STM32 使用DMA接收485设备数据问题

jungle1989 · 发表于 2019-3-26 22:26:49

使用STM32 DMA传输+空闲中断，实现任意长度数据接收，接收到从机设备发来的数据，始终第一个字节多一个0x00。各位大神，帮忙分析一下啊！ QQ截图20190326222455.png

void USART1_IRQHandler(void)
{
uint8_t len = 0;
BaseType_t xHigherPriorityTaskWoken;

if(USART_GetITStatus(USART1,USART_IT_IDLE) != RESET) //
{
USART_ClearITPendingBit(USART1, USART_IT_IDLE);

len = USART1->SR;
            len = USART1->DR;

DMA_Cmd(DMA2_Stream5,DISABLE);//1Ø±Õ½óêÕDMA
DMA_ClearFlag(DMA2_Stream5,DMA_FLAG_TCIF5);//Çå3yDMA′«êä±êÖ¾
len = Usart1_BufferSize - DMA_GetCurrDataCounter(DMA2_Stream5);//»ñè¡½óêÕÖ¡3¤
Usart1_RxLength = len;
if(len > 0)
{
//·￠Ëíò»¸öDÅoÅá¿1yè￥￡¬¾í¿éòÔ′|àíêy¾YáË
if(Usart1RxSemaphore != NULL)//DÅoÅá¿óDD§
{
xSemaphoreGiveFromISR(Usart1RxSemaphore,&xHigherPriorityTaskWoken);//êí·Å¶tÖμDÅoÅá¿
portYIELD_FROM_ISR(xHigherPriorityTaskWoken);
}
}
DMA_SetCurrDataCounter(DMA2_Stream5,Usart1_BufferSize);//éèÖÃêy¾Y′«êä3¤¶è
DMA_Cmd(DMA2_Stream5,ENABLE);//′ò¿aDMA
}
if(USART_GetITStatus(USART1, USART_IT_PE | USART_IT_FE | USART_IT_NE) != RESET)//3ö′í
{
      USART_ClearITPendingBit(USART1, USART_IT_PE | USART_IT_FE | USART_IT_NE);
}
}