Pi 4 with CAN Bus and UPS HATs


I purchased a 2-Channel Isolated CAN Expansion HAT and have ran through the steps in Waveshare Wiki with success. I then added a UPS which uses pogo pins to attach to the Pi, it uses pins:
2: 5v
3: GPIO 02
5: GPIO 03
9: GND
I have a warning at start up: Failed to load overlay 'spi-bcm2835-overlay'

when I re attach the can bus hat and run dmesg | grep spi I receive this reply

[    10.389055] mcp251x spi0.0: MCP251x didn't enter in conf mode after reset
[    10.389160] mcp251x spi0.0: Probe failed, err=110
[    10.389171] mcp251x probe of spi0.0 failed with error -110
[    10.571099] mcp251x spi0.1 can0: MCP2515 successfully initiliazed.

If I turn the Pi off, turn the UPS off, re power the Pi from its own power port, I still receive the overlay warning at start up, however when I run dmesg | grep spi I receive a successful return. So it appears the UPS and 2ch hat are sharing pins.

my end goal for this pi, is that it will be setup on the centre of the dash in my car, reading the CAN Bus of the ECU, and the idea behind the UPS is that when ign power goes off, the Pi will go to standby mode instead of turning off each time.

Any ideas how I can get these working together?

Hi Daniel, Welcome to the Forums!!!

It looks like some other people have had similar issues when using other CAN interfaces on the Pi.

Having a look at the documentation for both the CAN HATS and UPS it looks like the only shared pin is a ground. so It doesn’t look like its a hardware issue at the moment.

I’d recommend having a look though this thread on the topic from some other users with the same issue.

I hope this helps get you on your way with your project.