CAN interface Difference between STM32F103R8 (64pin) and STM32F103T8 (36pin)

[MRisu]

Hello there

Because I have less space on a new PCB and don't need all of the I/Os I want to take the smaller STMF103T8. As far as I know its the same silicium with less pins. So I can take the same software with some adjustments in the HAL.

With the R8 the CAN interface was remapped on PB8/PB9. The T8 has the CAN interface only on PA11/PA12. So I tested the CAN interface on my original R8 with the PA11/PA12 and it worked perfectly. But for some reason it doesn't work with the T8.

I don't find any posibilities anymore, so I hope you can help me.

Here are my port configurations for the CAN interface which works with the R8 but doesn't work with the T8:

  RCC->APB2ENR |= 0x00000004;   // enable port A

AFIO->MAPR  &= 0xFFFF9FFF;   // clear bits 14:13 (CAN1_REMAP)

  GPIOA->CRH  &= 0xFFF0FFFF;   // clear PA12 configuration

  GPIOA->CRH  |= 0x00090000;   // PA12: alternate function push-pull (2MHz)

I've also seen, that the T8 has some restrictions with timer1 if you use the CAN interface. But I'm using timer4.

[MRisu]

No ideas or is it a difficult description?

[Tesla DeLorean]

It's a 10+ year old part design, and I don't care?

For F1's pay attention to what else is mapped to those pins and remap that off somewhere else, off into the void if necessary. Check the errata. Check a decade of posting on related topics.

Have you enabled the AFIO clock to allow remapping to work?

[MRisu]

Yeah AFIO clock is enabled, otherwise it wouldn't works with the 64pin R8...

it must has a difference between the two controllers what influence the CAN interface.