在使用DMA做RS485通信的时候，需要在发送的时候将芯片设置为发送，在发送完毕设置为接收模式。但是用下面的代码，程序一直在发送的函数里面死循环，无法理解，下面是我的代码，请做过的朋友帮我分析一下谢谢！
时钟使能了的
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1 , ENABLE);
中断向量也是打开了的
/* Enable DMA1 channel2 IRQ Channel RS485发送完成中断 */
NVIC_InitStructure.NVIC_IRQChannel = DMA1_Channel2_IRQChannel;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
GPIO也是设置好的
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9 | GPIO_Pin_10 | GPIO_Pin_13 | GPIO_Pin_15; //CAN TX(PB9),RS485 TX(PA9),SPI SCK(PB13),SPI MOSI(PB15)设置为复用功能推挽输出
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_Init(GPIOB, &GPIO_InitStructure);
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_11; //RS485 RX(PB11) 设置为输入浮空
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
GPIO_Init(GPIOB, &GPIO_InitStructure);
/********************************************************************************
*函数原型: void RS232_Init(u32 baud)
*参数说明: baud: 波特率
*返回值: 无
*说明: USART 通讯口初始化程序 设置帧格式: 8 个数据位,无奇偶效验位,1个停止位 8N1
*
0：2400 bps 4.2MS 每字节
1：9600bps 1MS 每字节
2：19200bps 0.5MS 每字节
3：38400bps 0.25 每字节
4：115200bps 0.087MS 每字节
* 对于通信接收数据打包的判断，一个就是接收数据超过64字节，另外就是超时的计算，超时
* 设定为各个通信波特率的，两字节传输时间没有收到数据就打包发出。
********************************************************************************/
void RS485Bus_Init(u8 BaudNum) //USART 通讯口初始化程序
{
USART_InitTypeDef USART_InitStructure;
DMA_InitTypeDef DMA_InitStructure;
u32 baud = 19200;
switch(BaudNum)
{
case 0: baud = 2400;
break;
case 1: baud = 9600;
break;
case 2: baud = 19200;
break;
case 3: baud = 38400;
break;
case 4: baud = 115200;
break;
default : baud = 19200;
break;
}
USART_InitStructure.USART_BaudRate = baud; //波特率设置
USART_InitStructure.USART_WordLength = USART_WordLength_8b; //通讯格式 8N1,无硬件流控
USART_InitStructure.USART_StopBits = USART_StopBits_1;
USART_InitStructure.USART_Parity = USART_Parity_No;
USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;
USART_Init(USART3, &USART_InitStructure);
///////////////////////////////////首先开启一次DMA传送使DMA1_FLAG_TC2 置位/////////////////////
DMA_DeInit(DMA1_Channel2);
DMA_InitStructure.DMA_PeripheralBaseAddr = USART3_DR_Base;
DMA_InitStructure.DMA_MemoryBaseAddr = (u32)RS485BusTxData;
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
DMA_InitStructure.DMA_BufferSize = 1;
DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;
DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;
DMA_InitStructure.DMA_Priority = DMA_Priority_VeryHigh;
DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
DMA_Init(DMA1_Channel2, &DMA_InitStructure);
DMA_ClearFlag(DMA1_FLAG_TC2);
DMA_ITConfig(DMA1_Channel2, DMA_IT_TC, ENABLE); //使能发送完成中断
/* DMA1 Channel3 (triggered by USART3_RX event) Config */
DMA_DeInit(DMA1_Channel3);
DMA_InitStructure.DMA_PeripheralBaseAddr = USART3_DR_Base;
DMA_InitStructure.DMA_MemoryBaseAddr = (u32)RS485BusRxData;
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
DMA_InitStructure.DMA_BufferSize = RS485_BUF_NUM;
DMA_Init(DMA1_Channel3, &DMA_InitStructure);
USART_DMACmd(USART3, USART_DMAReq_Rx | USART_DMAReq_Tx, ENABLE);
USART_ITConfig(USART3, USART_IT_IDLE, ENABLE); //接收空闲中断使能
DMA_Cmd(DMA1_Channel2, ENABLE);
DMA_Cmd(DMA1_Channel3, ENABLE);
USART_Cmd(USART3, ENABLE);
}
/********************************************************************************
*函数原型: void RS232_SendData(void)
*参数说明: Len : 帧数据长度
* *data : 指向发送数据寄存器组
*返回值: 无
*说明: 将待发送的数据发送出去
********************************************************************************/
void RS485Bus_SendData(void) //将待发送的数据发送出去
{
DMA_InitTypeDef DMA_InitStructure;
RS485_TXEN; //发送使能
while (DMA_GetFlagStatus(DMA1_FLAG_TC2) == RESET); //等待上一个数据帧发送完毕
DMA_DeInit(DMA1_Channel2);
DMA_InitStructure.DMA_PeripheralBaseAddr = USART3_DR_Base;
DMA_InitStructure.DMA_MemoryBaseAddr = (u32)RS485BusTxData;
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
DMA_InitStructure.DMA_BufferSize = RS485BusTxNum;
DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;
DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;
DMA_InitStructure.DMA_Priority = DMA_Priority_VeryHigh;
DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
DMA_Init(DMA1_Channel2, &DMA_InitStructure);
DMA_ClearFlag(DMA1_FLAG_TC2);
DMA_ITConfig(DMA1_Channel2, DMA_IT_TC, ENABLE); //使能发送完成中断
DMA_Cmd(DMA1_Channel2, ENABLE);
}
发送完成中断函数，清标记，设置RS485为接收状态
void DMA1_Channel2_IRQHandler(void)
{
//DMA1 Channel2 发送完成中断 */
if(DMA_GetITStatus(DMA1_IT_TC2) != RESET)
{
DMA_ClearITPendingBit(DMA1_IT_TC2); //清中断标志
RS485_RXEN; //接收使能
}
}
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