One of the boards that I've been working on over the last couple of months is an updated Pixie IMU / flight controller. In the previous iteration I put very little I/O on the main board, intending to make a few I/O boards for various configurations. On this iteration I reverted back to a more traditional design, which includes many communications options as well as an expansion port for connecting peripheral boards.
Version 0.96 of the Pixie board includes the following:
Version 0.96 of the Pixie board includes the following:
- 24x24 mm board, with 20 mm hole spacing
- 2 grams
- STM32F415RG MCU
- MPU-9250 IMU (via SPI)
- MS5611-01BA03 Pressure Sensor (via SPI)
- MX25L3206E 32 Mb SPI Flash
- USB OTG
- 10-pin servo port, supporting 8 output(/input) channels
- USART1 port
- USART3/I2C port
- USART2 port with flow control. Also supports 4 ADC. Can also serve as a combination Voltage / Current / Sonar / Rx input port.
- CAN port with 3.3V transceiver
- 12 pin (dual 0.05") expansion header, supporting SPI2, UART6, and SWD. Also contains CAN2 (without transceiver).
- Expansion header outputs both battery/USB voltage and 3.3V (up to 500mA total current).
Pixie Version 0.96 - top of board
Above you can see the top of the board, containing the MCU, IMU, pressure senser, and flash. The expansion header (yes it's misspelled on the board) can be seen on the left.
Pixie V0.96 - bottom of board
Above you can see the bottom of the board. It's pretty crowded with connectors, but most of the components fit on the top of the board, so it's not too crowded. The bottom includes the voltage regulator and CAN transceiver.
Pixie compared to (prototype) OpenPilot Revolution
In the picture above you can see a size comparison between the Pixie and a an OpenPilot Revolution board, which is 35x35 mm.
So far I've been able to load a version of a TauLabs bootloader and firmware and verify that the MPU-9250 and SPI flash work as expected. Unfortunately the board has a minor defect that destroyed the chip select line on the pressure sensor, so I'm currently unable to test that. I still need to test the CAN interface and all the I/O ports.
For some reason the magnetometer is flaky on the MPU-9250. Sometimes it is detected and sometimes not. I suspect the MPU-9250 is just bad, but I need to replace it to know for sure. It's been re-flowed a couple of times, so it might be just heat damaged.
As soon as I have the firmware fully configured I plan to flight test it. I have a couple of options for mounting it, as I'll go over in a future post.
So far I've been able to load a version of a TauLabs bootloader and firmware and verify that the MPU-9250 and SPI flash work as expected. Unfortunately the board has a minor defect that destroyed the chip select line on the pressure sensor, so I'm currently unable to test that. I still need to test the CAN interface and all the I/O ports.
For some reason the magnetometer is flaky on the MPU-9250. Sometimes it is detected and sometimes not. I suspect the MPU-9250 is just bad, but I need to replace it to know for sure. It's been re-flowed a couple of times, so it might be just heat damaged.
As soon as I have the firmware fully configured I plan to flight test it. I have a couple of options for mounting it, as I'll go over in a future post.
Pixie V0.96 Schematic
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