# CAN Problems with MCP2515, MCP2561 and Rpi

I work with some devices which used STM32 MCU and MCP2561. Theses devices talks on a CAN Bus. Everything is ok.

But when i plug a Raspberry Pi with a MCP2515(Spi) and a MCP2561. I see a lot of invalid frames on my scope like this :

A valid CAN Frame is like :

A zoom on the problem :

I don't understand why there is a problem at the ACK/ACK Delimiter.

• In your 'valid' frame, the ACK slot does not look right either. Why is it only at 2V? I assume you measure not only one line (CANH) but the difference between CANH and CANL, correct? What else is connected to the bus besides the scope? Do you have termination resistor(s) in place? – JimmyB Jun 21 '19 at 13:17