RT-Thread-RT-Thread CAN驱动无法通讯的问题与解决RT-Thread问答社区

RT-Thread CAN驱动无法通讯的问题与解决

发布于 2022-08-15 10:41:33 浏览：1236 订阅该版

[tocm]

近几天在调试RT的CAN，发现了一些问题，会导致CAN通讯异常，整理了一下分享给大家

## 1、针对于APB1总线为42M的时钟配置，会导致波特率异常
会有这样一种情况，比如使用了F429的芯片，但是外部配了个8M XTAL,所以过了锁相环之后一般是168M的sys_clock，这样会导致APB1总线为42M，而RT在做CAN的波特率的时候针对于APB1时钟42M和45M的配置是不一样的。
如下图
```c
#if defined(STM32F405xx) || defined(STM32F415xx) || defined(STM32F407xx)|| defined(STM32F417xx) ||\
    defined(STM32F401xC) || defined(STM32F401xE) || 1 /* 42MHz(max) */
static const struct stm32_baud_rate_tab can_baud_rate_tab[] =
{
    {CAN1MBaud, (CAN_SJW_2TQ | CAN_BS1_9TQ  | CAN_BS2_4TQ | 3)},
    {CAN800kBaud, (CAN_SJW_2TQ | CAN_BS1_8TQ  | CAN_BS2_5TQ | 4)},
    {CAN500kBaud, (CAN_SJW_2TQ | CAN_BS1_9TQ  | CAN_BS2_4TQ | 6)},
    {CAN250kBaud, (CAN_SJW_2TQ | CAN_BS1_9TQ  | CAN_BS2_5TQ | 12)},
    {CAN125kBaud, (CAN_SJW_2TQ | CAN_BS1_9TQ  | CAN_BS2_5TQ | 24)},
    {CAN100kBaud, (CAN_SJW_2TQ | CAN_BS1_9TQ  | CAN_BS2_5TQ | 30)},
    {CAN50kBaud, (CAN_SJW_2TQ | CAN_BS1_9TQ  | CAN_BS2_5TQ | 60)},
    {CAN20kBaud, (CAN_SJW_2TQ | CAN_BS1_9TQ  | CAN_BS2_5TQ | 150)},
    {CAN10kBaud, (CAN_SJW_2TQ | CAN_BS1_9TQ  | CAN_BS2_5TQ | 300)}
};
#else  /* APB1 45MHz(max) */
static const struct stm32_baud_rate_tab can_baud_rate_tab[] =
{
    {CAN1MBaud, (CAN_SJW_2TQ | CAN_BS1_9TQ  | CAN_BS2_5TQ | 3)},
    {CAN800kBaud, (CAN_SJW_2TQ | CAN_BS1_8TQ  | CAN_BS2_5TQ | 4)},
    {CAN500kBaud, (CAN_SJW_2TQ | CAN_BS1_9TQ  | CAN_BS2_5TQ | 6)},
    {CAN250kBaud, (CAN_SJW_2TQ | CAN_BS1_9TQ  | CAN_BS2_5TQ | 12)},
    {CAN125kBaud, (CAN_SJW_2TQ | CAN_BS1_9TQ  | CAN_BS2_5TQ | 24)},
    {CAN100kBaud, (CAN_SJW_2TQ | CAN_BS1_9TQ  | CAN_BS2_5TQ | 30)},
    {CAN50kBaud, (CAN_SJW_2TQ | CAN_BS1_9TQ  | CAN_BS2_5TQ | 60)},
    {CAN20kBaud, (CAN_SJW_2TQ | CAN_BS1_9TQ  | CAN_BS2_5TQ | 150)},
    {CAN10kBaud, (CAN_SJW_2TQ | CAN_BS1_9TQ  | CAN_BS2_5TQ | 300)}
};
#endif
```
当然原来RT的42M的时钟配置不是这样的，（官方给的42M的时钟配置和45M的是完全一样的，我的RT是4.0.3）以上代码是改过后的42M的时钟配置
## 2、RT的CAN设备的使用会导致当前线程会被阻塞，CAN设备有时也会被阻塞
该问题主要是由于drv_can.c里的底层的错误状态导致进入无效循坏。当然这个问题在论坛里好多大神进行过讨论，亲测注释掉错误标志是最为有限的方法，其余的包括开启自动重发等等，皆试过，没有任何用，改后的代码在下方，仅供参考
```c
static int _can_sendmsg(struct rt_can_device *can, const void *buf, rt_uint32_t box_num)
{
    CAN_HandleTypeDef *hcan;
    hcan = &((struct stm32_can *) can->parent.user_data)->CanHandle;
    struct rt_can_msg *pmsg = (struct rt_can_msg *) buf;
    CAN_TxHeaderTypeDef txheader = {0};
    HAL_CAN_StateTypeDef state = hcan->State;

/* Check the parameters */
    RT_ASSERT(IS_CAN_DLC(pmsg->len));

if ((state == HAL_CAN_STATE_READY) ||
            (state == HAL_CAN_STATE_LISTENING))
    {
        /*check select mailbox  is empty */
        switch (1 << box_num)
        {
        case CAN_TX_MAILBOX0:
            if (HAL_IS_BIT_SET(hcan->Instance->TSR, CAN_TSR_TME0) != SET)
            {
                /* Change CAN state */
//                hcan->State = HAL_CAN_STATE_ERROR;
                /* Return function status */
                return -RT_ERROR;
            }
            break;
        case CAN_TX_MAILBOX1:
            if (HAL_IS_BIT_SET(hcan->Instance->TSR, CAN_TSR_TME1) != SET)
            {
                /* Change CAN state */
//                hcan->State = HAL_CAN_STATE_ERROR;
                /* Return function status */
                return -RT_ERROR;
            }
            break;
        case CAN_TX_MAILBOX2:
            if (HAL_IS_BIT_SET(hcan->Instance->TSR, CAN_TSR_TME2) != SET)
            {
                /* Change CAN state */
//                hcan->State = HAL_CAN_STATE_ERROR;
                /* Return function status */
                return -RT_ERROR;
            }
            break;
        default:
            RT_ASSERT(0);
            break;
        }

if (RT_CAN_STDID == pmsg->ide)
        {
            txheader.IDE = CAN_ID_STD;
            RT_ASSERT(IS_CAN_STDID(pmsg->id));
            txheader.StdId = pmsg->id;
        }
        else
        {
            txheader.IDE = CAN_ID_EXT;
            RT_ASSERT(IS_CAN_EXTID(pmsg->id));
            txheader.ExtId = pmsg->id;
        }

if (RT_CAN_DTR == pmsg->rtr)
        {
            txheader.RTR = CAN_RTR_DATA;
        }
        else
        {
            txheader.RTR = CAN_RTR_REMOTE;
        }
        /* clear TIR */
        hcan->Instance->sTxMailBox[box_num].TIR &= CAN_TI0R_TXRQ;
        /* Set up the Id */
        if (RT_CAN_STDID == pmsg->ide)
        {
            hcan->Instance->sTxMailBox[box_num].TIR |= (txheader.StdId << CAN_TI0R_STID_Pos) | txheader.RTR;
        }
        else
        {
            hcan->Instance->sTxMailBox[box_num].TIR |= (txheader.ExtId << CAN_TI0R_EXID_Pos) | txheader.IDE | txheader.RTR;
        }
        /* Set up the DLC */
        hcan->Instance->sTxMailBox[box_num].TDTR = pmsg->len & 0x0FU;
        /* Set up the data field */
        WRITE_REG(hcan->Instance->sTxMailBox[box_num].TDHR,
                  ((uint32_t)pmsg->data[7] << CAN_TDH0R_DATA7_Pos) |
                  ((uint32_t)pmsg->data[6] << CAN_TDH0R_DATA6_Pos) |
                  ((uint32_t)pmsg->data[5] << CAN_TDH0R_DATA5_Pos) |
                  ((uint32_t)pmsg->data[4] << CAN_TDH0R_DATA4_Pos));
        WRITE_REG(hcan->Instance->sTxMailBox[box_num].TDLR,
                  ((uint32_t)pmsg->data[3] << CAN_TDL0R_DATA3_Pos) |
                  ((uint32_t)pmsg->data[2] << CAN_TDL0R_DATA2_Pos) |
                  ((uint32_t)pmsg->data[1] << CAN_TDL0R_DATA1_Pos) |
                  ((uint32_t)pmsg->data[0] << CAN_TDL0R_DATA0_Pos));
        /* Request transmission */
        SET_BIT(hcan->Instance->sTxMailBox[box_num].TIR, CAN_TI0R_TXRQ);

return RT_EOK;
    }
    else
    {
        /* Update error code */
        hcan->ErrorCode |= HAL_CAN_ERROR_NOT_INITIALIZED;

return -RT_ERROR;
    }
}
```