AHRS

Component Type: Program

Status: Implemented

Overview

CProgAhrs - AHRS sensor-fusion program. Fuses an accelerometer IO and a gyroscope IO (x-io Fusion library, Madgwick’s revised algorithm) into world-frame linear acceleration: gravity removed, Z up, m/s².

accelerometer + gyroscope in (float, dim >= 3; extra elements such as a trailing temperature are ignored), optional magnetometer for absolute heading (9-DOF; shares the rejection threshold with the accelerometer)
world-frame linear acceleration out (float virt, dim 3, notify)
runtime-writable filter parameters (via a writable config IO)

Data types

The x-io Fusion library computes in float only (not type-parameterised), so all bound IOs must be float. For other sources convert upstream with adjust — the program expects m/s² and rad/s.

Implementation

The program is notifier-driven (no thread). Each accelerometer notification caches the latest sample (converted to g). Each gyroscope notification (converted to deg/s, gyro-offset-corrected) advances the AHRS with a dt measured from the monotonic clock (clamped to [1 ms, 100 ms]; outside the window the nominal 1/rate is used) and writes the earth acceleration (in m/s²) to the output IO. No output is produced until the first accelerometer sample has been seen.

Configuration

Kconfig

CONFIG_DAWN_PROG_AHRS: enables the AHRS program. Depends on CONFIG_LIB_MADGWICK.

Descriptor

- id: ahrs1
  type: ahrs
  config:
    accel: *accel0          # float sensor/virt IO, notify
    gyro: *gyro0            # float sensor/virt IO, notify
    mag: *mag0              # optional magnetometer (9-DOF)
    output: *fused_src      # float virt IO (shape owned by the program)
    params:
      gain: 0.5             # filter gain
      accel_rejection: 10.0 # acceleration rejection threshold [deg]
      recovery_period: 5.0  # recovery trigger period [s]
      rate: 50.0            # nominal sample rate [Hz]

params is a single 4-float config item. A writable config IO with objcfg_ref: params makes it runtime-writable; out-of-range writes are rejected (gain 0-10, accel_rejection 0-90, recovery_period 0-60, rate 1-1000).