APM32 CAN总线离线

问题描述：CAN总线离线后无法再次上线
CAN配置代码如下：

void CAN_Config_Init(void)
{
    RCM_EnableAPB1PeriphClock(RCM_APB1_PERIPH_CAN);

    CAN_Config_T       canConfig;
    CAN_FilterConfig_T FilterStruct;

    CAN_Reset();//复位

    CAN_ConfigStructInit(&canConfig);

    /* CAN init */
    canConfig.autoBusOffManage = DISABLE;
    canConfig.autoWakeUpMode   = DISABLE;
    canConfig.nonAutoRetran    = DISABLE;
    canConfig.rxFIFOLockMode   = DISABLE;
    canConfig.txFIFOPriority   = ENABLE;
    canConfig.mode             = CAN_MODE_NORMAL;
    canConfig.syncJumpWidth    = CAN_SJW_1;
	//配置波特率 125kbps
    canConfig.timeSegment1     = CAN_TIME_SEGMENT1_4;
    canConfig.timeSegment2     = CAN_TIME_SEGMENT2_3;
    canConfig.prescaler = 48;	
    CAN_Config(&canConfig);
    FilterStruct.filterNumber = CAN_FILTER_NUMBER_1;
    FilterStruct.filterMode = CAN_FILTER_MODE_IDMASK;
    FilterStruct.filterScale = CAN_FILTER_SCALE_32BIT;
    FilterStruct.filterIdHigh = (uint16_t)((u32RevCan_Id0>>13)&0xffff);
    FilterStruct.filterIdLow  = ((uint16_t)u32RevCan_Id0<<3&0xffff)|CAN_TYPEID_EXT;
    FilterStruct.filterMaskIdHigh = 0xffff;
    FilterStruct.filterMaskIdLow  = 0x0000;
    FilterStruct.filterFIFO = CAN_FIFO_0;
    FilterStruct.filterActivation =  ENABLE;
	CAN_ConfigFilter(&FilterStruct);	
	FilterStruct.filterNumber = CAN_FILTER_NUMBER_0;
    FilterStruct.filterMode = CAN_FILTER_MODE_IDMASK;
    FilterStruct.filterScale = CAN_FILTER_SCALE_32BIT;
    FilterStruct.filterIdHigh = (uint16_t)((u32RevCan_Id1>>13)&0xffff);
    FilterStruct.filterIdLow  = ((uint16_t)u32RevCan_Id1<<3&0xffff)|CAN_TYPEID_EXT;
    FilterStruct.filterMaskIdHigh = 0xffff;
    FilterStruct.filterMaskIdLow  = 0x0000;
    FilterStruct.filterFIFO = CAN_FIFO_0;
    FilterStruct.filterActivation =  ENABLE;
    CAN_ConfigFilter(&FilterStruct);	
	CAN_EnableInterrupt(CAN_INT_F0MP);//使能中断 FIFO 0 message pending Interrupt
}

查看代码无果，跑个调试，发现掉线后发送程序总会进入到发送邮箱满的标志中，这就导致无法发送数据。

这个时候就往CAN模块出错这个方向上查找问题。查询手册中的出错管理：

从手册中的描述中我们可以发现，发送出错会导致CAN总线控制器离线，离线之后不能接收和发送报文。
调试模式下，查看相应的标志位，此时发现发送错误计数就会一直增加，最后导致离线。

此时就可以得出结论：设备离线的原因就是发送错误计数超过了255，导致了CAN总线控制器离线，无法再次发送CAN报文。
手册中也提到了离线恢复的机制：

查询离线标志位BOFLG，当检测到离线后，重新初始化CAN即可重新上线。

if(BOFLG==1)//如果检测到CAN控制器离线
{
 CAN_init();//执行一遍初始化代码
}