I made my first usable board in the reflow oven today. It is a board I designed about 6 months ago and never built out. It is a dual CAN data logger, using a dsPIC33 to do the dual CAN bus messaging, and a Raspberry PI Zero W daughter card to do the logging to SD card, network connection, auto download, etc.

I originally used a MCP2515 connected to the PI directly over SPI, but the 2515 doesn’t have a FIFO so at high data rates it would drop packets. I could have used the new MCP2517FD, but I would need two of them to do 2 CAN busses, and while they have FIFOs, it would still require PI interactions for bus to bus transfers.

By having the dsPIC33 onboard talking to the PI over SPI I can have the configuration information stored on the PI, but the bus-to-bus interactions can happen all on the dsPIC in realtime with no risk of any latency. This will be helpful for cases where I want to MITM a CAN device.

I need to work on the software, but a few quick code bits tested the dsPIC33 and the PI with GPIO comms and CAN initialization. I need to design the protocol I’ll use for the dsPIC33 to PI SPI communications, then write that driver.

It was great to pull the board out of the oven, double check some things, and power it right up!