G431pin-multiplexing-in-fdcan1: in Different GPIO Port

[HL_Efeng]

As addicated in DataSheet and CubeMX, there are two FDCAN1_Tx and two FDCAN1_RX in STM32G431CBT6. In my Prj, I used PA12 for Tx and PB8-BOOT0 for Rx, and my chip can only work in FDCAN_MODE_Ext._Loopback, and without any receive func be implemented. After I changed the FDCAN pin from PA12&PB8 to PB9&PB8 and adjusted my wire routing, the problem has be handled. so If the STM32G4 can use FDCAN pin from different port in some case? If not. I think it should be fixed in CubeMX, because CubeMX allows users to select CAN pin from different ports without any warning.​

[mƎALLEm]

Hello @HL_Efeng and welcome to the ST community,

The problem is not clear. You need to elaborate more..

In which case is not working: Normal mode? Loopback mode? etc .. are you using a CAN tranceiver..

Not possible to help you with the description you've provided.

My preliminary answer: you can use any combination of alternate functions of CAN_Tx/CAN_Rx.

PS: I didn't understand this statements:

"and my chip can only work in FDCAN_MODE_Ext._Loopback, and without any receive func be implemented."

"After I changed the FDCAN pin from PA12&PB8 to PB9&PB8 and adjusted my wire routing, the problem has be handled"

 

 

[HL_Efeng]

Sorry for my unclear description.

My design uses PA12 and PB8 as CAN_Tx and CAN_Rx, and I used a tranceiver correctly. the CAN only work in ExtLoopbackMode(Data can be send out correctly, but can not receive).

in Normal Mode, It works like this performance：When I first call the Func AddTxFifo in my program, the CAN tranceiver will send out an "000" and nothing later, and this 000 is consindered as CAN_ID by my CAN analyser. When I Second or more call it, it will send an "01F" and nothing later, also consindered as CAN_ID.

FDCAN will enter bus_off after 16th call, and no more data be sendout anymore, until I reinit FDCAN or reset my board.

After I edited my design, and uses PB9&PB8 as CAN_Tx and CAN_Rx, It works correctly both in Normal and Loopback mode.

Thankyou for timely reply.

 

[mƎALLEm]

Still not clear.

In Normal mode, did you connect another CAN node to the CAN bus? if not, that couldn't work. You need to establish a complete CAN node where at least two CAN nodes are present on the CAN bus.

Do you have a condition where the Normal mode is working? if yes please describe the environment.

 

[Andrew Neil]

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@HL_Efeng wrote:

 PB8-BOOT0 for Rx

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Do you need to take special measures to disable the BOOT0 function on that pin?

[HL_Efeng]

I used CubeProg to set Boot1bit by software.

[HL_Efeng]

edited my post description.Sorry for my unclear des.

[mƎALLEm]

 In fact, in Ext.LoopbackMode, it can send msg correctly. this has already inferred that the PA12 is correctly connected.

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As PA12 is toggling as expected and the loopback mode works correctly but not in normal mode, that's either a hardware issue: broken transceiver, bad wiring or wrong/bad connections.. VIO pin of the transceiver connected to VDD of STM32? You need to inspect all the CAN bus you have.

Or bit timing issue: (but this is not the case since it works with PB9.

So double check again your hardware ... Probe PA12, probe PB9 with a logic analyzer or an oscilloscope and check the differences.

[mƎALLEm]

 In fact, in Ext.LoopbackMode, it can send msg correctly. this has already inferred that the PA12 is correctly connected.

---

As PA12 is toggling as expected and the loopback mode works correctly but not in normal mode, that's either a hardware issue: broken transceiver, bad wiring or wrong/bad connections.. VIO pin of the transceiver connected to VDD of STM32? You need to inspect all the CAN bus you have.

Or bit timing issue: (but this is not the case since it works with PB9.

So double check again your hardware ... Probe PA12, probe PB9 with a logic analyzer or an oscilloscope and check the differences.

[HL_Efeng]

At this point, it seems it can only be attributed to the bad PCB wiring. maybe the signal integrity has bad enough that STM32 cannot read a bit.

Wait. Maybe PB8 has broken? Maybe PA12 has transmitted a bit, but PB8 had not received. Let me check it by GPIO_Input. I will reply here in some days.

Thankyou for your patience.