Ben Pololu IMU

Ben Pololu IMU is an experiment with the Ben NanoNote and the MinIMU-9 Gyro, Accelerometer, and Compass (L3G4200D and LSM303DLM Carrier) board from Pololu.

Goals

• Experiment with I2C communication using the 8:10 port (see UBB)
• Evaluate the accuracy of digital gyroscope and accelerometer components
• Consider applications of orientation and positioning data
• Refresh mostly dormant vector mathematics knowledge

Progress

The MinIMU-9, with the supplied male headers attached, can be conveniently connected to female headers soldered to the Sparkfun microSD Sniffer: as is the case with the 8:10 pin ordering, the VIN and GND pins are adjacent on the MinIMU-9, and thus the connection can be built around them without the need for jumper wires. The board is quite able to function on power supplied by the Ben.

Communication with the board is done using the I²C protocol which requires only two additional wires from the 8:10 port. Although Linux kernel support could probably be employed to conduct I²C communication using the GPIO lines associated with the 8:10 interface, a user space implementation is currently being used, with threading involved to reduce latency between measurements.

A repository is available containing code to allow the Ben to communicate with the IMU, and some results are shown below.

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  The unlabelled underside of the MinIMU-9 with protruding header pins (with the soldering having been done on the labelled side of the board)

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  The MinIMU-9 connected to a Sparkfun microSD sniffer (in correct orientation for insertion into the 8:10 port)

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  The MinIMU-9 connected to the Ben in a horizontal position, showing the orientation information from the board

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  The MinIMU-9 connected to the Ben in a vertical position, showing the orientation information from the board (and with the acceleration indicator producing a small reading)

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  Dynamic display of orientation information from the MinIMU-9 on the Ben's screen