cu-ahrs

cu-ahrs is a Copper task that runs the uf-ahrs Mahony filter on standardized IMU payloads (with optional magnetometer) to output roll, pitch, and yaw in radians.

Axis convention

• Body frame matches the aerospace/NED convention: +X forward, +Y right, +Z down.
• Positive rotations follow the right-hand rule about each axis:
  • Roll: right wing down is positive (rotation about +X).
  • Pitch: nose up is positive (rotation about +Y).
  • Yaw: clockwise when looking down along +Z (turning right) is positive.
• Accelerometer readings are expected to include gravity (a level IMU yields roughly [0, 0, +9.81] m/s²).

The task outputs absolute filter orientation (no startup zero reference).

Bare-metal RP2350 demos

Two RP2350 no-std options mirroring mpu9250-whoami:

• examples/rp2350_ahrs.rs: stand-alone loop (no Copper runtime) printing RPY.
• examples/rp2350_copper.rs + examples/rp_copperconfig.ron: full Copper app wiring resources::RpMpu9250Source -> cu_ahrs::CuAhrs -> tasks::RpySink, with SPI/CS/delay provided by a normal Copper resource bundle and a dummy magnetometer source feeding the optional mag input.

# Host clippy/tests remain on the default host target.
cargo clippy -p cu-ahrs
cargo test -p cu-ahrs

# RP2350 firmware builds (no_std): opt-in config/target.
CARGO_CONFIG=.cargo/config.rp2350.toml cargo run --no-default-features --features rp2350-demo --example rp2350_copper

The RP2350 build uses thumbv8m.main-none-eabihf and memory.x matching the original mpu9250-whoami app. It prints RPY (radians) over RTT/defmt. Wire your MPU9250 to SPI1 pins (SCK=GPIO10, MOSI=GPIO11, MISO=GPIO12, CS=GPIO13) on Pico 2W-class boards and flash with probe-rs.