From d4d5edb2fc05248d29c38562bb9040c89b9560d3 Mon Sep 17 00:00:00 2001 From: Mikkeli Date: Mon, 12 Oct 2026 15:25:32 +0900 Subject: [PATCH] BOM: WT61 burnt out on fitting; facts from datasheet v24-0429 Co-Authored-By: Claude Opus 5.5 Claude-Session: https://claude.ai/code/session_01DDwfd6Ki8UfG4hK6W5YpJz --- docs/BOM.md | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/docs/BOM.md b/docs/BOM.md index c01a07f..17f0cec 100644 --- a/docs/BOM.md +++ b/docs/BOM.md @@ -98,7 +98,7 @@ type: reference ## WitMotion WT61 IMU -**Status: being fitted (2026-10-12)** on Dupont wires, moved from the smart-serow motorcycle unit, where an Arduino read it. Final mounting and connector to follow. +**Status: module lost (2026-10-12).** The unit moved from smart-serow shorted and burnt out on first power-up on Dupont wires; cause unknown. Needs a replacement. Everything below still applies to one. | Field | Value | |-------|-------| @@ -108,9 +108,10 @@ type: reference | **Interface** | TTL UART on the 40-pin header: **UART1, `/dev/ttyTHS1`** (free: no console or getty on it). The header I²C stays free for other sensors | | **Protocol** | 11-byte packets, `0x55` header: accel `0x51`, gyro `0x52`, angle `0x53`, each three int16 values + temperature + checksum. Reference: smart-serow `arduino/IMU.md` | | **Rate** | Planned 115200 baud / 100 Hz (factory default) | -| **Power** | 3.3 V from header pin 1. Datasheet: 3.3–5 V input through an onboard regulator, **< 10 mA** | +| **Power** | 3.3 V from header pin 1. Datasheet v24-0429: 3.3–5.5 V, **5 mA** working (5 V), 39 µA asleep; data valid ~1 s after power-up | | **Range** | ±16 g, ±2000 °/s; roll and yaw ±180°, pitch ±90°. No magnetometer | -| **Datasheet** | `~/infra/kb/inbox/engineer/raw/WT61_Datasheet.pdf` (raw, not yet in the KB) | +| **Datasheet** | v24-0429: `/mnt/wdelem/dropzone/WT61-datasheet-240429.pdf`. Older: `~/infra/kb/inbox/engineer/raw/WT61_Datasheet.pdf` (raw, not yet in the KB) | +| **Module pins (bare module, 12 pads)** | 2, 11 VCC · 5, 8 GND · 3 RX · 4 TX · 6 SWIM (programming) · 1, 7, 9, 10, 12 not connected. A breakout board's labels take precedence | ### Wiring (40-pin header) @@ -150,7 +151,9 @@ Everything sits in header pins 1–10, so one 2×5 connector can carry it. Pins - **Realign:** a press levels the frame to gravity (the mounting rotation, from averaged accelerometer readings) and sends `FF AA 52` to zero yaw. The result is stored on disk, not redone every drive. Refuse while moving (gyro or GPS speed); record raw data plus a realign event, so a bad alignment can be corrected afterwards. Align on level ground: a slope becomes part of the mount. -- I²C mode (`FF AA 62`) exposes the raw MPU6050 only (no angles) and needs 4.7 kΩ pull-ups. Not used. +- I²C mode (`FF AA 62`) exposes the raw MPU6050 only (no angles) and needs 4.7 kΩ pull-ups. Not used; v24-0429 lists SDA/SCL as not connected. +- **No reverse-polarity protection is documented.** A 4-way Dupont housing put on the wrong way round swaps VCC and GND. Check VCC and GND + with a meter before first power-up. ## RTC backup battery