CAN-SPI-CAN MCP251863 Click

[jguico]

Hi,

I'm working on a project that involves sending CAN signals from a PC, communicating with a microcontroller using SPI, and relaying signals back to the PC using CAN. This is a feedback loop that involves going from CAN, to SPI, and then back to CAN.

I purchased the MCP251863 Click with the understanding that the IC has a CAN transceiver and controller that would allow me to communicate with MCUs even if they don't support the CAN interface. So first, I wanted to confirm that the first half of the feedback loop was possible, where the CAN signals are transmitted from the PC, and the microcontroller was receiving SPI.

I have an external CAN module that I'm using to send signals to the IC through the CAN H/L bus lines. The module has a console that I can use to modify the bits in the signal. This is the CAN module: https://www.inno-maker.com/product/usb2can-cable/

I am also using an external SPI module connected to SCK, SDI, GND, and CS. The module also has a console that I can use to the modify the bits in the signal. This is the SPI module: https://www.totalphase.com/products/aardvark-i2cspi/

I am also providing both 3.3V and 5V to the corresponding pins, and I have the STBY/ON jumper set to the ON position.

When only sending SPI signals into the SDI pin, probing the SDO pin with an oscilloscope confirms that we are getting our expected SPI output. However, there is no observable signal at the CAN H/L lines. Similarly, when sending only CAN signals to the CAN bus lines, the SDO pin has no output. Finally, when sending SPI and CAN signals simultaneously, neither signal's bitstreams are affected by the other's.

Question: Are these signals supposed to be independent of each other?
If so, how would I be able to confirm that signals I'm sending in CAN are actually being received by an MCU in SPI?

My thinking was that one signal's bitstream would affect the other's bitstream since the CAN controller is the interface between the MCU and transceiver.
I don't currently have an MCU to test with, so I was wondering if this is even possible to confirm without an MCU.