The hardware I’m using here is a Raspberry Pi Type A, described in detail here. My previous post (Part 1: Modules and Packages) configured the Raspberry Pi to use the I2C connection. The aim in this post is to connect to a SparkFun 9DOF Sensor Stick (SEN-10724) which has a 3-axis accelerometer (ADXL345), a 3-axis gyro (ITG-3200) and a 3-axis compass / magnetometer (HMC5883L) all sharing an I2C interface.
Raspberry Pi Type A connected via I2C with a SparkFun 9DOF Sensor Stick (SEN-10724)
There are three separate devices on the sensor stick all hooked up to the same I2C bus. You can see the addresses listed below. The HMC5883L compass / magnetometer uses address 1e. The ADXL345 accelerometer uses address 53. The ITG-3200 gyroscope uses address 68. (The ‘UU’ at address 3b indicates an address reserved by the kernel, but I don’t know for what.)
~ $ sudo i2cdetect -y 1
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- 1e --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- UU -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- 53 -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- 68 -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
2. Connecting to the Sensor Stick
I’m not the first to use this stick, and there is, for example, a project by Peter Bartz which uses the stick:
Attitude and Heading Reference System (AHRS). More useful, perhaps, is Rolfe Schmidt’s muCSense work with it here and here.
All three I2C devices have open source (MIT license) C++ device libraries available from I2Cdevlib:
These rely on the underlying Wire class written for the Arduino, however, so a Raspberry Pi implementation of the Wire class is necessary (and one or two other miscellaneous functions).
I am currently working on this – find the latest source here, and a discussion topic here.