After using our I/O boards for over a year, we had a series of changes we wanted to make in order to improve reliability and simplify integration with the CPU board and other on-board electronics.
Particular issues we needed to address included:
Since we have been happy with the performance of the u-blox NEO-7N, we decided to integrate that directly; we also moved the HMC5883L magnetometer onto the board, and added an MS4525DO I2C differential pressure sensor for the pitot tubes. Although those components require quite a bit of board space, replacing the large number of external connectors with a single 30-pin latching connector meant that the boards didn’t need to be much bigger than the previous revision.
The new boards exhibit very similar sensor performance to the old boards in static tests, however performance of the GPS is markedly improved by the extra supply rail filtering we’ve added to the design. In addition, the pitot sensor is a much higher-quality part (1.5% total error band) than we have been using, so we expect in-flight AHRS performance to be considerably better.
The latest I/O monitor source code, including AVR32 drivers for the Invensense MPU6000 (SPI), Measurement Specialties MS4525DO and MS5611 (I2C), the Honeywell HMC5883L (I2C) and the u-blox NEO-7N (TTL serial) is available at sfwa/iomon.