How to send and receive CAN FD Frames with more than 8 Bytes of data.

[abauske]

Title states the problem. We can only send and receive data using

bool CAN0_MessageTransmitFifo(uint8_t numberOfMessage, CAN_TX_BUFFER *txBuffer);
or
bool CAN0_MessageReceiveFifo(CAN_RX_FIFO_NUM rxFifoNum, uint8_t numberOfMessage, CAN_RX_BUFFER *rxBuffer);

respectively. However in https://github.com/Microchip-MPLAB-Harmony/csp/blob/f6814f5b3f60f7743dad711b866c929169dc0037/peripheral/can_u2003/templates/plib_can_common.h.ftl#L370C3-L370C3 it is hardcoded that both rx and tx buffer objects only contain a maximum of 8 data bytes.

More drastically in https://github.com/Microchip-MPLAB-Harmony/csp/blob/f6814f5b3f60f7743dad711b866c929169dc0037/peripheral/can_u2003/templates/plib_can.c.ftl#L238C14-L238C14 we copy data from register buffer to rx buffer object. Let's assume in MCC we configured FiFo size to hold the maximum of 64 Data Bytes (there is a dropdown for that for Rx and Tx Fifos in MCC). In that case MCC declares macro #define CAN0_RX_FIFO0_ELEMENT_SIZE 72U (which sounds reasonable for 4 Byte Id + 4 Bytes Misc + 64 Bytes Data; too lazy to check with datasheet, as this is not the point I am making) which means we copy 72 Bytes of data in a struct that is only 16 Bytes of size, causing overflow and therefore undefined behaviour.

Possible ways forward:

• Increase data length to constant 64 Bytes --> wastes memory for all of us that only want to use 8 Byte maximum, but easily implemented
• Configure data length according to user selection in MCC --> probably most elegant solution

Keep in mind I might have overlook some consequences.