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BOM: WT61 burnt out on fitting; facts from datasheet v24-0429

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Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DDwfd6Ki8UfG4hK6W5YpJz
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Mikkeli Matlock
2026-10-12 15:25:32 +09:00
parent 4ac775a13d
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@@ -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