FDCAN no ACK

Adam_Stastny · ‎2024-12-12

Hi,

I am trying to use a STM32G491KEU6 with FDCAN, but the communication is failing at line:

if (HAL_FDCAN_AddMessageToTxFifoQ(&hfdcan1, &TxHeader, TxData) != HAL_OK) { ...

I found out that this is a problem that receiver is not sending a ACK bit - cannot it be a software issue? I am using two STM32G491KEU6 with the same code mentioned bellow, while I am also using a TCAN3403DRBRQ1 transceiver on both boards.
The boards seems ok, I can even see a transmittion on the line with oscilloscope, but there is probably no ACK.

Thank you for any help

Adam_Stastny · ‎2024-12-15

Ahh, I found the issue... CAN LOW differential had short circuit to GND - bad soldering. Thank you for your time.

View solution in original post

SofLit · ‎2024-12-12

Hello,

For CAN/FDCAN subject especially when using Normal mode you need to provide more details especially the HW part. So please share schematics.

Also, I recommend to use HSE with an external crystal instead of HSI.

As per your code:

RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;

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Adam_Stastny · ‎2024-12-12

I am sending a schematic. In my PCB, there is also a GND on pin 8 STB (by datasheet, this should allow normal mode instead of standby mode).

Thx for that recommendation.

SofLit · ‎2024-12-12

Hello,

Could you please share your ioc file?

Chenge FrameFormat to FDCAN_FRAME_CLASSIC;

Could you also please state on Y1? could you please share its datasheet?

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Adam_Stastny · ‎2024-12-12

Yeah, no prob.
Y1 should not be the issue - I am using a classic CAN with the same Y1 and STM32F446RET6 and it works as it should.

Datasheet: https://cz.mouser.com/datasheet/2/122/ecx_53b-3074848.pdf

SofLit · ‎2024-12-13

Ok,

But contrary to what I suggested earlier, here you are still using HSI:

And CAN mode :

-> Try to switch to Classic mode.

And also, are you sure the two nodes have the same config especially the bitrate?

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Adam_Stastny · ‎2024-12-13

Yeah,
I am using the same code on both devices so there should be a problem.
Anyway, I fixed what you recommended, but still the issue remains.

MHoll.2 · ‎2024-12-15

Hi

If You are using the TCAN3404-Q1 (from the schematics) You need to set the STB pin to low (internal pullup!)

If You are using the TCAN3403-Q1 (from the first post) then You have to put Pin 5 (Vio) to 3.3V

Martin

Adam_Stastny · ‎2024-12-15

As I mentioned, I already did that on my PCBs with a wire - it did not help.

Adam_Stastny · ‎2024-12-15

Ahh, I found the issue... CAN LOW differential had short circuit to GND - bad soldering. Thank you for your time.