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fix(bridge): reverse SDL axis remapping to recover Nintendo-native IMU axes

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SDL's hidapi_switch.c SendSensorUpdate() remaps Nintendo's raw sensor axes
to match PlayStation convention before emitting SDL sensor events:
  SDL_X = -Nintendo_Y, SDL_Y = +Nintendo_Z, SDL_Z = -Nintendo_X

This commit reverses that transform so the values sent to the Pico are in
Nintendo's native coordinate frame:
  Nintendo_X_raw = -SDL_Z
  Nintendo_Y_raw = -SDL_X
  Nintendo_Z_raw = +SDL_Y

Same mapping for gyro (bias subtraction happens before axis reversal).
Confirmed from SDL3 hidapi_switch.c source (SDL2 uses same SDL3 backend).
This commit is contained in:
Joey Yakimowich-Payne 2026-03-16 12:00:44 -06:00
commit a55b3786c1
1 changed files with 15 additions and 6 deletions
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21
src/switch_pico_bridge/controller_uart_bridge.py
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@ -1322,13 +1322,22 @@ def handle_sensor_update(
uz -= bz
ax, ay, az = ctx.last_accel
# SDL (hidapi_switch.c SendSensorUpdate) remaps Nintendo's native axes to match
# PlayStation convention before emitting sensor events:
# SDL_out[0] (X) = -(Nintendo_Y * scale)
# SDL_out[1] (Y) = +(Nintendo_Z * scale)
# SDL_out[2] (Z) = -(Nintendo_X * scale)
# We must reverse that to recover Nintendo-native values:
# Nintendo_X = -SDL_Z
# Nintendo_Y = -SDL_X
# Nintendo_Z = +SDL_Y
sample = IMUSample(
accel_x=convert_accel_to_raw(ax),
accel_y=convert_accel_to_raw(ay),
accel_z=convert_accel_to_raw(az),
gyro_x=convert_gyro_to_raw(ux, config.gyro_scale),
gyro_y=convert_gyro_to_raw(uy, config.gyro_scale),
gyro_z=convert_gyro_to_raw(uz, config.gyro_scale),
accel_x=convert_accel_to_raw(-az),
accel_y=convert_accel_to_raw(-ax),
accel_z=convert_accel_to_raw(ay),
gyro_x=convert_gyro_to_raw(-uz, config.gyro_scale),
gyro_y=convert_gyro_to_raw(-ux, config.gyro_scale),
gyro_z=convert_gyro_to_raw(uy, config.gyro_scale),
)
ctx.imu_samples.append(sample)