CHR-6d Inertial Measurement Unit

This six-DOF IMU from CH Robotics packs three accelerometer axes, three gyroscope axes, and a STM32F103T8 ARM Cortex processor into a tiny, 0.8" x 0.7" x 0.1" board. The small size and light weight (1.5 g) make the board well suited for unmanned aerial vehicle (UAV) navigation. The integrated 32-bit MPU takes 16-bit readings of the sensors, applies a customizable filter, and reports the results via a TTL serial interface. The Cortex’s programming pins are exposed, and the firmware is open-source.

	Description		Specifications (9)		Pictures (3)		Resources (8)		FAQs (0)

Discontinuation Notice: This module has been replaced by the much more capable CHR-UM6-LT orientation sensor. For an alternative IMU, please consider the Pololu MinIMU-9.

Overview

The CH Robotics CHR-6d inertial measurement unit (IMU) uses a 32-bit STM32F103T8 ARM Cortex processor to take 16-bit ADC readings from an ADXL335 three-axis accelerometer, a LP510AL pitch/roll rate gyro, and a LY510ALH yaw rate gyro, providing a full six degree of freedom (6-DOF) measurement solution. The Cortex processor applies a customizable finite impulse response (FIR) digital filter to help reduce noise and makes the results available via a simple TTL-level (3.3V with 5V-tolerant pins) serial interface at baud rates up to 115,200 bps. A USB-to-serial adapter can be used to connect the IMU to a computer running the free IMUkit PC application, which can be used for data visualization and settings configuration.

Update: Units are now being shipped with firmware version 2.0, which adds an on-board Extended Kalman Filter (EKF) for automatic pitch and roll angle estimation.

Note that the board’s pins are spaced 2 mm apart, so the board will not work with standard 0.1" headers or breadboards.

Product Comparison

We carry several inertial measurement and orientation sensors. The table below compares their capabilities:

Product Name	Sensors			Estimation				Other
Product Name	Gyros (3x)	Accels (3x)	Mag (3x)	Roll	Pitch	Yaw	Quaternion	Enclosure
Pololu MinIMU-9
CHR-6d IMU *
CHR-UM6-LT Orientation Sensor
CHR-UM6 Orientation Sensor

* Discontinued.

Features

On-board EKF for pitch and roll angle estimation (firmware version 2.0+ only)
3 gyro axes and 3 accelerometer axes
±400°/s gyro range
±3 g accelerometer range

Data output rate adjustable from 20 to 300 Hz
Weighs under 1.5 grams (0.05 oz)
Small size: 20 x 18 x 3 mm (0.8" x 0.7" x 0.1")
Configurable windowed Parks-McClellan FIR filter
TTL UART communication interface (3.3V with 5V-tolerant pins) can stream data or provide data on request
16-bit angle outputs provide 0.01° resolution
Cortex firmware and PC application can be customized

Open Source PC Application and Firmware

Both the PC application for communicating with the CHR-6d and the CHR-6d’s firmware are open source and available for download from the Resources tab. All of the pins needed to reprogram the STM32F103T8 ARM Cortex processor are made available to the user, as are four unused digital I/O pins that can be put to use if the firmware is modified.