STM32 printf 重定向到CAN

最近在调试一款电机驱动板使用的是CAN总线而且板子上只有一个CAN
想移植Easylogger到上面试试easylogger的效果，先实现pritnf的重定向功能来打印输出
只需要添加以下代码即可实现

代码

#include <stdarg.h>
uint8_t FDCAN_UserTxBuffer[512];
void FDCAN_printf(const char *format, ...)
{
	va_list args;
	uint32_t length;

	va_start(args, format);
	length = vsnprintf((char *)FDCAN_UserTxBuffer, 512, (char *)format, args);
	va_end(args);
    FDCAN_Send_Data(0x100,FDCAN_UserTxBuffer,length);
}

/* CAN 发送一帧数据 */
void FDCAN_Send_Message(uint32_t id, uint8_t *buf, uint8_t len)
{
  FDCAN_TxHeaderTypeDef TxHeader;
  /* 配置Tx缓冲区消息 */
  TxHeader.Identifier = id;                /* 报文ID */
  TxHeader.IdType = FDCAN_EXTENDED_ID;     /* 扩展ID模式  */
  TxHeader.TxFrameType = FDCAN_DATA_FRAME; /* 数据帧 */

#if defined(CLASSIC_CAN)
  if (len >= 8)
    len = 8;
  uint32_t CAN_FRAME_DL = len ;
#else
  uint32_t CAN_FRAME_DL = FDCAN_DLC_BYTES_64; /* FDCAN 默认使用64*/
#endif

  TxHeader.DataLength = CAN_FRAME_DL;              /* 数据帧长度 */
  TxHeader.ErrorStateIndicator = FDCAN_ESI_ACTIVE; /*发送节点错误 */
  TxHeader.BitRateSwitch = FDCAN_BRS_OFF;          /* 无波特率切换 */
  TxHeader.FDFormat = CAN_MODE;                    /* CAN模式*/
  TxHeader.TxEventFifoControl = FDCAN_STORE_TX_EVENTS;
  TxHeader.MessageMarker = 0x01;

  /* 发送缓冲区消息 */
  HAL_FDCAN_AddMessageToTxFifoQ(&hfdcan1, &TxHeader, buf);
  while (HAL_FDCAN_GetTxFifoFreeLevel(&hfdcan1) != 3)
    ; /*等待发送完成*/
}
/* CAN发送多帧数据 */
void FDCAN_Send_Data(uint32_t id, uint8_t *buf, uint32_t len)
{
  uint32_t transmission_times = 0; /* 发送次数 */
  uint32_t remian_bytes = 0;       /* 剩余字节 */
  uint32_t frame_length = 0;       /* 帧长度 */

#if defined(CLASSIC_CAN)
  frame_length = 8;
#else
  frame_length = 64;
#endif

  transmission_times = len / frame_length;
  remian_bytes = len % frame_length;

  int i = 0;
  while (i < transmission_times)
  {
    FDCAN_Send_Message(id, buf + i * frame_length, len);
    i++;
  }
  if (remian_bytes > 0)
  {
    FDCAN_Send_Message(id, buf + transmission_times * frame_length, remian_bytes);
  }
}

定义了一个宏定义来实现log测试和应用的分离

/**
 * @brief 输出日志任务
 * @param argument 
 */
void USER_LOG_Task(void *argument)
{
    for (;;)
    {
        #ifdef USER_LOG_ENABLE
        FDCAN_printf("\n Hellow world!\n");
        #endif
        osDelay(1000);

	
    }
}