CAN filter API not correctly implemented for STM32F0 (and possibly other STM32)

[martinjaeger]

Description

• Type: Bug
• Priority: Minor

Target
STM32F0 and possibly other STM32 family MCUs

The function int can_filter(can_t *obj, uint32_t id, uint32_t mask, CANFormat format, int32_t handle) in can_api.c is not correctly implemented for STM32F0.

Current implementation:

    sFilterConfig.FilterIdHigh = (uint8_t) (id >> 8);
    sFilterConfig.FilterIdLow = (uint8_t) id;
    sFilterConfig.FilterMaskIdHigh = (uint8_t) (mask >> 8);
    sFilterConfig.FilterMaskIdLow = (uint8_t) mask;

does not set the filter according to actual register layout described in Reference Manual RM0091 (page 832).

Fixed implementation of entire function

int can_filter(can_t *obj, uint32_t id, uint32_t mask, CANFormat format, int32_t handle) 
{
    int retval = 0;

    // filter for CANAny format cannot be configured for STM32
    if((format == CANStandard) || (format == CANExtended)) {

        CanHandle.Instance = (CAN_TypeDef *)(obj->can);
        CAN_FilterConfTypeDef  sFilterConfig;

        sFilterConfig.FilterNumber = handle;
        sFilterConfig.FilterMode = CAN_FILTERMODE_IDMASK;
        sFilterConfig.FilterScale = CAN_FILTERSCALE_32BIT;

        if(format == CANStandard) {
            sFilterConfig.FilterIdHigh = id << 5;
            sFilterConfig.FilterIdLow =  0x0;
            sFilterConfig.FilterMaskIdHigh = mask << 5;
            sFilterConfig.FilterMaskIdLow = 0x0;    // allows both remote and data frames
        }
        else if(format == CANExtended){
            sFilterConfig.FilterIdHigh = id >> 13;  // EXTID[28:13]
            sFilterConfig.FilterIdLow = (0x00FF & (id << 3)) | (1 << 2);  // EXTID[12:0]
            sFilterConfig.FilterMaskIdHigh = mask >> 13;
            sFilterConfig.FilterMaskIdLow = (0x00FF & (mask << 3)) | (1 << 2);
        }

        sFilterConfig.FilterFIFOAssignment = 0;
        sFilterConfig.FilterActivation = ENABLE;
        sFilterConfig.BankNumber = 14 + handle;

        HAL_CAN_ConfigFilter(&CanHandle, &sFilterConfig);   
        retval = handle;
    }
    return retval;
}

The fixed function was successfully tested with STM32F072 Nucleo board, using extended and standard format.

[bcostm]

This issue is fixed now and can be closed.