The CHR-6dm is an Attitude and Heading Reference System (AHRS) from CH
Robotics that uses a powerful 32-bit STM32F103T8 ARM Cortex M3 running at 64 MHz
to process data from an ADXL335 three-axis accelerometer, a LP510AL pitch/roll rate
gyro, a LY510ALH yaw rate gyro, and an HMC5843 three-axis digital magnetic
compass. An on-board Extended Kalman Filter (EKF) produces estimates for yaw,
pitch, and roll angles and angle rates, which can be streamed at up to 300 Hz
over a simple TTL (3.3V with 5V-tolerant pins) serial interface or transmitted
upon request along with raw data from any of the board’s sensors. Regardless of
the transmission rate, internal angle estimates are maintained at over 500 Hz to
ensure long-term accuracy. A USB-to-serial adapter can
be used to connect the IMU to a computer running the free AHRS Interface PC
application, which can be used for data visualization, board calibration, and
AHRS settings configuration.
The CHR-6dm simplifies system integration by providing a number of automatic
calibration routines, including rate gyro bias calibration, magnetometer hard
and soft iron calibration, and accelerometer “zeroing” to compensate for
AHRS-platform misalignment. All calibration routines are triggered by sending
simple commands over the serial interface.
An on-board 3.3V regulator further simplifies integration. With possible
input voltages ranging from 3.3 to 12 V and with 5V-tolerant I/O pins, the
CHR-6dm can easily be integrated into a wide range of systems. The board also
provides a +3.3V output that can deliver up to 400 mA to peripheral devices. The
board’s pins have a 0.1" spacing, so they will work with standard 0.1" headers and breadboards.
This tiny (1.0"×0.96") orientation sensor weighs just 2.7 g, making it well
suited for unmanned aerial vehicle (UAV) navigation.
For a less expensive version of this board that does not include a 3-axis
magnetic compass, please see the CHR-6d inertial measurement