Triki

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IMU streaming ​

The Triki streams raw accelerometer + gyroscope over BLE once you send a multi-byte start command on RX. Verified live here.

Start the stream ​

Write to RX …0002:

20 10 00 D0 07 68 00 03

(68 00 = 104 → ~104 Hz sample rate.)

Stream format ​

The device then pushes 14-byte frames on TX …0003:

offset  0    2     4     6      8      10     12
        22 00 gyroX gyroY gyroZ accelX accelY accelZ
header ─┘     └──────────────── 6 × int16 LE ──────┘

Bytes 0–1 are the 22 00 header; the six axes follow as signed int16, little-endian at offsets 2 / 4 / 6 (gyro) and 8 / 10 / 12 (accel). Scales:

  • gyro / 14.286 → deg/s — LSM6DSL ±2000 dps (70 mdps/LSB). The older 131.0 was an MPU-6050 ±250 dps value carried over from notes; it under-rotated ~9×.
  • accel / 2048.0 → g — LSM6DSL ±16 g (flat token reads +2048 = 1 g).

Frames arrive in bursts at ~104 Hz (the default; the rate is selectable — see Sample rate).

Startup behaviour ​

  • The first ~20 frames after start are noise — discard them before trusting the data (to be verified).
  • For a clean gravity/zero baseline, let the token sit flat and still for a moment before sending the start command.
  • There is no stop opcode: the stream ends when you disconnect.

Verification ​

Under shaking, gyro swings ±10000+, and the accel axis aligned with gravity reads ≈ +2048 (= 1 g) — decode confirmed at ~104 Hz. Reader: tools/ble_imu_stream.py (see Tooling).

This is sufficient to use the token as a motion controller — recover orientation via 6-axis gyro + accel fusion. The triki-controller package ships two interchangeable filters: Madgwick (one gain, beta) and VQF (accel low-pass time constant tauAcc; ported from VQF by Daniel Laidig, MIT). Both produce the same right-handed [w, x, y, z] frame and, being magnetometer-free, drift in yaw — re-zero heading as needed.

Note: the single-byte opcodes (0x05 / 0x07 / 0x09 / …) are a separate diagnostic/management interface — raw IMU is NOT there; it only comes from the start-stream command above.