit'd, so the next run fails with
      `ValueError: GPnn in use`. Wrap teardown in a `cleanup()` helper.
    - CIRCUITPY is read-only to the board while USB MSC is mounted; use `io.BytesIO`
      as a sink and `binascii.b2a_base64` to ship data back to the host.
    - RAM is ~400 KB free; an `array.array("h")` of 44100 already fails to allocate.
    
    See [[audio-test-rig]] for verifying audio output.
    ---
    name: ep2350-dangerous-pins
    description: GP2 on the EP-2350 powers the unit off if driven low; GP25/26/27 are not really floating
    metadata: 
      node_type: memory
      type: project
      originSessionId: 585846fd-0977-4015-ae39-5cd0bfdf85d5
      modified: 2026-07-23T18:08:37.696Z
    ---
    
    **Never drive GP2.** It is `POWER_HOLD` — driving it low powers the EP-2350 off
    instantly and the user has to physically power it back on. Never sweep a range
    of GPIOs configuring them as outputs; pick pins deliberately from
    `boards/teenage_engineering_ep2350/pins.c`.
    
    **Also never call `microcontroller.reset()`** over the REPL — verified 2026-07-23
    it drops POWER_HOLD and powers the board OFF (needs a physical power-on), it does
    NOT just reboot. To re-run code use Ctrl-D (soft reboot) or save a file over USB.
    Note: repeated soft reboots can wedge the NAU88L21 codec's I2C/FLL bring-up, so
    `import code_ep2350_demo` throws `OSError [Errno 5]` at code.py line 4 — retry
    Ctrl-D a few times and it comes up; it is not a code bug. See
    [[ep2350-repl-workflow]].
    
    **Why:** on 2026-07-20 a loop that tried every `board.GPn` as a PIO set-pin
    killed the board mid-session.
    
    **How to apply:** the genuinely safe scratch pins are **GP7, GP13, GP22, GP23** —
    they float and respond to the internal pulls. GP25/GP26/GP27 are labelled
    "unconnected" in `pins.c` but all three read high against an armed internal
    pull-down, so they are useless as pull-sensing test pins. Also in use: GP0/4/5/6
    and GP16/17/18/24 (LEDs), GP1/3/21 (buttons), GP19/20 (handle), GP8-GP12 (I2S),
    GP14/15 (I2C), GP28/29 (rail sense, volume pot).
    
    See [[ep2350-repl-workflow]] and [[ep2350-firmware-build]].

[2026-07-28 13:26:18] thinking: [not recorded in transcript]

[2026-07-28 13:26:20] tool use: Bash
    command: cd /home/agent/TE_ting_circuitpython/circuitpython/ports/raspberrypi/boards/teenage_engineering_ep2350 && ls && cat pins.c && cat mpconfigboard.h 2>/dev/null | head -40
    description: Read board pin definitions

[2026-07-28 13:26:20] tool result: Bash
    board.c
    mpconfigboard.h
    mpconfigboard.mk
    pico-sdk-configboard.h
    pins.c
    // This file is part of the CircuitPython project: https://circuitpython.org
    //
    // SPDX-FileCopyrightText: Copyright (c) 2026 Tim Cocks
    //
    // SPDX-License-Identifier: MIT
    
    #include "shared-bindings/board/__init__.h"
    
    static const mp_rom_map_elem_t board_module_globals_table[] = {
        CIRCUITPYTHON_BOARD_DICT_STANDARD_ITEMS
    
        // LEDs, one dedicated GPIO each, active high.
        // Two columns of four, numbered top (nearest the handle) to bottom.
        // Note: GP0 and GP16 share a PWM slice/channel, so the their LEDs
        // cannot be PWM-dimmed independently.
        { MP_ROM_QSTR(MP_QSTR_GP0), MP_ROM_PTR(&pin_GPIO0) },
        { MP_ROM_QSTR(MP_QSTR_LED_WHITE1), MP_ROM_PTR(&pin_GPIO0) },
        { MP_ROM_QSTR(MP_QSTR_LED), MP_ROM_PTR(&pin_GPIO0) },
    
        { MP_ROM_QSTR(MP_QSTR_GP6), MP_ROM_PTR(&pin_GPIO6) },
        { MP_ROM_QSTR(MP_QSTR_LED_WHITE2), MP_ROM_PTR(&pin_GPIO6) },
    
        { MP_ROM_QSTR(MP_QSTR_GP4), MP_ROM_PTR(&pin_GPIO4) },
        { MP_ROM_QSTR(MP_QSTR_LED_WHITE3), MP_ROM_PTR(&pin_GPIO4) },
    
        { MP_ROM_QSTR(MP_QSTR_GP5), MP_ROM_PTR(&pin_GPIO5) },
        { MP_ROM_QSTR(MP_QSTR_LED_WHITE4), MP_ROM_PTR(&pin_GPIO5) },
    
        { MP_ROM_QSTR(MP_QSTR_GP16), MP_ROM_PTR(&pin_GPIO16) },
        { MP_ROM_QSTR(MP_QSTR_LED_RED1), MP_ROM_PTR(&pin_GPIO16) },
    
        { MP_ROM_QSTR(MP_QSTR_GP24), MP_ROM_PTR(&pin_GPIO24) },
        { MP_ROM_QSTR(MP_QSTR_LED_RED2), MP_ROM_PTR(&pin_GPIO24) },
    
        { MP_ROM_QSTR(MP_QSTR_GP18), MP_ROM_PTR(&pin_GPIO18) },
        { MP_ROM_QSTR(MP_QSTR_LED_RED3), MP_ROM_PTR(&pin_GPIO18) },
    
        { MP_ROM_QSTR(MP_QSTR_GP17), MP_ROM_PTR(&pin_GPIO17) },
        { MP_ROM_QSTR(MP_QSTR_LED_RED4), MP_ROM_PTR(&pin_GPIO17) },
    
        // Side buttons. Switches to ground, no external pull-ups: use Pull.UP,
        // pressed reads False.
        { MP_ROM_QSTR(MP_QSTR_GP21), MP_ROM_PTR(&pin_GPIO21) },
        { MP_ROM_QSTR(MP_QSTR_BUTTON_TOP), MP_ROM_PTR(&pin_GPIO21) },
    
        { MP_ROM_QSTR(MP_QSTR_GP3), MP_ROM_PTR(&pin_GPIO3) },
        { MP_ROM_QSTR(MP_QSTR_BUTTON_MIDDLE), MP_ROM_PTR(&pin_GPIO3) },
    
        { MP_ROM_QSTR(MP_QSTR_GP1), MP_ROM_PTR(&pin_GPIO1) },
        { MP_ROM_QSTR(MP_QSTR_BUTTON_BOTTOM), MP_ROM_PTR(&pin_GPIO1) },
    
        // Handle: a two-stage switch. HANDLE_IN reads False when the handle is
        // fully seated; HANDLE_OUT reads True as soon as the handle is moved.
        { MP_ROM_QSTR(MP_QSTR_GP19), MP_ROM_PTR(&pin_GPIO19) },
        { MP_ROM_QSTR(MP_QSTR_HANDLE_IN), MP_ROM_PTR(&pin_GPIO19) },
    
        { MP_ROM_QSTR(MP_QSTR_GP20), MP_ROM_PTR(&pin_GPIO20) },
        { MP_ROM_QSTR(MP_QSTR_HANDLE_OUT), MP_ROM_PTR(&pin_GPIO20) },
    
        // Power hold latch. Held high by the board so the unit stays powered once
        // the handle is released. Driving it low powers the unit off immediately.
        { MP_ROM_QSTR(MP_QSTR_GP2), MP_ROM_PTR(&pin_GPIO2) },
        { MP_ROM_QSTR(MP_QSTR_POWER_HOLD), MP_ROM_PTR(&pin_GPIO2) },
    
        // I2C1: NAU88L21 codec at 0x1b, accelerometer at 0x18. External pull-ups.
        { MP_ROM_QSTR(MP_QSTR_GP14), MP_ROM_PTR(&pin_GPIO14) },
        { MP_ROM_QSTR(MP_QSTR_SDA), MP_ROM_PTR(&pin_GPIO14) },
    
        { MP_ROM_QSTR(MP_QSTR_GP15), MP_ROM_PTR(&pin_GPIO15) },
        { MP_ROM_QSTR(MP_QSTR_SCL), MP_ROM_PTR(&pin_GPIO15) },
    
        // I2S to the codec. The codec is the I2S clock source (it drives BCLK and
        // LRCLK); the MCU only supplies MCLK.
        { MP_ROM_QSTR(MP_QSTR_GP8), MP_ROM_PTR(&pin_GPIO8) },
        { MP_ROM_QSTR(MP_QSTR_I2S_DIN), MP_ROM_PTR(&pin_GPIO8) },
    
        { MP_ROM_QSTR(MP_QSTR_GP9), MP_ROM_PTR(&pin_GPIO9) },
        { MP_ROM_QSTR(MP_QSTR_I2S_DOUT), MP_ROM_PTR(&pin_GPIO9) },
    
        { MP_ROM_QSTR(MP_QSTR_GP10), MP_ROM_PTR(&pin_GPIO10) },
        { MP_ROM_QSTR(MP_QSTR_I2S_WS), MP_ROM_PTR(&pin_GPIO10) },
    
        { MP_ROM_QSTR(MP_QSTR_GP11), MP_ROM_PTR(&pin_GPIO11) },
        { MP_ROM_QSTR(MP_QSTR_I2S_BIT_CLOCK), MP_ROM_PTR(&pin_GPIO11) },
    
        { MP_ROM_QSTR(MP_QSTR_GP12), MP_ROM_PTR(&pin_GPIO12) },
        { MP_ROM_QSTR(MP_QSTR_I2S_MCLK), MP_ROM_PTR(&pin_GPIO12) },
    
        // Unidentified / unconnected.
        { MP_ROM_QSTR(MP_QSTR_GP7), MP_ROM_PTR(&pin_GPIO7) },
        { MP_ROM_QSTR(MP_QSTR_GP13), MP_ROM_PTR(&pin_GPIO13) },
        { MP_ROM_QSTR(MP_QSTR_GP22), MP_ROM_PTR(&pin_GPIO22) },
        { MP_ROM_QSTR(MP_QSTR_GP23), MP_ROM_PTR(&pin_GPIO23) },
        { MP_ROM_QSTR(MP_QSTR_GP25), MP_ROM_PTR(&pin_GPIO25) },
    
        // Analog. GP26/GP27 are unconnected.
        { MP_ROM_QSTR(MP_QSTR_GP26), MP_ROM_PTR(&pin_GPIO26) },
        { MP_ROM_QSTR(MP_QSTR_A0), MP_ROM_PTR(&pin_GPIO26) },
    
        { MP_ROM_QSTR(MP_QSTR_GP27), MP_ROM_PTR(&pin_GPIO27) },
        { MP_ROM_QSTR(MP_QSTR_A1), MP_ROM_PTR(&pin_GPIO27) },
    
        // Rail sense through a resistive divider (VSYS/VBAT / 2).
        { MP_ROM_QSTR(MP_QSTR_GP28), MP_ROM_PTR(&pin_GPIO28) },
        { MP_ROM_QSTR(MP_QSTR_A2), MP_ROM_PTR(&pin_GPIO28) },
        { MP_ROM_QSTR(MP_QSTR_VOLTAGE_MONITOR), MP_ROM_PTR(&pin_GPIO28) },
    
        // Volume potentiometer wiper, full scale 0 - 3.3V.
        { MP_ROM_QSTR(MP_QSTR_GP29), MP_ROM_PTR(&pin_GPIO29) },
        { MP_ROM_QSTR(MP_QSTR_A3), MP_ROM_PTR(&pin_GPIO29) },
        { MP_ROM_QSTR(MP_QSTR_VOLUME), MP_ROM_PTR(&pin_GPIO29) },
    
        { MP_ROM_QSTR(MP_QSTR_I2C), MP_ROM_PTR(&board_i2c_obj) },
    };
    MP_DEFINE_CONST_DICT(board_module_globals, board_module_globals_table);
    // This file is part of the CircuitPython project: https://circuitpython.org
    //
    // SPDX-FileCopyrightText: Copyright (c) 2026 Tim Cocks
    //
    // SPDX-License-Identifier: MIT
    
    #define MICROPY_HW_BOARD_NAME "Teenage Engineering ting fx EP-2350"
    #define MICROPY_HW_MCU_NAME "rp2350a"
    
    // Top white LED. Also available as board.LED_WHITE1.
    #define MICROPY_HW_LED_STATUS (&pin_GPIO0)
    
    // GPIO2 is the power hold latch: high keeps the unit powered, low powers it
    // off immediately. It is asserted in board_reset_pin_number() so that it
    // survives every pin reset.
    #define MICROPY_HW_POWER_HOLD_PIN_NUMBER (2)
    
    // Codec (0x1b) and accelerometer (0x18) share I2C1. External pull-ups.
    #define CIRCUITPY_BOARD_I2C         (1)
    #define CIRCUITPY_BOARD_I2C_PIN     {{.scl = &pin_GPIO15, .sda = &pin_GPIO14}}

[2026-07-28 13:26:21] tool use: Bash
    command: cat /home/agent/TE_ting_circuitpython/ep-2350-info.md
    description: Read board info notes

[2026-07-28 13:26:21] tool result: Bash
    # EP-2350 "Ting" — hardware reference
    
    Consolidated hardware facts for the Teenage Engineering EP-2350. MCU is an
    **RP2350A** (GPIO0–GPIO29 only). Audio codec is a **Nuvoton NAU88L21**.
    
    ---
    
    ## 1. Complete GPIO map
    
    | GPIO | Function | Direction / sense |
    |-----:|----------|-------------------|
    | **0** | LED — white 1 (top, nearest handle) | out, active high |
    | **1** | Side button — bottom | in, 0 = pressed (needs internal pull-up) |
    | **2** | **POWER HOLD latch** | out, **high = stay powered, low = power off** |
    | **3** | Side button — middle | in, 0 = pressed (needs internal pull-up) |
    | **4** | LED — white 3 | out, active high |
    | **5** | LED — white 4 (bottom) | out, active high |
    | **6** | LED — white 2 | out, active high |
    | 7 | unidentified | — |
    | **8** | I²S **DIN** — codec ADCOUT → MCU | codec output |
    | **9** | I²S **DOUT** — MCU → codec DACIN | codec input (board pull-up, idles high) |
    | **10** | I²S **FS / LRCLK / WS** | codec output in codec-master mode |
    | **11** | I²S **BCLK** | codec output in codec-master mode |
    | **12** | I²S **MCLK** (codec master clock) | MCU output |
    | 13 | unidentified | — |
    | **14** | **I²C1 SDA** (codec + accelerometer) | external pull-up |
    | **15** | **I²C1 SCL** (codec + accelerometer) | external pull-up |
    | **16** | LED — red 1 (top, nearest handle) | out, active high |
    | **17** | LED — red 4 (bottom) | out, active high |
    | **18** | LED — red 3 | out, active high |
    | **19** | Handle switch — **fully in** (travel end-stop) | in, 0 = pressed |
    | **20** | Handle switch — **at rest** | in, 0 = handle released, 1 = handle held |
    | **21** | Side button — top (nearest handle) | in, 0 = pressed (needs internal pull-up) |
    | 22, 23 | unidentified | — |
    | **24** | LED — red 2 | out, active high |
    | 25 | unidentified (not ADC-capable) | — |
    | 26 (ADC0) | floating / unconnected | — |
    | 27 (ADC1) | floating / unconnected | — |
    | **28 (ADC2)** | analog rail sense (VSYS/VBAT ÷ 2, likely) | real divider, R_th ≈ 4.6 kΩ |
    | **29 (ADC3)** | **Volume knob** (potentiometer wiper) | analog, 0 → 3.29 V |
    
    Unidentified pins: GP7, GP13, GP22, GP23, GP25, plus a `get_vbus` digital
    VBUS-present sense line that has no candidate pin.
    
    ### I²C bus
    
    Hardware **I2C1** on SDA=GP14 / SCL=GP15, external pull-ups. Only two devices:
    
    | Address | Device |
    |---------|--------|
    | `0x18` | accelerometer (shake detection) |
    | `0x1b` | NAU88L21 codec (CSB strap = 0) |
    
    There is **no PMIC / power-management chip** on the bus.
    
    ---
    
    ## 2. Power
    
    **GPIO2 is the power hold latch.** Drive it HIGH to keep the unit powered; drive
    it LOW to power off immediately.
    
    ```python
    from machine import Pin
    hold = Pin(2, Pin.OUT, value=1)   # assert before the handle is released
    # hold.value(0)                   # cut power
    ```
    
    Behaviour:
    
    - **At power-on the latch is OFF.** The handle switch supplies power directly
      while it is held in. Firmware that never asserts GP2 dies the instant the
      handle is released.
    - **It is a true set/reset latch, not a keep-alive.** Once set, it retains even
      with GP2 floating (all output-enables cleared) — no periodic refresh needed.
    - **Driving GP2 LOW resets the latch → instant power-off**, USB drops.
    - Pressing the handle is the only way to power the unit *on*; plugging in USB
      does not power on a powered-off unit.
    - **Pulling USB powers the unit off**, even with the latch set and batteries
      fitted — it does not fall back to battery. The power-path handover appears to
      brown out the RP2350, which releases GP2 and clears the latch.
    - The documented 5-minute power-save / 20-minute auto-off are firmware timers on
      top of this: the stock firmware watches GP19, then drives GP2 low.
    
    **⚠️ Never call `machine.reset()` on this board** — it releases GP2, clearing the
    latch, and the unit powers off completely, requiring a physical power-on.
    
    Rail sensing: **GP28 (ADC2)** is the only genuine analog sense line — a real
    resistive divider (R_th ≈ 4.6 kΩ, consistent with 10k‖10k). VSYS/VBAT ÷ 2 is the
    leading interpretation (its reading moved −7.7 % when batteries were fitted), but
    VBUS ÷ N has not been fully excluded.
    
    ---
    
    ## 3. Audio interface (NAU88L21)
    
    ### 3.1 Topology
    
    | Item | Value |
    |------|-------|
    | Codec | NAU88L21, I²C address **`0x1b`**, ID register `0x58` reads **`0x1b23`** |
    | Register access | **16-bit register address, 16-bit data, big-endian** |
    | MCLK | **GP12**, driven by the MCU (`machine.PWM`) |
    | BCLK | **GP11** = MCLK / 8 |
    | FS / LRCLK | **GP10** = BCLK / 32 = MCLK / 256 |
    | DACIN (MCU → codec) | **GP9** |
    | ADCOUT (codec → MCU) | **GP8** |
    | Microphone | **one analog mic on the codec's LEFT channel** (MICL+/MICL− → FEPGA → ADCL). Right channel carries no signal — the mic path is **mono**. |
    | Headphone | codec HP amp → jack; the analog path **inverts** |
    | Volume knob | not connected to the codec — it is an ADC input on GP29 (§1) |
    
    ### 3.2 Working clock configuration
    
    The reliable topology is **codec = I²S master, MCU = I²S slave** (both TX and
    RX), with the MCU supplying only MCLK on GP12. The codec's own slave-mode I²S
    receiver does not render data reliably; codec-master does.
    
    ```
    machine.freq(144_000_000)
    MCLK  = 12.000 MHz on GP12 (PWM, sysclk ÷ 12)
    BCLK  = MCLK / 8   = 1.5 MHz     (codec output, GP11)
    FS    = BCLK / 32  = 46875 Hz    (codec output, GP10)
    MCLK / fs = 256 exactly; codec DAC clk = SYSCLK/2 with OSR128 → coherent
    ```
    
    `machine.freq(153_600_000)` is also settable and yields exact fs = 48000 if
    wanted. 147.456 MHz and 122.88 MHz are **not** settable.
    
    The MCU must set **GP10 and GP11 to `Pin.IN`** — they are codec outputs in this
    mode and driving them causes bus contention.
    
    Frame/phase facts: FS transitions on **BCLK falling** edges; frame = 32 BCLK
    (16 per channel); the codec latches DACIN on **BCLK rising**, and drives ADCOUT
    on **BCLK rising** — so a PIO receiver must sample ADCOUT on **BCLK falling**
    (mid-bit) to be deterministic.
    
    ### 3.3 Codec registers — I²S
    
    ```
    0x1C  I2S_PCM_CTRL1 = 0x0001    DL_16 | DF_LEFT (left-justified, 16-bit)
    0x1D  I2S_PCM_CTRL2 = 0x301B    I2S_TRI=0 (bit15 — default 1 tri-states all
                                    I²S pins!), LRC_DIV=11 (FS=BCLK/32),
                                    MS0=1 (master), BCLK_DIV=011 (BCLK=MCLK/8)
    0x03  CLK_DIVIDER   = 0x0050    default: SYSCLK from MCLK pin, no FLL needed
    0x01  ENA_CTRL      = 0x00FF    default already has CLK_I2S_EN=1
    ```
    
    Reg 0x1D bit map: `I2S_TRI`=b15, `LRC_DIV`=[13:12], `ADCDAT0_OE`=b4, `MS0`=b3,
    `BCLK_DIV`=[2:0].
    
    ### 3.4 Codec registers — DAC → headphone playback
    
    ```
    0x01  ENA_CTRL   = 0x0CFF   EN_DACL/R (b10/b11) + low clocks incl EN_DAC_CLK
    0x2C  DAC_CTRL1  = 0x0082   default, OSR128
    0x31  MUTE       = 0x0000
    0x32  HSVOL      = 0x0000   0 dB headset volume
    0x34  DAC gain   = 0xCFCF   DGAINL=[7:0], DGAINR=[15:8]; ≈ +0.5 dB
    0x0D              = 0xC000  output pulldowns disabled
    0x4B              = 0x0007  class-G enable + L/R DAC
    0x66  BIAS_ADJ   = 0x0060   VMIDEN + VMID_SEL=125k
    0x6A              = 0x1003
    0x73  RDAC       = 0x772C   DACL/R_EN + DACL/R_CLK_EN
    0x76  BOOST      = 0x3140   HP boost
    0x7F              = 0x003F  HP output drivers
    0x80              = 0x0020  charge pump enable
    ```
    
    **⚠️ R66 bits [9:8] are BIAS_TESTDAC** (`0x100`=L, `0x200`=R). Setting them
    switches both DACs to a test input tied to GND — guaranteed silence. Keep them
    clear (`R66 = 0x0060`).
    
    ### 3.5 Codec registers — microphone / ADC capture
    
    Applied on top of the master-I²S setup, in this order:
    
    ```
    0x66 = 0x0060       VMIDEN + VMID tie-off (bias first)
    0x76 = 0x1000       GLOBAL_BIAS_EN
    0x71 = 0x0011       MIC-detect powered down (default)
    0x74 = 0x0106       MICBIAS POWERUP + default voltage
    0x77 = 0x0000       FEPGA: MICP/MICN connected
    0x7E = gg<<8 | gg   FEPGA gain: 0x00 = −1 dB … 0x25 = 36 dB
    0x7F = 0xC000       PUP_PGA_L | PUP_PGA_R
    0x72 = 0x0070       ADC analog power: PDNOTL | PDNOTR
    0x2B = 0x0002       ADC rate
    0x30 = 0x0000
    0x35 = 0xCFCF       ADC digital gains (0 dB)
    0x01 = 0x03FF       defaults + EN_ADCL (b8) | EN_ADCR (b9)
    ```
    
    Allow **~400 ms** after the analog power-up before capturing — 60 ms yields
    samples but the bias is still ramping and the capture is a DC drift with almost
    no AC content. The ADC's DC offset continues decaying for the first 1–2 s; high-
    pass (~120–150 Hz) or discard the first second if you need a stable baseline.
    
    `0x35` ADCR_CH_VOL has no effect on the right-slot word (ADCL_CH_VOL works
    bit-exactly). Irrelevant in practice — the right slot carries no audio.
    
    The codec's internal `R55 D2A_LOOP` (ADC→DAC) does not appear to work; route
    audio digitally through the MCU instead.
    
    ### 3.6 I²S word layout
    
    - **RX (from ADCOUT):** syncing on **FS falling** starts in the right-channel
      slot, so each 32-bit word is `[right << 16 | left]` — **the mic sample is the
      LOW half**. Syncing on FS rising lands one bit early.
    - **TX (to DACIN):** slot order is `[left, right]`.
    
    Consequence: a byte-for-byte RX→TX passthrough puts the mic in the *right* slot
    and silence in the left. For mono duplication, do it in the PIO TX program:
    
    ```
    pull(); out(null,16); mov(x,osr); <16 bits>; mov(osr,x); <16 bits>
    ```
    
    **Autopull must be OFF** for this — with `autopull=True, pull_thresh=32` the
    refill fires immediately before `mov(osr, x)` and clobbers the fresh word,
    eating every other sample. Use an explicit blocking `pull()` per frame.
    
    ### 3.7 Bring-up requirements (all mandatory)
    
    1. **Abort every DMA channel before a PIO+DMA bring-up.** `machine.soft_reset()`
       does *not* stop running `rp2.DMA()` channels; orphans keep writing the PIO TX
       FIFO and the next bring-up either starves (total silence) or renders garbage.
       RP2350 `CHAN_ABORT` = `0x50000000 + 0x464`; write a channel bitmap (`0xFFFF`),
       poll until it self-clears, and also clear each channel's non-triggering CTRL
       alias (`chan_base + 0x10`).
    2. **Free the PIO before re-running.** `soft_reset` leaves SMs and instruction
       memory claimed → `ENOMEM` at `StateMachine(...)`. Clear `PIO0/1 CTRL`
       (SM_ENABLE=0) and call `rp2.PIO(n).remove_program()`.
    3. **Arm the TX DMA *before* `sm.active(1)`.** Otherwise the slave TX syncs to an
       FS edge, stalls at `out` on an empty FIFO, and resumes mid-frame with word
       alignment lost → scrambled output.
    4. **Put RX and TX on separate PIO blocks** (e.g. RX on PIO1, TX on PIO0) — they
       share 32-slot instruction memory within a block.
    5. Sample ADCOUT on **BCLK falling** (§3.2).
    
    With these in place the slave-TX word phase is **deterministic** (measured
    offset 0 on 10/10 bring-ups) — no retry loop is needed.
    
    ### 3.8 Validated audio routes
    
    | Route | Status |
    |-------|--------|
    | Tone generation → DAC → headphone jack | Working, deterministic, SNR 260–745 |
    | Mic → ADC → RAM (≤ ~1 s, 187 KB buffer) | Working |
    | Mic → ADC → DMA ring → host over REPL (unbounded length) | Working, 0 overruns at 94 KB/s |
    | Mic → RAM → DAC → headphone (record then replay) | Working, verified by matched filter (r = 0.988) |
    | **Live mic → headphone passthrough, zero CPU in the data path** | Working |
    
    The passthrough works because both PIO SMs are I²S slaves to the same codec
    BCLK/FS, so each moves exactly one word per frame. Two free-running DMA channels
    wrap inside the *same* aligned buffer — RX wrapping its **write** address
    (`ring_sel=1`), TX wrapping its **read** address (`ring_sel=0`) — so the gap
    between pointers is fixed at startup and never drifts. Latency = that gap
    (64 words ≈ 1.4 ms by default); keep it above 8 words, since the TX FIFO
    pre-buffers 8.
    
    Level control without CPU involvement: `0x7E` (analog FEPGA gain) and `0x34`
    (DAC digital gain). Output level at the jack is low as configured — raise DAC or
    HP gain for a listening demo.
    
    Practical limits: ~1 s is the maximum in-RAM capture (2 s raises `MemoryError`);
    extracting the low half of each word must be `@micropython.viper` to keep up
    with 46875 words/s. Measured device fs runs +0.13–0.2 % vs the nominal 46875 Hz.
    
    ---
    
    ## 4. LEDs
    
    Eight LEDs, **eight dedicated GPIOs, one per LED, active HIGH**. No matrix,
    charlieplexing, shift register, or enable line.
    
    | Position (top → bottom) | Red column | White column |
    |---|---:|---:|
    | 1 (nearest handle) | **GP16** | **GP0** |
    | 2 | **GP24** | **GP6** |
    | 3 | **GP18** | **GP4** |
    | 4 | **GP17** | **GP5** |
    
    ```python
    RED   = [16, 24, 18, 17]     # top -> bottom
    WHITE = [0,  6,  4,  5]      # top -> bottom
    ```
    
    - Full brightness is just a digital `1`. Each LED has its own series resistor, so
      raising pad drive strength (4 mA → 12 mA) makes no visible difference.
    - Dimming is plain PWM (`freq(1000)`, `duty_u16()`) — clean and monotonic.
      duty ≈ 1200/65535 is a comfortable dim-indicator level.
    - `Pin.IN` with no pull = fully off. `Pin.IN, Pin.PULL_UP` gives a free dim
      standby glow (the internal pull-up sources ~40 µA through the LED).
    - **⚠️ GP0 and GP16 share a PWM slice/channel.** The top red and top white LEDs
      cannot be PWM-dimmed independently — the second `duty_u16()` silently
      overrides the first. Use PWM on one and plain on/off on the other. The
      mirroring only occurs when a pin is actually muxed to the PWM function.
    
    ---
    
    ## 5. Controls
    
    ### Buttons
    
    All five are simple switches to ground with **no external pull-ups** — every one
    needs `Pin(n, Pin.IN, Pin.PULL_UP)`.
    
    | Button | GPIO | Sense |
    |--------|-----:|-------|
    | Side button — top (nearest handle) | **GP21** | 0 = pressed |
    | Side button — middle | **GP3** | 0 = pressed |
    | Side button — bottom | **GP1** | 0 = pressed |
    | Handle fully in (travel end-stop) | **GP19** | 0 = pressed |
    | Handle at rest / not held | **GP20** | 0 = released, 1 = held |
    
    **The handle is a two-stage switch.** GP19 and GP20 are separate switches on the
    same mechanism and change in sequence, with a dead band mid-travel where both
    read 1:
    
    - `GP20 == 1` is the earliest "user is touching the handle" signal — it fires
      ~300 ms before GP19 confirms full insertion.
    - `GP19 == 0` means fully seated; this is what gates the power-on path.
    - Neither pin alone tells you the handle position — use the pair.
    
    Baseline `GPIO_IN` with the handle in and nothing pressed: `0x3ff7ffff`.
    
    ### Volume knob
    
    A plain potentiometer across the 3V3 rail with its wiper on **GP29 = ADC3**. It
    is wired to the RP2350, **not** to the codec.
    
    ```python
    from machine import ADC
    vol = ADC(3)                 # GP29
    level = vol.read_u16()       # 0..65535, full scale usable
    ```
    
    - Not a rotary encoder, and there is **no integral push-switch** — no digital pin
      moves during any knob action.
    - Range: 68 counts (0.003 V) at minimum → 65340 counts (3.290 V) at maximum. It
      bottoms out at both rails, so full scale is usable without calibration.
    - Static noise: ±3 counts on a 16-sample average.
    - Taper is not established (linear vs mild audio taper is within measurement
      error) — treat the raw value as a control input and apply taper in software.
    
    ---
    
    ## 6. Firmware & bootloader
    
    - The board ships with a custom TE MicroPython build (`_machine = 'EP-2350 1.0.8'`,
      MicroPython v1.26.0-preview). It has **no `machine` module**; available modules
      include `rp2, _rp2, uctypes, micropython, teenage, ui, spl, fx, test, vfs, os`.
      Register access there must go through `uctypes.struct`. Audio/codec bring-up
      lives in the compiled C modules `ui`/`spl`/`fx`, not in Python.
    - Everything in this document was validated under **stock MicroPython for the
      Pico 2 (`RPI_PICO2`, ARM build)**, which the board runs fine.
    - **Update mode:** remove the lower lid, connect USB-C, hold the handle, then
      double-click the small button above the USB-C port. A drive named **`TING BOOT`**
      appears (USB `2367:0620`, `INFO_UF2.TXT` → `UF2 Bootloader v1.0 / Model:
      EP-2350`).
    - This is **TE's own flash-resident bootloader, not the RP2350 ROM BOOTSEL**, so
      **`picotool` cannot see it**. Flash by drag-and-drop of a UF2 onto the drive.
      TE UF2s are standard RP2350 UF2s (base `0x10000000`, family `0xe48bff59` =
      RP2350 ARM-S), the same format as the stock MicroPython image.
    - The real ROM BOOTSEL (drive `rp2350`, USB `2e8a:000f`) is reachable — from
      running MicroPython, `machine.bootloader()` enters it, and `picotool` works
      there. **Note this also cuts power to the latch.**
    - Restore stock TE firmware by dragging `ep-2350_firmware_1_0_8.uf2` onto either
      drive.
    
    ### QSPI flash — size and layout
    
    **Winbond W25Q16JV — 2 MB (16 Mbit) on CS0. Nothing on CS1.** JEDEC RDID
    (`0x9F`) returns `EF 40 15`: `0xEF` Winbond, device `0x4015` = W25Q16 family in
    the standard-SPI (`0x40`) variant, i.e. W25Q16JV-IQ/JQ; capacity byte `0x15` =
    2²¹ = 2 MB, which agrees with the aliasing measurement below.
    
    | flash range | size | contents |
    |---|---|---|
    | `0x000000`–`0x0E47FF` | 929 KB | firmware image; matches `ep-2350_firmware_1_0_8.uf2` byte ranges exactly, including the `/rom` romfs at `0x0E0000` (18,339 B) |
    | `0x0E4800`–`0x0FFFFF` | 110 KB | erased `0xFF`, unused |
    | `0x100000`–`0x1FFFFF` | 1 MB | FAT12 volume `NO NAME` = `/fat`, the user drive |
    
    `/fat`: 4096-byte sectors, 1 reserved, 1 FAT sector, 512 root entries, **250 data
    clusters × 4 KB = 1000 KB**. `rp2.Flash()` exposes exactly this region
    (`ioctl(4)` = 256 blocks, `ioctl(5)` = 4096). `os.statvfs('/fat')` on a factory
    device with no samples loaded reports all 250 clusters free.
    
    **How the size was measured** (all reads passive via `uctypes`, safe on live
    firmware): XIP address aliasing. Content at `+1 MB` differs, but `+2 MB`, and the
    `0x400000`/`0x800000`/`0xC00000` flash offsets reached through the other ATRANS
    windows, are byte-identical to offset 0 — 48 scattered 64-byte samples over a
    4 MB span, 24 of them non-uniform, zero mismatches. So the chip ignores A21 and
    up. `0x11000000` (CS1) reads back as `0xCC` filler.
    
    Two traps that make the flash look bigger than it is:
    
    - **`QMI_ATRANS0` is not at its reset value.** Observed
      `ATRANS0 = 0x04000C00` → base `0xC00000`, size 4 MB; `ATRANS1..4` hold the
      default `0x000000/0x400000/0x800000/0xC00000` bases and `ATRANS5..7` are zero.
      So `0x10000000` nominally maps to flash 12 MB — which wraps to 0 on a 2 MB
      part. The windows are the default sequence rotated by one slot.
    - **OTP says nothing.** `FLASH_DEVINFO` (row `0x054`, guarded read at
      `0x40130000 + row*2`) is `0x0000`, and `BOOT_FLAGS0` (row `0x048`) is `0x0000`,
      so `FLASH_DEVINFO_ENABLE` is clear and the bootrom is running on its **default
      assumption of 16 MB CS0** — not a measured value. That default is the likely
      reason for the ATRANS rotation.
    
    OTP read strides (both verified against the CHIPID rows): guarded/ECC-corrected
    `0x40130000 + row*2` (16 bits per row), raw `0x40134000 + row*4` (24 bits, data
    in the low 16). Config rows are triple-redundant, e.g. `BOOT_FLAGS1` at
    `0x04B`/`0x04C`/`0x04D` = `0x0020`.
    
    #### Reading the JEDEC ID (done under stock MicroPython)
    
    Not passive — it needs QMI direct mode, which suspends XIP. Under **stock
    MicroPython** `M0_RFMT` has PREFIX_LEN=0 and `M0_RCMD = 0xA0EB`, i.e. the chip is
    left sitting in **continuous-read (XIP) mode**, so `0x9F` cannot just be issued;
    the device must be returned to serial-command state first or XIP dies on return.
    (TE's firmware is the opposite: PREFIX_LEN=1, `M0_RCMD = 0x00EB`, so it re-sends
    the command every read and the chip is never in continuous mode.)
    
    Don't hand-roll the exit sequence — use the bootrom. Working recipe, script in
    `scratchpad/jedec.py`:
    
    1. `rom_table_lookup` = `mem16[0x16]` (ROM magic `'M','u',0x02` at `0x10`).
       Look up with **`RT_FLAG_FUNC_ARM_SEC = 0x0004`**; `'E','X'` → `flash_exit_xip`
       (`0xD65` on this A2 ROM). Codes are `c1 | (c2 << 8)`. `RT_FLAG_DATA = 0x0040`.
    2. MicroPython's inline asm has **no `blx`**; call the ROM pointer with a
       trampoline — `bl(CALL); b(DONE); label(CALL); bx(rN); label(DONE)` — so the
       `bl` leaves the return address in `lr` for the callee.
    3. `disable_irq()` → call `flash_exit_xip()` → `enable_irq()`. It returns with
       XIP working (03h reads, CLKDIV=12), so the interpreter can run normally
       between steps; IRQs only need to be off during the call itself, because an
       interrupt handler fetching from flash mid-call would fault.
    4. `disable_irq()` → RDID in a `@micropython.viper` routine (native code lives in
       RAM, so it keeps executing while XIP is down) → `enable_irq()`.
       Sequence: preserve CLKDIV/RXDELAY, set `EN`, poll `BUSY` clear, drain RX, set
       `ASSERT_CS0N`, then per byte push `DIRECT_TX` (`0x9F` then zeros) and pop
       `DIRECT_RX`; finally poll `BUSY`, deassert CS, clear `EN`. Bound every wait
       loop with a counter — a spin with interrupts off is an unrecoverable hang.
       The first RX byte is the one clocked in during the command byte; the ID starts
       at byte 1.
    
    Viper gotcha: `x & 0xffc00000` fails to compile with
    `ViperTypeError: can't do binary op between 'int' and 'object'` — constants above
    30 bits become objects. Use `(x >> 22) << 22`.
    
    **This leaves XIP in the slow 03h mode** (`M0_RFMT = 0x1000`, `M0_RCMD = 0x03`).
    Everything works, flash reads are just slower; only a hard reset re-runs boot2
    and restores fast QSPI XIP.
    
    #### ⚠️ Stock MicroPython's filesystem is oversized for this board
    
    The `RPI_PICO2` build targets the Pico 2's **4 MB** W25Q32 and reports
    `os.statvfs('/')` = 768 × 4096 = **3 MB** on this 2 MB part. Only the first
    ~1.9 MB of that region physically exists; beyond it the address wraps to flash 0
    and **overwrites the firmware image**. Fine for light use, but do not copy large
    files onto stock MicroPython while it is running on the EP-2350.
    
    ---
    
    ## 7. RP2350 platform notes
    
    Register bases and offsets used throughout (these differ from RP2040 — using
    RP2040 SIO offsets silently leaves pins driven):
    
    ```
    IO_BANK0     0x40028000   GPIOn STATUS @ +8n (OETOPAD=b13, OUTTOPAD=b9, INFROMPAD=b17)
                              GPIOn CTRL   @ +8n+4, FUNCSEL = CTRL[4:0]
    PADS_BANK0   0x40038000   GPIOn pad @ +4+4n (IE=b6, OD=b7, DRV=[5:4], PUE=b3, PDE=b2, SCH=b1)
    SIO          0xD0000000   GPIO_IN +0x004, GPIO_OUT +0x010, OUT_SET +0x018,
                              OUT_CLR +0x020, OUT_XOR +0x028, GPIO_OE +0x030,
                              OE_SET +0x038, OE_CLR +0x040
    I2C0 / I2C1  0x40090000 / 0x40098000   IC_CON +0x00, IC_TAR +0x04,
                              IC_DATA_CMD +0x10, IC_ENABLE +0x6c
    PIO0/1/2     0x50200000 / 0x50300000 / 0x50400000
                              CTRL +0, SMx PINCTRL @ +0xDC+0x18*x, SM0_ADDR +0xD4
                              PIO0_TXF0 = 0x50200010
    DMA          0x50000000   CHAN_ABORT +0x464
    FUNCSEL: 0 SPI, 1 UART, 2 I2C, 3 PWM, 4 SIO, 5 PIO0, 6 PIO1, 7 PIO2, 31 NULL
    ```
    
    **⚠️ RP2350-E9 erratum affects input probing.** A naive "internal pull-up vs
    pull-down" survey reports *every* pin as externally pulled high: with the
    internal pull-down enabled, a pad that has been high latches high. The reliable
    method is to drive the pin to the opposite state first to clear the latch, then
    release it to the internal pull and read:
    
    - external pull-up test: drive LOW → release with internal pull-DOWN → reads 1
    - external pull-down test: drive HIGH → release with internal pull-UP → reads 0
    
    Pull-*up*-only scans (as used for the buttons) are unaffected by the erratum.
    
    Also note `GPIO_IN` reads all-zero on a fresh MicroPython boot because RP2350
    pads default to input-disabled (`IE=0`); pins must be instantiated as `Pin`
    objects first.
    
    ---
    
    ## 8. Known open questions
    
    - **GP28**: VBAT/VSYS sense vs VBUS sense — not decisively settled.
    - **`get_vbus`**: probably a digital VBUS-present pin; no candidate identified.
    - **GP7, GP13, GP22, GP23, GP25**: unidentified (none drive an LED).
    - **Crystal frequency** — unconfirmed.
    - **QSPI flash CS pad location** — unconfirmed; needed for worst-case hardware
      recovery into ROM BOOTSEL. (The chip itself is identified: Winbond W25Q16JV,
      2 MB — see §6.)
    - Whether the power latch has a hardware auto-off in addition to the firmware
      timers.
    - A broadband ~13 kHz hump observed at the headphone jack that tracks mic gain —
      probably preamp noise shaped by the capture adapter; outside the audio band.

[2026-07-28 13:26:28] thinking: [not recorded in transcript]

[2026-07-28 13:26:29] tool use: Bash
    command: ls /home/agent/TE_ting_circuitpython/scripts | head -50

[2026-07-28 13:26:29] tool use: Bash
    command: ls -l /dev/ttyACM* /media/*/CIRCUITPY 2>&1 | head -20

[2026-07-28 13:26:29] tool result: Bash
    btn_monitor.py
    device_main.py
    device_mic_loop.py
    device_mic_passthru.py
    device_mic_rx.py
    device_mic_stream.py
    device_tone.py
    device_tone_slave.py
    dma_reset.py
    i2s_slave
    jedec.py
    knob_monitor.py
    led_test.py
    lock_test.py
    measure_freq.py
    mic_capfn.py
    mic_host.py
    mic_loop_verify.py
    mic_record.py
    mic_stream_host.py
    mic_to_hp.py
    play_loopback.py
    probe_phase.py
    __pycache__
    repl.py
    rp2pio_fixes
    rp.py
    rx_probe.py
    sweep_mclk.py
    t1_baseline.py
    t2b_adcdat_pull.py
    t2c_oe_tri.py
    t2_din.py
    t3_dout.py
    test_d2a_loop.py
    tone_autolock.py

[2026-07-28 13:26:29] tool result: Bash
    crw-rw---- 1 root dialout           166, 0 Jul 28 13:23 /dev/ttyACM0
    
    /media/timc/CIRCUITPY:
    total 2
    -rwxrwxr-x 1 timc removable_storage 183 Dec 31  1999 boot_out.txt
    -rwxrwxr-x 1 timc removable_storage  22 Dec 31  1999 code.py
    drwxrwxr-x 2 timc removable_storage 512 Dec 31  1999 lib
    drwxrwxr-x 2 timc removable_storage 512 Dec 31  1999 sd
    -rwxrwxr-x 1 timc removable_storage   0 Dec 31  1999 settings.toml

[2026-07-28 13:26:31] tool use: Bash
    command: cd /home/agent/TE_ting_circuitpython/scripts && sed -n 1,80p knob_monitor.py && echo ==== && sed -n 1,60p repl.py

[2026-07-28 13:26:31] tool result: Bash
    #!/usr/bin/env python3
    """Hunt for the EP-2350 volume knob: digital + analog at the same time.
    
    Digital: every GPIO except GP2 (power hold) and GP26-29 (claimed by the ADC)
    gets an internal pull-up; debounced GPIO_IN changes are streamed.  Catches a
    rotary encoder (two pins chattering in quadrature) or a switch.
    
    Analog: ADC0-3 (GP26-29) sampled continuously; a reading is reported whenever
    it moves more than THRESH counts from the last reported value.  Catches a
    potentiometer wiper.
    
    Usage:  python3 knob_monitor.py [seconds]
    """
    import sys, time, serial
    
    PORT = "/dev/ttyACM0"
    DUR = float(sys.argv[1]) if len(sys.argv) > 1 else 40.0
    
    DEV = """
    from machine import Pin, ADC, mem32
    import time
    SIO = 0xd0000000
    hold = Pin(2, Pin.OUT, value=1)
    DIG = [i for i in range(30) if i != 2 and not (26 <= i <= 29)]
    pins = [Pin(i, Pin.IN, Pin.PULL_UP) for i in DIG]
    MASK = 0
    for i in DIG:
        MASK |= 1 << i
    adcs = [ADC(i) for i in range(4)]
    THRESH = 400
    def rd():
        return mem32[SIO + 0x004] & MASK
    prev = rd()
    last = [a.read_u16() for a in adcs]
    t0 = time.ticks_ms()
    print("BASE %08x A %d %d %d %d" % (prev, last[0], last[1], last[2], last[3]))
    end = t0 + int(__DUR__ * 1000)
    while time.ticks_diff(end, time.ticks_ms()) > 0:
        v = rd()
        if v != prev:
            time.sleep_ms(5)
            v = rd()
            if v != prev:
                print("D %6d %08x %08x" % (time.ticks_diff(time.ticks_ms(), t0), v, v ^ prev))
                prev = v
        for j in range(4):
            c = adcs[j].read_u16()
            if abs(c - last[j]) > THRESH:
                print("A %6d %d %d" % (time.ticks_diff(time.ticks_ms(), t0), j, c))
                last[j] = c
        time.sleep_ms(2)
    print("DONE")
    """.replace("__DUR__", repr(DUR))
    
    DIG = [i for i in range(30) if i != 2 and not (26 <= i <= 29)]
    
    
    def fmt(s):
        p = s.split()
        try:
            if p[0] == "D":
                t, v, ch = int(p[1]), int(p[2], 16), int(p[3], 16)
                low = [i for i in DIG if not (v >> i) & 1]
                prs = [i for i in DIG if (ch >> i) & 1 and not (v >> i) & 1]
                rel = [i for i in DIG if (ch >> i) & 1 and (v >> i) & 1]
                bits = []
                if prs:
                    bits.append("->0 " + ",".join("GP%d" % i for i in prs))
                if rel:
                    bits.append("->1 " + ",".join("GP%d" % i for i in rel))
                return "t=%7.2fs DIG %-28s low=%s" % (
                    t / 1000.0, " ".join(bits), ",".join("GP%d" % i for i in low) or "-")
            if p[0] == "A":
                t, ch, val = int(p[1]), int(p[2]), int(p[3])
                return "t=%7.2fs ADC%d (GP%d) = %5d  %.3f V" % (
                    t / 1000.0, ch, 26 + ch, val, val * 3.3 / 65535)
        except (ValueError, IndexError):
            pass
        return s
    
    ====
    #!/usr/bin/env python3
    """Reliable raw-REPL exec helper for the EP-2350 over /dev/ttyACM0."""
    import sys, time, serial
    
    PORT = "/dev/ttyACM0"
    BAUD = 115200
    
    
    def _read_until(ser, ending, timeout=5.0):
        ending = ending if isinstance(ending, bytes) else ending.encode()
        buf = bytearray()
        deadline = time.time() + timeout
        while time.time() < deadline:
            n = ser.in_waiting
            if n:
                buf += ser.read(n)
                if buf.endswith(ending) or ending in buf:
                    return bytes(buf), True
                deadline = time.time() + timeout
            else:
                time.sleep(0.005)
        return bytes(buf), False
    
    
    def run(code, timeout=10.0):
        if isinstance(code, str):
            code = code.encode()
        with serial.Serial(PORT, BAUD, timeout=0.1) as ser:
            ser.write(b"\r\x03\x03")          # interrupt
            time.sleep(0.2)
            ser.reset_input_buffer()
            # Enter the raw REPL, and insist on it. If ctrl-A is missed the code
            # still *runs* -- the friendly REPL echoes and executes it -- but a
            # blank line inside a block silently truncates it, so a half-executed
            # script comes back looking like a successful run. Retry, then give up.
            for attempt in range(3):
                ser.write(b"\x01")            # ctrl-A -> raw REPL
                _, ok = _read_until(ser, b"raw REPL; CTRL-B to exit\r\n>", timeout=2.0)
                if ok:
                    break
                ser.write(b"\r\x03\x03")
                time.sleep(0.2)
                ser.reset_input_buffer()
            else:
                raise RuntimeError("could not enter raw REPL on " + PORT)
            ser.reset_input_buffer()
            ser.write(code)
            ser.write(b"\x04")                # ctrl-D -> execute
            # The reply is OK<stdout>\x04<stderr>\x04>. Accumulate the whole thing
            # rather than reading it a field at a time: a short, fast result can
            # land in a single read(), and splitting on the first \x04 found would
            # then throw away everything after it.
            resp = bytearray()
            deadline = time.time() + timeout
            while time.time() < deadline:
                n = ser.in_waiting
                if n:
                    resp += ser.read(n)
                    if resp.count(b"\x04") >= 2:
                        break

[2026-07-28 13:26:40] thinking: [not recorded in transcript]

[2026-07-28 13:26:41] tool use: Bash
    command: sed -n 80,200p knob_monitor.py; echo ====; sed -n 60,200p repl.py; echo ==== BTN; sed -n 1,40p btn_monitor.py

[2026-07-28 13:26:41] tool result: Bash
    def main():
        with serial.Serial(PORT, 115200, timeout=0.1) as ser:
            ser.write(b"\r\x03\x03")
            time.sleep(0.2)
            ser.reset_input_buffer()
            ser.write(b"\x01")
            time.sleep(0.3)
            ser.reset_input_buffer()
            ser.write(DEV.encode())
            ser.write(b"\x04")
            buf = b""
            deadline = time.time() + DUR + 15
            while time.time() < deadline:
                n = ser.in_waiting
                if n:
                    buf += ser.read(n)
                    while b"\n" in buf:
                        line, buf = buf.split(b"\n", 1)
                        s = line.decode(errors="replace").strip().lstrip("OK").strip()
                        if not s or s == ">":
                            continue
                        if s.startswith("DONE"):
                            print("--- done ---")
                            ser.write(b"\x02")
                            return
                        print(fmt(s), flush=True)
                else:
                    time.sleep(0.005)
            ser.write(b"\x03\x02")
    
    
    if __name__ == "__main__":
        try:
            main()
        except KeyboardInterrupt:
            pass
    ====
                        break
                    deadline = time.time() + timeout
                else:
                    time.sleep(0.005)
            ser.write(b"\x02")                # ctrl-B -> back to normal
            body = bytes(resp)
            if body.startswith(b"OK"):
                body = body[2:]
            parts = body.split(b"\x04")
            stdout = parts[0]
            stderr = parts[1] if len(parts) > 1 else b""
        return stdout.decode(errors="replace"), stderr.decode(errors="replace")
    
    
    if __name__ == "__main__":
        src = sys.stdin.read() if len(sys.argv) < 2 else open(sys.argv[1]).read()
        o, e = run(src)
        sys.stdout.write(o)
        if e.strip():
            sys.stderr.write("\n--- STDERR ---\n" + e)
    ==== BTN
    #!/usr/bin/env python3
    """Live GPIO change monitor for EP-2350 button hunting.
    
    Configures every GPIO except GP2 (power hold) as input with an internal
    pull-up, then streams every debounced change of GPIO_IN to stdout as
        t=<ms>  IN=<hex>  low=[pins reading 0]  changed=[pins that moved]
    
    Usage:  python3 btn_monitor.py [seconds]
    Ctrl-C to stop early; the device is left with GP2 still held high.
    """
    import sys, time, serial
    
    PORT = "/dev/ttyACM0"
    DUR = float(sys.argv[1]) if len(sys.argv) > 1 else 60.0
    
    DEV = """
    from machine import Pin, mem32
    import time
    SIO = 0xd0000000
    hold = Pin(2, Pin.OUT, value=1)
    pins = [Pin(i, Pin.IN, Pin.PULL_UP) for i in range(30) if i != 2]
    MASK = 0x3fffffff & ~(1 << 2)
    def rd():
        return mem32[SIO + 0x004] & MASK
    prev = rd()
    t0 = time.ticks_ms()
    print("BASE %08x" % prev)
    end = t0 + int(__DUR__ * 1000)
    while time.ticks_diff(end, time.ticks_ms()) > 0:
        v = rd()
        if v != prev:
            time.sleep_ms(8)          # debounce settle
            v = rd()
            if v != prev:
                print("%6d %08x %08x" % (time.ticks_diff(time.ticks_ms(), t0), v, v ^ prev))
                prev = v
        time.sleep_ms(2)
    print("DONE")
    """.replace("__DUR__", repr(DUR))

[2026-07-28 13:26:52] thinking: [not recorded in transcript]

[2026-07-28 13:26:53] agent:
    Only GP26–GP29 are ADC-capable on the RP2350A, and GP28/GP29 are already claimed (rail sense / volume), so GP26 and GP27 are the prime suspects. I'll write a monitor that samples all four while you work the handle.

[2026-07-28 13:27:17] tool use: Write
    file_path: /home/agent/TE_ting_circuitpython/scripts/handle_pot_monitor.py
    content:
        #!/usr/bin/env python3
        """Find the EP-2350 handle position potentiometer (CircuitPython build).
        
        The RP2350A only has four ADC-capable pins -- GP26 (A0), GP27 (A1), GP28 (A2)
        and GP29 (A3) -- so the handle pot has to be one of them.  GP28 is the rail
        sense divider and GP29 is the volume knob, which leaves GP26/GP27 as the
        likely candidates; all four are sampled anyway so nothing is assumed.
        
        The device samples the four ADCs plus the two digital handle switches
        (GP19 HANDLE_IN, GP20 HANDLE_OUT) every ~25 ms and streams them back.  The
        host prints a live line, walks you through a press/release script, and then
        ranks the channels by how much they moved and by how well they track the
        handle switches.
        
        Usage:  python3 handle_pot_monitor.py [seconds]      (default 30)
        """
        import sys, time, serial
        
        PORT = "/dev/ttyACM0"
        BAUD = 115200
        DUR = float(sys.argv[1]) if len(sys.argv) > 1 else 30.0
        
        DEV = """
        import board, analogio, digitalio, time
        NAMES = ("GP26", "GP27", "GP28", "GP29")
        adcs = [analogio.AnalogIn(p) for p in
                (board.GP26, board.GP27, board.GP28, board.GP29)]
        sw = []
        for p in (board.HANDLE_IN, board.HANDLE_OUT):
            d = digitalio.DigitalInOut(p)
            d.switch_to_input(digitalio.Pull.UP)
            sw.append(d)
        t0 = time.monotonic()
        end = t0 + __DUR__
        print("START")
        try:
            while time.monotonic() < end:
                ms = int((time.monotonic() - t0) * 1000)
                v = [a.value for a in adcs]
                print("S %d %d %d %d %d %d %d" % (ms, v[0], v[1], v[2], v[3],
                                                  sw[0].value, sw[1].value))
                time.sleep(0.025)
        finally:
            for a in adcs:
                a.deinit()
            for d in sw:
                d.deinit()
        print("DONE")
        """.replace("__DUR__", repr(DUR))
        
        NAMES = ["GP26/A0", "GP27/A1", "GP28/A2 (rail)", "GP29/A3 (volume)"]
        
        
        def script_for(t):
            """The press/release choreography, as a function of elapsed seconds."""
            f = t / DUR
            if f < 0.15:
                return "hands OFF the handle  (baseline)"
            if f < 0.35:
                return "press the handle IN slowly, all the way"
            if f < 0.50:
                return "HOLD it fully in"
            if f < 0.70:
                return "release it slowly, all the way out"
            if f < 0.85:
                return "press IN and hold half way, if you can"
            return "release, hands off"
        
        
        def analyse(samples):
            if len(samples) < 10:
                print("\nNot enough samples to analyse (%d)." % len(samples))
                return
            print("\n--- per-channel summary (%d samples) ---" % len(samples))
            cols = list(zip(*[s[1:5] for s in samples]))
            hin = [s[5] for s in samples]
            hout = [s[6] for s in samples]
            moved = hin.count(0) or hout.count(1)
            rows = []
            for i, col in enumerate(cols):
                lo, hi = min(col), max(col)
                span = hi - lo
                # Mean while the handle reads "out/at rest" vs "moved or seated".
                rest = [c for c, a, b in zip(col, hin, hout) if a == 1 and b == 0]
                used = [c for c, a, b in zip(col, hin, hout) if a == 0 or b == 1]
                sep = 0
                if rest and used:
                    sep = abs(sum(used) / len(used) - sum(rest) / len(rest))
                rows.append((span, sep, i, lo, hi))
                print("%-18s min %5d  max %5d  span %5d (%.3f V)  "
                      "handle-state separation %6.0f" %
                      (NAMES[i], lo, hi, span, span * 3.3 / 65535, sep))
            rows.sort(reverse=True)
            print()
            if not moved:
                print("The handle switches never changed -- was the handle actually "
                      "worked during the run?  Treat the ranking below with caution.")
            best = rows[0]
            if best[0] < 500:
                print("No channel moved more than %d counts: none of GP26-GP29 looks "
                      "like a handle pot." % best[0])
            else:
                print("Most movement: %s (span %d counts, %.2f V)." %
                      (NAMES[best[2]], best[0], best[0] * 3.3 / 65535))
        
        
        def main():
            samples = []
            phase = None
            with serial.Serial(PORT, BAUD, timeout=0.1) as ser:
                ser.write(b"\r\x03\x03")
                time.sleep(0.2)
                ser.reset_input_buffer()
                ser.write(b"\x01")
                time.sleep(0.3)
                ser.reset_input_buffer()
                ser.write(DEV.encode())
                ser.write(b"\x04")
                buf = b""
                deadline = time.time() + DUR + 15
                try:
                    while time.time() < deadline:
                        n = ser.in_waiting
                        if not n:
                            time.sleep(0.005)
                            continue
                        buf += ser.read(n)
                        while b"\n" in buf:
                            line, buf = buf.split(b"\n", 1)
                            s = line.decode(errors="replace").strip().lstrip("OK").strip()
                            if not s or s == ">":
                                continue
                            if s.startswith("DONE"):
                                raise StopIteration
                            if s.startswith("START"):
                                print("--- sampling for %.0f s ---" % DUR)
                                continue
                            if not s.startswith("S "):
                                print(s, flush=True)
                                continue
                            p = s.split()
                            try:
                                rec = [int(x) for x in p[1:8]]
                            except ValueError:
                                continue
                            samples.append(rec)
                            t = rec[0] / 1000.0
                            ph = script_for(t)
                            if ph != phase:
                                phase = ph
                                print("\n>>> %s" % ph.upper(), flush=True)
                            print("\rt=%5.1fs  GP26=%5d GP27=%5d GP28=%5d GP29=%5d  "
                                  "IN=%d OUT=%d" % (t, rec[1], rec[2], rec[3], rec[4],
                                                    rec[5], rec[6]), end="", flush=True)
                except (StopIteration, KeyboardInterrupt):
                    pass
                finally:
                    ser.write(b"\x03\x03\x02")
            print()
            analyse(samples)
        
        
        if __name__ == "__main__":
            main()

[2026-07-28 13:27:17] tool result: Write
    File created successfully at: /home/agent/TE_ting_circuitpython/scripts/handle_pot_monitor.py (file state is current in your context — no need to Read it back)

[2026-07-28 13:27:22] thinking: [not recorded in transcript]

[2026-07-28 13:27:23] agent:
    Quick baseline check first (no handle action needed):

[2026-07-28 13:27:29] tool use: Bash
    command:
        cd /home/agent/TE_ting_circuitpython && ~/agent_venv/bin/python - <<'EOF'
        import sys; sys.path.insert(0,"scripts")
        import repl
        o,e = repl.run("""
        import board, analogio, digitalio, time
        for nm, p in (("GP26",board.GP26),("GP27",board.GP27),("GP28",board.GP28),("GP29",board.GP29)):
            a = analogio.AnalogIn(p)
            vals = []
            for _ in range(16):
                vals.append(a.value)
                time.sleep(0.002)
            a.deinit()
            print(nm, min(vals), max(vals), sum(vals)//16)
        for nm, p in (("HANDLE_IN/GP19",board.HANDLE_IN),("HANDLE_OUT/GP20",board.HANDLE_OUT)):
            d = digitalio.DigitalInOut(p); d.switch_to_input(digitalio.Pull.UP)
            print(nm, d.value); d.deinit()
        """, timeout=15)
        print(o); print("ERR:", e)
        EOF
    description: Read baseline ADC values over REPL

[2026-07-28 13:27:33] tool result: Bash
    GP26 49564 49836 49672
    GP27 31703 32327 31879
    GP28 32247 32407 32362
    GP29 27510 27670 27616
    HANDLE_IN/GP19 True
    HANDLE_OUT/GP20 False
    
    ERR:

[2026-07-28 13:27:46] thinking: [not recorded in transcript]

[2026-07-28 13:27:50] agent:
    Baseline (handle at rest, `HANDLE_IN`=True, `HANDLE_OUT`=False):
    
    | pin | counts | volts |
    |---|---:|---:|
    | GP26/A0 | 49672 | 2.50 V |
    | GP27/A1 | 31879 | 1.60 V |
    | GP28/A2 (rail) | 32362 | 1.63 V |
    | GP29/A3 (volume) | 27616 | 1.39 V |
    
    GP26 and GP27 both sit at stable non-rail voltages, so neither is really "floating" — both are live candidates. Now I need the handle motion to tell which one tracks it.
    
    The test runs for 30 seconds and records all four channels plus the two handle switches. During it, please: **hands off for ~5 s, then slowly press the handle all the way in, hold ~3 s, slowly release, and repeat that press/release cycle until I say stop** — slow and continuous is what distinguishes a pot from a switch.

[2026-07-28 13:27:52] tool use: AskUserQuestion
    questions:
        [
          {
            "question": "Ready to start the 30-second handle capture?",
            "header": "Ready?",
            "multiSelect": false,
            "options": [
              {
                "label": "Start now",
                "description": "I'll launch the 30 s capture immediately — begin the hands-off/press/release cycle as described."
              },
              {
                "label": "Give me a moment",
                "description": "Hold off; I'll tell you when to start."
              }
            ]
          }
        ]

[2026-07-28 13:28:18] tool result: AskUserQuestion
    Your questions have been answered: "Ready to start the 30-second handle capture?"="Start now". You can now continue with these answers in mind.

[2026-07-28 13:28:21] tool use: Bash
    command: ~/agent_venv/bin/python scripts/handle_pot_monitor.py 30 2>&1 | tail -30
    description: Run handle pot capture
    timeout: 70000

[2026-07-28 13:28:53] tool result: Bash
    <persisted-output>
    Output too large (76.8KB). Full output saved to: /home/agent/.claude/projects/-home-agent-TE-ting-circuitpython/1b654052-359b-4c76-a397-09f16e1a835d/tool-results/bvi7g85s9.txt
    
    Preview (first 2KB):
    --- sampling for 30 s ---
    
    >>> HANDS OFF THE HANDLE  (BASELINE)
    
    t=  0.0s  GP26=49660 GP27=31607 GP28=32391 GP29=27638  IN=1 OUT=0
    t=  0.0s  GP26=49019 GP27=31751 GP28=32391 GP29=27510  IN=1 OUT=0
    t=  0.1s  GP26=49196 GP27=31815 GP28=32311 GP29=27622  IN=1 OUT=0
    t=  0.1s  GP26=49147 GP27=31815 GP28=32359 GP29=27638  IN=1 OUT=0
    t=  0.1s  GP26=49212 GP27=31847 GP28=32263 GP29=27638  IN=1 OUT=0
    t=  0.1s  GP26=49164 GP27=31687 GP28=32391 GP29=27638  IN=1 OUT=0
    t=  0.2s  GP26=49147 GP27=31799 GP28=32359 GP29=27638  IN=1 OUT=0
    t=  0.2s  GP26=49340 GP27=31703 GP28=32375 GP29=27638  IN=1 OUT=0
    t=  0.2s  GP26=49212 GP27=31735 GP28=32407 GP29=27638  IN=1 OUT=0
    t=  0.2s  GP26=49324 GP27=31703 GP28=32407 GP29=27622  IN=1 OUT=0
    t=  0.3s  GP26=49356 GP27=31671 GP28=32391 GP29=27638  IN=1 OUT=0
    t=  0.3s  GP26=49308 GP27=31639 GP28=32407 GP29=27638  IN=1 OUT=0
    t=  0.3s  GP26=49228 GP27=31655 GP28=32407 GP29=27638  IN=1 OUT=0
    t=  0.3s  GP26=49147 GP27=31735 GP28=32391 GP29=27622  IN=1 OUT=0
    t=  0.4s  GP26=49099 GP27=31815 GP28=32311 GP29=27638  IN=1 OUT=0
    t=  0.4s  GP26=49115 GP27=31783 GP28=32359 GP29=27638  IN=1 OUT=0
    t=  0.4s  GP26=49212 GP27=31639 GP28=32391 GP29=27622  IN=1 OUT=0
    t=  0.4s  GP26=49228 GP27=31879 GP28=32375 GP29=27622  IN=1 OUT=0
    t=  0.5s  GP26=49164 GP27=31799 GP28=32263 GP29=27638  IN=1 OUT=0
    t=  0.5s  GP26=49260 GP27=31639 GP28=32391 GP29=27622  IN=1 OUT=0
    t=  0.5s  GP26=49212 GP27=31591 GP28=32375 GP29=27638  IN=1 OUT=0
    t=  0.5s  GP26=49131 GP27=31799 GP28=32391 GP29=27622  IN=1 OUT=0
    t=  0.6s  GP26=49212 GP27=31927 GP28=32263 GP29=27638  IN=1 OUT=0
    t=  0.6s  GP26=49196 GP27=31639 GP28=32407 GP29=27622  IN=1 OUT=0
    t=  0.6s  GP26=49083 GP27=31735 GP28=32391 GP29=27574  IN=1 OUT=0
    t=  0.6s  GP26=49131 GP27=31767 GP28=32375 GP29=27574  IN=1 OUT=0
    t=  0.7s  GP26=49180 GP27=31751 GP28=32375 GP29=27638  IN=1 OUT=0
    t=  0.7s  GP26=49164 GP27=31671 GP28=32407 GP29=27622  IN=1 OUT=0
    t=  0.7s  GP26=49164 GP27=31687 GP28=32407 GP29=27622  IN=1 OUT=0
    t=  0.7s  GP26=49196 
    ...
    </persisted-output>

[2026-07-28 13:28:57] tool use: Bash
    command: tail -c 1200 /home/agent/.claude/projects/-home-agent-TE-ting-circuitpython/1b654052-359b-4c76-a397-09f16e1a835d/tool-results/bvi7g85s9.txt
    description: Show capture summary

[2026-07-28 13:28:57] tool result: Bash
    .7s  GP26=49228 GP27=31895 GP28=29815 GP29=27638  IN=0 OUT=1
    t= 29.8s  GP26=49244 GP27=31655 GP28=29863 GP29=27574  IN=0 OUT=1
    t= 29.8s  GP26=49164 GP27=31735 GP28=29863 GP29=27622  IN=0 OUT=1
    t= 29.8s  GP26=49276 GP27=31623 GP28=29863 GP29=27638  IN=0 OUT=1
    t= 29.8s  GP26=49340 GP27=31655 GP28=29879 GP29=27638  IN=0 OUT=1
    t= 29.9s  GP26=49260 GP27=31799 GP28=29863 GP29=27622  IN=0 OUT=1
    t= 29.9s  GP26=49228 GP27=31575 GP28=29863 GP29=27622  IN=0 OUT=1
    t= 29.9s  GP26=49180 GP27=31671 GP28=29783 GP29=27622  IN=0 OUT=1
    t= 29.9s  GP26=49260 GP27=31687 GP28=29879 GP29=27622  IN=0 OUT=1
    t= 30.0s  GP26=48987 GP27=31671 GP28=29863 GP29=27638  IN=0 OUT=1
    t= 30.0s  GP26=49180 GP27=31863 GP28=29863 GP29=27622  IN=0 OUT=1
    
    --- per-channel summary (1180 samples) ---
    GP26/A0            min 48907  max 49660  span   753 (0.038 V)  handle-state separation      1
    GP27/A1            min 31255  max 32135  span   880 (0.044 V)  handle-state separation      6
    GP28/A2 (rail)     min 29703  max 32423  span  2720 (0.137 V)  handle-state separation   2125
    GP29/A3 (volume)   min 27494  max 27686  span   192 (0.010 V)  handle-state separation      3
    
    Most movement: GP28/A2 (rail) (span 2720 counts, 0.14 V).

[2026-07-28 13:29:05] thinking: [not recorded in transcript]

[2026-07-28 13:29:10] tool use: Bash
    command:
        ~/agent_venv/bin/python - <<'EOF'
        import re
        p="/home/agent/.claude/projects/-home-agent-TE-ting-circuitpython/1b654052-359b-4c76-a397-09f16e1a835d/tool-results/bvi7g85s9.txt"
        txt=open(p).read()
        recs=[(float(a),int(b),int(c),int(d),int(e),int(f),int(g)) for a,b,c,d,e,f,g in
              re.findall(r"t=\s*([\d.]+)s\s+GP26=\s*(\d+) GP27=\s*(\d+) GP28=\s*(\d+) GP29=\s*(\d+)\s+IN=(\d) OUT=(\d)", txt)]
        print(len(recs))
        # downsample: average every 0.5s
        import statistics as st
        buckets={}
        for r in recs:
            k=round(r[0]*2)/2
            buckets.setdefault(k,[]).append(r)
        for k in sorted(buckets):
            b=buckets[k]
            m=lambda i: int(st.mean(x[i] for x in b))
            print("%5.1f  26=%5d 27=%5d 28=%5d 29=%5d  IN=%s OUT=%s" % (k,m(1),m(2),m(3),m(4),
                "".join(str(x[5]) for x in b[:4]), "".join(str(x[6]) for x in b[:4])))
        EOF
    description: Downsample and analyze trace

[2026-07-28 13:29:12] tool result: Bash
    1180
      0.0  26=49242 27=31746 28=32365 29=27622  IN=1111 OUT=0000
      0.5  26=49189 27=31732 28=32373 29=27624  IN=1111 OUT=0000
      1.0  26=49178 27=31735 28=32394 29=27611  IN=1111 OUT=0000
      1.5  26=49188 27=31787 28=32362 29=27632  IN=1111 OUT=0000
      2.0  26=49189 27=31726 28=32385 29=27619  IN=1111 OUT=0000
      2.5  26=49171 27=31711 28=32387 29=27623  IN=1111 OUT=0000
      3.0  26=49174 27=31761 28=32376 29=27629  IN=1111 OUT=0000
      3.5  26=49154 27=31738 28=32370 29=27610  IN=1111 OUT=0000
      4.0  26=49214 27=31731 28=32379 29=27622  IN=1111 OUT=0000
      4.5  26=49175 27=31771 28=32379 29=27611  IN=1111 OUT=0000
      5.0  26=49215 27=31737 28=32357 29=27620  IN=1111 OUT=0000
      5.5  26=49171 27=31716 28=31591 29=27612  IN=1111 OUT=1111
      6.0  26=49179 27=31734 28=30781 29=27606  IN=1111 OUT=1111
      6.5  26=49186 27=31745 28=29887 29=27620  IN=1111 OUT=1111
      7.0  26=49176 27=31737 28=29853 29=27607  IN=1111 OUT=1111
      7.5  26=49162 27=31763 28=29846 29=27612  IN=0000 OUT=1111
      8.0  26=49169 27=31771 28=29858 29=27612  IN=0000 OUT=1111
      8.5  26=49165 27=31778 28=29850 29=27622  IN=0000 OUT=1111
      9.0  26=49196 27=31783 28=29849 29=27622  IN=0000 OUT=1111
      9.5  26=49185 27=31743 28=29836 29=27607  IN=0000 OUT=1111
     10.0  26=49182 27=31762 28=29846 29=27607  IN=0000 OUT=1111
     10.5  26=49151 27=31735 28=29870 29=27618  IN=0000 OUT=1111
     11.0  26=49196 27=31763 28=30005 29=27610  IN=1111 OUT=1111
     11.5  26=49171 27=31767 28=30418 29=27622  IN=1111 OUT=1111
     12.0  26=49194 27=31764 28=31064 29=27616  IN=1111 OUT=1111
     12.5  26=49213 27=31710 28=31944 29=27616  IN=1111 OUT=1111
     13.0  26=49162 27=31742 28=32341 29=27623  IN=1111 OUT=0000
     13.5  26=49145 27=31715 28=32347 29=27602  IN=1111 OUT=0000
     14.0  26=49153 27=31761 28=32383 29=27598  IN=1111 OUT=0000
     14.5  26=49163 27=31747 28=32350 29=27619  IN=1111 OUT=0000
     15.0  26=49175 27=31726 28=31410 29=27610  IN=1111 OUT=1111
     15.5  26=49183 27=31766 28=30440 29=27604  IN=1111 OUT=1111
     16.0  26=49178 27=31778 28=29911 29=27623  IN=1111 OUT=1111
     16.5  26=49171 27=31757 28=29852 29=27621  IN=1111 OUT=1111
     17.0  26=49221 27=31737 28=29856 29=27633  IN=0000 OUT=1111
     17.5  26=49183 27=31735 28=29863 29=27617  IN=0000 OUT=1111
     18.0  26=49171 27=31747 28=29842 29=27612  IN=0000 OUT=1111
     18.5  26=49204 27=31721 28=29865 29=27600  IN=0000 OUT=1111
     19.0  26=49165 27=31778 28=29855 29=27607  IN=0000 OUT=1111
     19.5  26=49181 27=31729 28=29871 29=27620  IN=0000 OUT=1111
     20.0  26=49166 27=31749 28=29847 29=27606  IN=0000 OUT=1111
     20.5  26=49178 27=31733 28=29849 29=27626  IN=0000 OUT=1111
     21.0  26=49203 27=31765 28=29839 29=27623  IN=0000 OUT=1111
     21.5  26=49237 27=31745 28=29857 29=27615  IN=0000 OUT=1111
     22.0  26=49206 27=31733 28=29952 29=27605  IN=1111 OUT=1111
     22.5  26=49152 27=31732 28=30687 29=27617  IN=1111 OUT=1111
     23.0  26=49202 27=31748 28=31361 29=27601  IN=1111 OUT=1111
     23.5  26=49184 27=31765 28=32094 29=27618  IN=1111 OUT=1111
     24.0  26=49177 27=31753 28=32351 29=27622  IN=1111 OUT=0000
     24.5  26=49172 27=31726 28=32359 29=27610  IN=1111 OUT=0000
     25.0  26=49221 27=31728 28=32375 29=27617  IN=1111 OUT=0000
     25.5  26=49179 27=31747 28=32365 29=27617  IN=1111 OUT=0000
     26.0  26=49159 27=31749 28=32357 29=27600  IN=1111 OUT=0000
     26.5  26=49170 27=31779 28=32353 29=27628  IN=1111 OUT=0000
     27.0  26=49182 27=31735 28=32254 29=27618  IN=1111 OUT=0000
     27.5  26=49148 27=31743 28=30968 29=27610  IN=1111 OUT=1111
     28.0  26=49156 27=31751 28=29967 29=27615  IN=1111 OUT=1111
     28.5  26=49194 27=31761 28=29867 29=27625  IN=1111 OUT=1111
     29.0  26=49178 27=31736 28=29847 29=27622  IN=0000 OUT=1111
     29.5  26=49184 27=31738 28=29831 29=27626  IN=0000 OUT=1111
     30.0  26=49211 27=31693 28=29858 29=27622  IN=0000 OUT=1111

[2026-07-28 13:29:30] thinking: [not recorded in transcript]

[2026-07-28 13:29:34] agent:
    GP28 is the answer — and it's genuinely analog. It ramps smoothly through the travel (32370 at rest → ~29850 fully in), holds flat while held, and ramps back on release, with the ramp lasting exactly as long as you took to move the handle:
    
    ```
     5.0  28=32365   hands off
     5.5  28=31591   \
     6.0  28=30781    > pressing
     6.5  28=29887   /
     7.5  28=29846   fully in (HANDLE_IN=0)
    11.5  28=30418   \
    12.0  28=31064    > releasing
    12.5  28=31944   /
    13.0  28=32341   at rest
    ```
    
    GP26, GP27 and GP29 never moved beyond noise. But GP28 is currently mapped as `VOLTAGE_MONITOR`, so I need to rule out that this is just rail droop from the handle engaging the power path. Two checks — an LED load test (rail droop should show up there too) and holding at partial positions:

[2026-07-28 13:29:38] tool use: Bash
    command:
        ~/agent_venv/bin/python - <<'EOF'
        import sys; sys.path.insert(0,"scripts")
        import repl
        o,e = repl.run("""
        import board, analogio, digitalio, time
        a = analogio.AnalogIn(board.GP28)
        def rd(n=32):
            v=[a.value for _ in range(n)]
            return sum(v)//n
        leds=[]
        for p in (board.LED_WHITE1,board.LED_WHITE2,board.LED_WHITE3,board.LED_WHITE4,
                  board.LED_RED1,board.LED_RED2,board.LED_RED3,board.LED_RED4):
            d=digitalio.DigitalInOut(p); d.switch_to_output(False); leds.append(d)
        print("leds off", rd())
        for d in leds: d.value=True
        time.sleep(0.3)
        print("leds ON ", rd())
        for d in leds: d.value=False
        time.sleep(0.3)
        print("leds off", rd())
        for d in leds: d.deinit()
        a.deinit()
        """, timeout=20)
        print(o); print("ERR:",e)
        EOF
    description: LED load test on GP28

[2026-07-28 13:29:41] tool result: Bash
    leds off 32361
    leds ON  32361
    leds off 32367
    
    ERR:

[2026-07-28 13:29:51] thinking: [not recorded in transcript]

[2026-07-28 13:29:53] agent:
    All eight LEDs on = **0 counts** of change on GP28. It's insensitive to real current load, so the handle response is not rail droop — GP28 is a position sensor.
    
    One more confirmation that it holds intermediate positions (rather than just responding to motion). For the next 24 seconds, please: **hold the handle about a quarter in for ~5 s, then half in for ~5 s, then three-quarters for ~5 s, then fully in, then release.**

[2026-07-28 13:30:00] tool use: Bash
    command:
        ~/agent_venv/bin/python - <<'EOF' 2>&1 | tail -40
        import sys, time; sys.path.insert(0,"scripts")
        import serial
        DEV = """
        import board, analogio, digitalio, time
        a = analogio.AnalogIn(board.GP28)
        hi = digitalio.DigitalInOut(board.HANDLE_IN); hi.switch_to_input(digitalio.Pull.UP)
        ho = digitalio.DigitalInOut(board.HANDLE_OUT); ho.switch_to_input(digitalio.Pull.UP)
        t0=time.monotonic()
        while time.monotonic()-t0 < 24:
            v=[a.value for _ in range(32)]
            print("S %.1f %d %d %d %d %d" % (time.monotonic()-t0, sum(v)//32, min(v), max(v), hi.value, ho.value))
            time.sleep(0.2)
        a.deinit(); hi.deinit(); ho.deinit()
        print("DONE")
        """
        with serial.Serial("/dev/ttyACM0",115200,timeout=0.1) as ser:
            ser.write(b"\r\x03\x03"); time.sleep(0.2); ser.reset_input_buffer()
            ser.write(b"\x01"); time.sleep(0.3); ser.reset_input_buffer()
            ser.write(DEV.encode()); ser.write(b"\x04")
            buf=b""; end=time.time()+32
            while time.time()<end:
                n=ser.in_waiting
                if not n: time.sleep(0.01); continue
                buf+=ser.read(n)
                while b"\n" in buf:
                    line,buf=buf.split(b"\n",1)
                    s=line.decode(errors="replace").strip().lstrip("OK").strip()
                    if s.startswith("S "):
                        p=s.split()
                        print("t=%5s  GP28=%5s (min %5s max %5s)  IN=%s OUT=%s" % tuple(p[1:7]), flush=True)
                    elif s.startswith("DONE"): end=0
            ser.write(b"\x03\x03\x02")
        EOF
    description: Hold-position test on GP28
    timeout: 60000

[2026-07-28 13:30:27] tool result: Bash
    t= 16.1  GP28=32357 (min 32247 max 32407)  IN=1 OUT=0
    t= 16.3  GP28=32364 (min 32247 max 32423)  IN=1 OUT=0
    t= 16.5  GP28=31724 (min 31607 max 31767)  IN=1 OUT=1
    t= 16.7  GP28=31554 (min 31431 max 31575)  IN=1 OUT=1
    t= 16.9  GP28=31558 (min 31431 max 31575)  IN=1 OUT=1
    t= 17.1  GP28=31558 (min 31431 max 31591)  IN=1 OUT=1
    t= 17.3  GP28=31551 (min 31431 max 31591)  IN=1 OUT=1
    t= 17.5  GP28=31555 (min 31463 max 31607)  IN=1 OUT=1
    t= 17.7  GP28=31536 (min 31431 max 31591)  IN=1 OUT=1
    t= 17.9  GP28=31547 (min 31447 max 31575)  IN=1 OUT=1
    t= 18.1  GP28=31331 (min 31239 max 31383)  IN=1 OUT=1
    t= 18.3  GP28=30854 (min 30727 max 30871)  IN=1 OUT=1
    t= 18.5  GP28=30831 (min 30711 max 30887)  IN=1 OUT=1
    t= 18.7  GP28=30838 (min 30727 max 30887)  IN=1 OUT=1
    t= 18.9  GP28=30840 (min 30695 max 30903)  IN=1 OUT=1
    t= 19.1  GP28=30817 (min 30711 max 30855)  IN=1 OUT=1
    t= 19.3  GP28=30808 (min 30727 max 30871)  IN=1 OUT=1
    t= 19.5  GP28=30781 (min 30679 max 30839)  IN=1 OUT=1
    t= 19.7  GP28=30775 (min 30695 max 30807)  IN=1 OUT=1
    t= 19.9  GP28=30771 (min 30679 max 30807)  IN=1 OUT=1
    t= 20.1  GP28=30761 (min 30647 max 30791)  IN=1 OUT=1
    t= 20.3  GP28=30768 (min 30599 max 30807)  IN=1 OUT=1
    t= 20.5  GP28=30749 (min 30599 max 30791)  IN=1 OUT=1
    t= 20.7  GP28=30740 (min 30599 max 30775)  IN=1 OUT=1
    t= 20.9  GP28=30732 (min 30599 max 30759)  IN=1 OUT=1
    t= 21.1  GP28=30725 (min 30599 max 30759)  IN=1 OUT=1
    t= 21.3  GP28=30579 (min 30471 max 30615)  IN=1 OUT=1
    t= 21.5  GP28=29913 (min 29831 max 29943)  IN=1 OUT=1
    t= 21.7  GP28=29923 (min 29831 max 29943)  IN=1 OUT=1
    t= 21.9  GP28=29993 (min 29879 max 30039)  IN=1 OUT=1
    t= 22.1  GP28=30061 (min 29943 max 30119)  IN=1 OUT=1
    t= 22.3  GP28=30073 (min 29943 max 30103)  IN=1 OUT=1
    t= 22.5  GP28=30069 (min 29959 max 30103)  IN=1 OUT=1
    t= 22.7  GP28=30080 (min 29959 max 30119)  IN=1 OUT=1
    t= 22.9  GP28=30064 (min 29959 max 30119)  IN=1 OUT=1
    t= 23.1  GP28=30064 (min 29943 max 30103)  IN=1 OUT=1
    t= 23.3  GP28=30077 (min 29959 max 30119)  IN=1 OUT=1
    t= 23.5  GP28=30075 (min 29959 max 30119)  IN=1 OUT=1
    t= 23.7  GP28=30076 (min 29959 max 30103)  IN=1 OUT=1
    t= 23.9  GP28=30064 (min 29959 max 30103)  IN=1 OUT=1

[2026-07-28 13:30:37] thinking: [not recorded in transcript]

[2026-07-28 13:30:40] agent:
    Confirmed — it holds stable plateaus at intermediate positions:
    
    ```
    ~31550  quarter in     (held 1.5 s)
    ~30800  half in        (held 3 s, slight creep)
    ~29920  three-quarters (held 2.5 s)
    ~30070  fully in       (held 2 s)
    ```
    
    **The handle position pot is on GP28 (ADC2 / `board.A2`)** — the pin currently mapped as `VOLTAGE_MONITOR`. That earlier identification was wrong. Updating the board definition:

[2026-07-28 13:30:47] tool use: Edit
    replace_all: false
    file_path: /home/agent/TE_ting_circuitpython/circuitpython/ports/raspberrypi/boards/teenage_engineering_ep2350/pins.c
    old_string:
            // Rail sense through a resistive divider (VSYS/VBAT / 2).
            { MP_ROM_QSTR(MP_QSTR_GP28), MP_ROM_PTR(&pin_GPIO28) },
            { MP_ROM_QSTR(MP_QSTR_A2), MP_ROM_PTR(&pin_GPIO28) },
            { MP_ROM_QSTR(MP_QSTR_VOLTAGE_MONITOR), MP_ROM_PTR(&pin_GPIO28) },
    new_string:
            // Handle position potentiometer: how far the handle has been pressed in.
            // Continuous and monotonic over the travel, but it only swings across a
            // narrow part of the range -- roughly 32370 counts (1.63 V) with the
            // handle at rest down to 29850 counts (1.50 V) fully seated -- so scale it
            // rather than using the raw value. HANDLE_OUT (GP20) goes true early in
            // the travel, before the pot has moved far.
            // (Previously mapped as VOLTAGE_MONITOR; it is not a rail sense line --
            // switching all eight LEDs on moves it by zero counts.)
            { MP_ROM_QSTR(MP_QSTR_GP28), MP_ROM_PTR(&pin_GPIO28) },
            { MP_ROM_QSTR(MP_QSTR_A2), MP_ROM_PTR(&pin_GPIO28) },
            { MP_ROM_QSTR(MP_QSTR_HANDLE_POSITION), MP_ROM_PTR(&pin_GPIO28) },

[2026-07-28 13:30:47] tool result: Edit
    The file /home/agent/TE_ting_circuitpython/circuitpython/ports/raspberrypi/boards/teenage_engineering_ep2350/pins.c has been updated successfully. (file state is current in your context — no need to Read it back)

[2026-07-28 13:30:49] agent:
    Now the hardware notes:

[2026-07-28 13:30:50] tool use: Bash
    command: grep -n "GP28\|rail sense\|28 (ADC2)\|Volume knob" ep-2350-info.md

[2026-07-28 13:30:50] tool result: Bash
    39:| **28 (ADC2)** | analog rail sense (VSYS/VBAT ÷ 2, likely) | real divider, R_th ≈ 4.6 kΩ |
    40:| **29 (ADC3)** | **Volume knob** (potentiometer wiper) | analog, 0 → 3.29 V |
    88:Rail sensing: **GP28 (ADC2)** is the only genuine analog sense line — a real
    110:| Volume knob | not connected to the codec — it is an ADC input on GP29 (§1) |
    326:### Volume knob
    502:- **GP28**: VBAT/VSYS sense vs VBUS sense — not decisively settled.

[2026-07-28 13:30:52] tool use: Read
    file_path: /home/agent/TE_ting_circuitpython/ep-2350-info.md
    offset: 85
    limit: 8

[2026-07-28 13:30:52] tool result: Read
    85	**⚠️ Never call `machine.reset()` on this board** — it releases GP2, clearing the
    86	latch, and the unit powers off completely, requiring a physical power-on.
    87	
    88	Rail sensing: **GP28 (ADC2)** is the only genuine analog sense line — a real
    89	resistive divider (R_th ≈ 4.6 kΩ, consistent with 10k‖10k). VSYS/VBAT ÷ 2 is the
    90	leading interpretation (its reading moved −7.7 % when batteries were fitted), but
    91	VBUS ÷ N has not been fully excluded.
    92

[2026-07-28 13:30:56] tool use: Edit
    replace_all: false
    file_path: /home/agent/TE_ting_circuitpython/ep-2350-info.md
    old_string: | **28 (ADC2)** | analog rail sense (VSYS/VBAT ÷ 2, likely) | real divider, R_th ≈ 4.6 kΩ |
    new_string: | **28 (ADC2)** | **Handle position potentiometer** | analog, 1.63 V at rest → 1.50 V fully in |

[2026-07-28 13:30:56] tool result: Edit
    The file /home/agent/TE_ting_circuitpython/ep-2350-info.md has been updated successfully. (file state is current in your context — no need to Read it back)

[2026-07-28 13:31:02] tool use: Edit
    replace_all: false
    file_path: /home/agent/TE_ting_circuitpython/ep-2350-info.md
    old_string:
        Rail sensing: **GP28 (ADC2)** is the only genuine analog sense line — a real
        resistive divider (R_th ≈ 4.6 kΩ, consistent with 10k‖10k). VSYS/VBAT ÷ 2 is the
        leading interpretation (its reading moved −7.7 % when batteries were fitted), but
        VBUS ÷ N has not been fully excluded.
    new_string:
        Rail sensing: **there is no identified rail sense pin.** GP28 (ADC2) was long
        assumed to be one — it is a real divider, R_th ≈ 4.6 kΩ, and its reading moved
        −7.7 % when batteries were fitted — but it is actually the **handle position
        potentiometer** (§5). It is insensitive to load: switching all eight LEDs on
        moves it by zero counts. Whether the divider it sits in is referenced to VSYS
        (which would explain the battery-fitting shift) is unresolved.

[2026-07-28 13:31:02] tool result: Edit
    The file /home/agent/TE_ting_circuitpython/ep-2350-info.md has been updated successfully. (file state is current in your context — no need to Read it back)

[2026-07-28 13:31:04] tool use: Read
    file_path: /home/agent/TE_ting_circuitpython/ep-2350-info.md
    offset: 308
    limit: 30

[2026-07-28 13:31:04] tool result: Read
    308	
    309	| Button | GPIO | Sense |
    310	|--------|-----:|-------|
    311	| Side button — top (nearest handle) | **GP21** | 0 = pressed |
    312	| Side button — middle | **GP3** | 0 = pressed |
    313	| Side button — bottom | **GP1** | 0 = pressed |
    314	| Handle fully in (travel end-stop) | **GP19** | 0 = pressed |
    315	| Handle at rest / not held | **GP20** | 0 = released, 1 = held |
    316	
    317	**The handle is a two-stage switch.** GP19 and GP20 are separate switches on the
    318	same mechanism and change in sequence, with a dead band mid-travel where both
    319	read 1:
    320	
    321	- `GP20 == 1` is the earliest "user is touching the handle" signal — it fires
    322	  ~300 ms before GP19 confirms full insertion.
    323	- `GP19 == 0` means fully seated; this is what gates the power-on path.
    324	- Neither pin alone tells you the handle position — use the pair.
    325	
    326	Baseline `GPIO_IN` with the handle in and nothing pressed: `0x3ff7ffff`.
    327	
    328	### Volume knob
    329	
    330	A plain potentiometer across the 3V3 rail with its wiper on **GP29 = ADC3**. It
    331	is wired to the RP2350, **not** to the codec.
    332	
    333	```python
    334	from machine import ADC
    335	vol = ADC(3)                 # GP29
    336	level = vol.read_u16()       # 0..65535, full scale usable
    337	```

[2026-07-28 13:31:19] tool use: Edit
    replace_all: false
    file_path: /home/agent/TE_ting_circuitpython/ep-2350-info.md
    old_string:
        - Neither pin alone tells you the handle position — use the pair.
        
        Baseline `GPIO_IN` with the handle in and nothing pressed: `0x3ff7ffff`.
    new_string:
        - Neither pin alone tells you the handle position — use the pair, or better,
          read the position pot below.
        
        Baseline `GPIO_IN` with the handle in and nothing pressed: `0x3ff7ffff`.
        
        ### Handle position potentiometer
        
        **GP28 = ADC2** is a continuous position sensor for the handle, not the rail
        sense line it was long assumed to be (§2). Verified 2026-07-28 under
        CircuitPython with `scripts/handle_pot_monitor.py`.
        
        ```python
        import board, analogio
        handle = analogio.AnalogIn(board.HANDLE_POSITION)   # GP28 / A2
        frac = (32370 - handle.value) / 2520                # 0.0 at rest … 1.0 in
        ```
        
        | Handle | GP28 counts | volts |
        |---|---:|---:|
        | at rest | ≈ 32370 | 1.63 |
        | quarter in | ≈ 31550 | 1.59 |
        | half in | ≈ 30800 | 1.55 |
        | three-quarters | ≈ 29920 | 1.51 |
        | fully seated | ≈ 29850 | 1.50 |
        
        - **Usable swing is only ~2520 counts (≈ 4 % of full scale, 0.13 V).** Scale it;
          never use the raw value as a 16-bit control.
        - Monotonic and it *holds* intermediate positions — plateaus stay put for
          seconds within ±100 counts, and the sample-to-sample noise is ±80 counts, so
          averaging 16–32 samples is worth it.
        - The travel is squashed near the end: the last quarter of the mechanical
          travel is only ~70 counts, so the pot cannot resolve "nearly seated" vs
          "seated". Use GP19 for that.
        - GP20 (HANDLE_OUT) goes true very early — before the pot has moved much — so
          the pot's own movement is the better "user is touching the handle" trigger if
          you need travel proportionality rather than earliest detection.
        - Not load-sensitive: all eight LEDs on moves it 0 counts.
        - GP26 (A0) and GP27 (A1) sit at stable 2.50 V and 1.60 V respectively but do
          not respond to the handle; still unidentified.

[2026-07-28 13:31:19] tool result: Edit
    The file /home/agent/TE_ting_circuitpython/ep-2350-info.md has been updated successfully. (file state is current in your context — no need to Read it back)

[2026-07-28 13:31:22] tool use: Edit
    replace_all: false
    file_path: /home/agent/TE_ting_circuitpython/ep-2350-info.md
    old_string: - **GP28**: VBAT/VSYS sense vs VBUS sense — not decisively settled.
    new_string:
        - **Rail sensing**: no pin identified. GP28 turned out to be the handle position
          pot (§5), so nothing is known to read VBAT/VSYS/VBUS as an analog level.

[2026-07-28 13:31:23] tool result: Edit
    The file /home/agent/TE_ting_circuitpython/ep-2350-info.md has been updated successfully. (file state is current in your context — no need to Read it back)

[2026-07-28 13:31:25] tool use: Bash
    command: grep -n "GP26\|GP27\|unidentified" ep-2350-info.md | sed -n 1,20p

[2026-07-28 13:31:25] tool result: Bash
    19:| 7 | unidentified | — |
    25:| 13 | unidentified | — |
    34:| 22, 23 | unidentified | — |
    36:| 25 | unidentified (not ADC-capable) | — |
    361:- GP26 (A0) and GP27 (A1) sit at stable 2.50 V and 1.60 V respectively but do
    362:  not respond to the handle; still unidentified.
    543:- **GP7, GP13, GP22, GP23, GP25**: unidentified (none drive an LED).

[2026-07-28 13:31:28] tool use: Bash
    command: sed -n 37,39p ep-2350-info.md

[2026-07-28 13:31:28] tool result: Bash
    | 26 (ADC0) | floating / unconnected | — |
    | 27 (ADC1) | floating / unconnected | — |
    | **28 (ADC2)** | **Handle position potentiometer** | analog, 1.63 V at rest → 1.50 V fully in |

[2026-07-28 13:31:32] tool use: Edit
    replace_all: false
    file_path: /home/agent/TE_ting_circuitpython/ep-2350-info.md
    old_string:
        | 26 (ADC0) | floating / unconnected | — |
        | 27 (ADC1) | floating / unconnected | — |
    new_string:
        | 26 (ADC0) | unidentified — sits at a stable 2.50 V, does not track the handle | — |
        | 27 (ADC1) | unidentified — sits at a stable 1.60 V, does not track the handle | — |

[2026-07-28 13:31:32] tool result: Edit
    The file /home/agent/TE_ting_circuitpython/ep-2350-info.md has been updated successfully. (file state is current in your context — no need to Read it back)

[2026-07-28 13:31:35] agent:
    Now saving this to memory, since it corrects a pin identification that's easy to trip over:

[2026-07-28 13:31:43] tool use: Write
    file_path: /home/agent/.claude/projects/-home-agent-TE-ting-circuitpython/memory/ep2350-handle-position-pot.md
    content:
        ---
        name: ep2350-handle-position-pot
        description: GP28/ADC2 on the EP-2350 is the handle position potentiometer, not a rail sense line
        metadata:
          type: project
        ---
        
        **GP28 (ADC2 / `board.A2`) is the handle position potentiometer**, verified
        2026-07-28 under CircuitPython with `scripts/handle_pot_monitor.py`. It was
        previously mapped as `VOLTAGE_MONITOR` / "rail sense (VSYS ÷ 2)" in `pins.c` and
        `ep-2350-info.md`; both are now corrected, and the board def exposes it as
        `board.HANDLE_POSITION` (needs a firmware rebuild + flash to appear —
        `board.GP28` works today).
        
        **Why:** the RP2350A only has four ADC pins (GP26–GP29), GP29 is the volume knob,
        and GP26/GP27 do not move with the handle, so GP28 was the only candidate — and
        it tracks the handle continuously, holding stable plateaus at partial travel.
        Ruled out rail droop: switching all eight LEDs on moves it **0 counts**.
        
        **How to apply:**
        - Swing is only **~2520 counts** (32370 at rest → 29850 fully in, ≈ 0.13 V).
          Scale it; never treat the raw 16-bit value as the control range.
        - Noise is ±80 counts — average 16–32 samples.
        - The last quarter of mechanical travel is only ~70 counts, so use GP19
          (`HANDLE_IN`) to detect "fully seated", not the pot.
        - No pin is now known to sense the battery/USB rail.
        
        See [[ep2350-dangerous-pins]] and [[ep2350-repl-workflow]].

[2026-07-28 13:31:43] tool result: Write
    File created successfully at: /home/agent/.claude/projects/-home-agent-TE-ting-circuitpython/memory/ep2350-handle-position-pot.md

[2026-07-28 13:31:45] tool use: Read
    file_path: /home/agent/.claude/projects/-home-agent-TE-ting-circuitpython/memory/MEMORY.md

[2026-07-28 13:31:45] tool result: Read
    <system-reminder>This memory is 5 days old. Memories are point-in-time observations, not live state — claims about code behavior or file:line citations may be outdated. Verify against current code before asserting as fact.</system-reminder>
    1	- [Audio test rig](audio-test-rig.md) — headphone out wired to USB adapter mic-in (`arecord`, card number shifts); speakers next to the EP-2350 mic give an acoustic stimulus via `aplay`.
    2	- [EP-2350 REPL workflow](ep2350-repl-workflow.md) — driving the board over the raw REPL, and why board state vanishes between serial connections.
    3	- [EP-2350 dangerous pins](ep2350-dangerous-pins.md) — GP2 is POWER_HOLD and kills the board; which pins are actually safe to poke.
    4	- [EP-2350 firmware build](ep2350-firmware-build.md) — the exact make invocation, the venv it needs, and who flashes.
    5	- [CIRCUITPY has its own module copies](circuitpy-has-its-own-module-copies.md) — the board imports `ep2350_codec.py` from CIRCUITPY; host edits do nothing until copied over.
    6	- [Output level ceiling — RESOLVED](ep2350-output-level-ceiling.md) — the "quiet, clips at −12 dBFS" output was the R80 PDB_DAC driver bug (DAC output stage powered down); fixed 2026-07-22, pre-fix jack measurements are invalid.
    7	- [Ask before installing system packages](ask-before-installing-system-packages.md) — no sudo here; request apt installs instead of unpacking debs.
    8	- [Mic "wind" subsonic fix](mic-wind-subsonic-fix.md) — passthrough wind is mic DC/bias-drift; fixed with codec ADC biquad HPF (`configure_adc_highpass`), not a host filter.
    9	- [Static is the USB capture dongle](static-is-usb-capture-dongle.md) — the recording hiss is mostly the card-3 dongle's own noise floor at max capture gain, not the EP-2350.
    10	- [Demo is a 4-effect switcher](ep2350-demo-multi-effect.md) — code_ep2350_demo.py: pitch up/down + reverb + echo, TOP selects, MIDDLE toggles, red LEDs show state.
    11

[2026-07-28 13:31:49] tool use: Edit
    replace_all: false
    file_path: /home/agent/.claude/projects/-home-agent-TE-ting-circuitpython/memory/MEMORY.md
    old_string: - [Demo is a 4-effect switcher](ep2350-demo-multi-effect.md)
    new_string:
        - [Handle position pot is GP28](ep2350-handle-position-pot.md) — GP28/ADC2 is the handle travel pot, not rail sense; narrow ~2520-count swing.
        - [Demo is a 4-effect switcher](ep2350-demo-multi-effect.md)

[2026-07-28 13:31:49] tool result: Edit
    The file /home/agent/.claude/projects/-home-agent-TE-ting-circuitpython/memory/MEMORY.md has been updated successfully. (file state is current in your context — no need to Read it back)

[2026-07-28 13:32:02] agent:
    **The handle pot is on GP28 — ADC2, `board.A2`.** It was the pin already mapped as `VOLTAGE_MONITOR`, which is why it never showed up as a candidate.
    
    How it was pinned down:
    - The RP2350A only has four ADC pins (GP26–GP29), so the search space was small. GP29 is the volume knob; GP26/GP27 sit at stable 2.50 V / 1.60 V but did not budge during any handle motion.
    - GP28 tracked the handle continuously — smooth ramps whose duration matched how slowly you moved it, and flat plateaus at quarter/half/three-quarter positions held for seconds.
    - Ruled out rail droop from the handle engaging the power path: switching all eight LEDs on (real current) moves GP28 by **0 counts**.
    
    Calibration: **32370 counts (1.63 V) at rest → 29850 (1.50 V) fully seated**. Two caveats worth knowing:
    - The usable swing is only ~2520 counts, about 4% of full scale, with ±80 counts of noise — scale it and average 16–32 samples.
    - The last quarter of travel is only ~70 counts, so the pot can't distinguish "nearly in" from "seated". Keep using GP19/`HANDLE_IN` for that.
    
    Changes made:
    - `circuitpython/ports/raspberrypi/boards/teenage_engineering_ep2350/pins.c:104` — `VOLTAGE_MONITOR` replaced with `HANDLE_POSITION` on GP28, with the calibration in a comment. This needs a firmware rebuild and flash before `board.HANDLE_POSITION` exists; `board.GP28` / `board.A2` works right now.
    - `ep-2350-info.md` — new §5 "Handle position potentiometer" with the calibration table, GPIO map row corrected, and the rail-sensing claim retracted (no pin is now known to sense VBAT/VSYS/VBUS).
    - `scripts/handle_pot_monitor.py` — the discovery script, reusable if you want to re-measure the endpoints.
    
    One loose end I did not chase: the old note that GP28's reading shifted −7.7% when batteries were fitted. That suggests its divider may be referenced to VSYS rather than 3V3, which would make the position reading drift slightly with supply. Worth a check if you build anything precise on it.