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How to remap CAN-Pins for a STM32F042 TSSOP20 Chip

DRied
Associate II

Hi,

I'm going to use a STM32F042F6P in TSSOP20 - case for a application using CAN - connectivity. The low-pin-version of the STM32F042 demand to remap the CAN-pins to alternate pins.

I already discovered the hint for bit 4 (PA11_PA12_RMP) of SYSCFG_CFGR1 for repmapping PA11/PA12 to PA9/PA10 (pin 17/18 of the TSSOP20 chip), but unfortunately it simply doesn't work.

I checked my firmware with a LQFP32 type of the chip (NUCLEO-Board) with CAN - pins on PA11/PA12 - so everything seams to work properly. My idea was simply to change SYSCFG_CFGR1.4 - bit for the smaller case chip and have fun with the stuff.

Please can anybody tell me weather there is anything else to do transfer my CAN-Program from STM32F042K4U (LQFP32) to STM32F042F6P (TSSOP20), or is the remap-bit the only neccessary changing?

My second question is, does pin-remapping work with GPIOs to? As a test, I tried to remap PA11/PA12 to PA9/PA10 and to toggle PA11/PA12 then, but this didn't run too.

Thanks a lot for your help.

5 REPLIES 5

Don't you need to do the PA11/PA12 vs PA9/PA10 switch, and then set the AF4 for PA11/PA12 pin configuration?

https://www.st.com/resource/en/datasheet/stm32f042f6.pdf

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      /* Enable GPIO TX/RX clock */
      __HAL_RCC_SYSCFG_CLK_ENABLE();
      __HAL_RCC_GPIOA_CLK_ENABLE();
 
      __HAL_REMAP_PIN_ENABLE(HAL_REMAP_PA11_PA12); // SYSCFG_CFGR1_PA11_PA12_RMP
 
      /* Enable CAN clock */
      __HAL_RCC_CAN1_CLK_ENABLE();
 
      /*##-2- Configure peripheral GPIO ##########################################*/
      /* UART TX GPIO pin configuration  */
      GPIO_InitStruct.Pin       = GPIO_PIN_11 | GPIO_PIN_12;
      GPIO_InitStruct.Mode      = GPIO_MODE_AF_PP;
      GPIO_InitStruct.Pull      = GPIO_NOPULL;
      GPIO_InitStruct.Speed     = GPIO_SPEED_FREQ_HIGH;
      GPIO_InitStruct.Alternate = GPIO_AF4_CAN;
 
      HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
 
...
 sourcer32@gmail.com

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DRied
Associate II

Hello Clive,

thank you very much for your prompt reply.

I use the MIKROE C compiler, and they offer a routine for CAN - Setup including bit timing, pin setup etc. There AF4 configuration is done. With the LQFP - type it worked well.

But do you know whether one step is to be done before the other, or is that not important?

Kraal
Senior III

Hi there,

Did you notice that Clive's example first enabled the clock for the SYSCFG ? Are you also enabling the clock for SYSCFG before changing bit 4 in SYSCFG_CFGR1 ?

DRied
Associate II

Good morning Clive and Kraal,

thank you very much for your help again.

With your advice I was able to fix the problem.

I myself would never have come up with the idea of searching this corner for the cause of the error.

You were therefore a great help - thank you again.