Hello,
Using nucleo-H723ZG board: to use CAN with this board you have either:
- Use FDCAN in loopback mode not in normal mode (which is your current config). The CAN cannot be handled as UART or SPI it has same specificity like arbitration, error management etc.. this arbitration is done when at least two nodes are connected via CAN bus through transceivers (normal mode).
In loopback mode, this arbitration mode is managed internally in the cell. so Rx and Tx pins are connected internally in the chip. refer to RM0468 rev2 page 2524/2524: External and internal loop back modes
For loopback mode example, please refer to the example provided under: \Projects\STM32H743I-EVAL\Examples\FDCAN\FDCAN_Loopback
- Use FDCAN in normal mode but you have to add an external transceiver to connect your board to another CAN node through CAN bus (differential mode). You can use For example FDCAN2/FDCAN3 in normal mode but you have to add a transceiver for each one.
But at the same time you have to select the correct transceiver: classic mode which reaches 1Mb/s and FDCAN: it depends on what bitrates you will use.
For the clock, for loopback mode you may not encounter communication issues, but in normal mode you will. So for your design you have to an external precise crystal. For example you can use the clock source provided by ST-Link (8MHz) in bypass mode.
STM32
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