Questions about G474 FDCAN

[wang_mo_mo]

The FDCAN loopback test of G474 can enter the receive interrupt, but normally the two devices communicate with each other, and when one of the devices is used to debug, it is found that the interrupt cannot be entered。

[SofLit]

Hello @wang_mo_mo ,

The question is not clear but the loopback mode is intended to be used for a standalone configuration (the node is the receiver and the sender at the same time) not used to connect two nodes.

[wang_mo_mo]

II certainly know that loopback mode "FDCAN_MODE_INTERNAL_LOOPBACK" is on a chip that uses the Tx pin to send data to the Rx pin. I used a chip loopback test that was successful, but the two machines were "FDCAN_MODE_NORMAL" in normal mode and could not transfer data to each other

Well, let me put it another way, if I succeed in the loopback test, does it prove that my software configuration is fine?

[SofLit]

Ok. Now it is clear. You succeeded with Loopback mode and not with Normal mode.

It could due to:

- Something related to your connections.

- Something related to the HW including the transceivers you are using.

- An issue with the bitrate / Clock source you have used.

But for that we need more details about your HW configuration, your schematics .. Your code.

"if I succeed in the loopback test, does it prove that my software configuration is fine?"

--> partially yes. but for example, if your bitrate configuration is not correct you can succeed with loopback mode but not in normal mode because the bitrate is not the same in both nodes.

[wang_mo_mo · Accepted solution]

Hello comrade, the test was successful, as shown in the picture, originally I chose "FD mode with BitRate Switching".

Changing to FD mode without BitRate Switching can output data normally, which should not be wrong, but in the experiment, changing to "FD mode with BitRate Switching" will not output CAN packets. It's weird, I don't know why, let's study it later, let's leave it at that.

Well, I'm not going to upload images, anyway you should be able to understand what I mean.