轉自http://www.lxway.com/4095951911.htm
前言:開始學USART+DMA的時候看到帖子《STM32 UART DMA實現未知數據長度接收》,覺得方法妙極了。此下出自此帖子——(整體的思路是這樣的,一開始設置好DMA接收,可以把緩衝區長度設置爲幀最大長度,我們可以把RX連接到定時器的管腳輸入端,並且一開始設置輸入並且使能引腳下降沿中斷,當幀的第一個字節發送時,因爲起始位爲低電平,空閒時UART爲高電平,滿足條件,進入中斷,禁止中斷,並且在中斷中開啓定時器,該定時器工作在復位模式,上升沿復位,並且設置好定時器輸出比較值爲超時時間,比如20ms,這樣,在傳輸後面字節時,肯定會有高低電平出現,即便是傳輸的是0x00,0xFF,雖然UART數據區不變,但是都爲1,或都爲0,但是因爲起始位爲低電平,停止位是高電平,所以肯定會有上升沿,定時器會一直復位,輸出定時器的計數器一直到達不了輸出比較值,當一幀傳輸結束後,定時在最後一個字節復位後,由於沒有數據繼續到達,無法復位,則計數器就能計到輸出比較值,這時發出中斷,在定時器中斷中可以計算出接收數據的長度,並且通知外部數據已經接收完畢。)
今天我在工作中調通了另一種USART+DMA接收未知數據長度的接收,使用的是USRAT空閒總線中斷接收,這種方法也在網站上比較多見,以前沒試過,今天才知道如此的爽,另外我使用DMA發送USART數據替代了以前的查詢法發送,發現更加爽了。其速度快了很多,尤其是在大量數據傳輸與發送的時候其優勢更加明顯。
我舉個例子:1、後臺數據->USART1-> USART2->其它設備,其它設備數據->USART2-> USART1->後臺,這兩個數據過程也可能同時進行。
2、由於硬件的限制,USART1和USART2的傳輸波特率不一樣,比如USART1使用GPRS通信,USART2使用短距離無線通信;或者USART1使用以太網通信,USART2使用485總線通信。
由於在寢室只有筆記本電腦,只有一個串口轉USB,沒辦法實現兩個串口之間的數據轉發了,只好實現串口各自的數據轉發。
現在我把我實現的過程簡單描述一下:
1、 初始化設置:USART1_RX+DMA1_ Channel5,USART2_RX+DMA1_ Channel6,USART1_TX+DMA1_ Channel4,USART2_TX+DMA1_ Channel7(具體設置請看程序包)。
2、 當數據發送給USART1接收完畢時候會引起USART1的串口總線中斷,計算DMA1_ Channel5內存數組剩餘容量,得到接收的字符長度。將接收的字符給DMA1_ Channel4內存數組,啓動DMA1_ Channel4通道傳輸數據,(傳輸完成需要關閉。)下一次數據接收可以在啓動DMA1_ Channel4時候就開始,不需要等待DMA1_ Channel4數據傳輸完成。但是上一次DMA1_ Channel4完成之前,不可以將數據給DMA1_ Channel4內存數組,會沖掉以前數據。
3、 USART2類同USART1。
,下面貼程序:IO口定義:
void GPIO_Configuration(void)
{
GPIO_InitTypeDef GPIO_InitStructure;
/* 第1步:打開GPIO和USART部件的時鐘 */
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_AFIO, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);
/* 第2步:將USART Tx的GPIO配置爲推輓複用模式 */
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOA, &GPIO_InitStructure);
/* 第3步:將USART Rx的GPIO配置爲浮空輸入模式
由於CPU復位後,GPIO缺省都是浮空輸入模式,因此下面這個步驟不是必須的
但是,我還是建議加上便於閱讀,並且防止其它地方修改了這個口線的設置參數
*/
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
GPIO_Init(GPIOA, &GPIO_InitStructure);
/* 第1步:打開GPIO和USART2部件的時鐘 */
//RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_AFIO, ENABLE);
RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2, ENABLE);
/* 第2步:將USART2 Tx的GPIO配置爲推輓複用模式 */
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOA, &GPIO_InitStructure);
/* 第3步:將USART2 Rx的GPIO配置爲浮空輸入模式
由於CPU復位後,GPIO缺省都是浮空輸入模式,因此下面這個步驟不是必須的
但是,我還是建議加上便於閱讀,並且防止其它地方修改了這個口線的設置參數
*/
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_3;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
GPIO_Init(GPIOA, &GPIO_InitStructure);
/*第3步已經做了,因此這步可以不做
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
*/
GPIO_Init(GPIOA, &GPIO_InitStructure);
}
串口初始化:
void USART_Configuration(void)
{
USART_InitTypeDef USART_InitStructure;
/* 第4步:配置USART參數
- BaudRate = 115200 baud
- Word Length = 8 Bits
- One Stop Bit
- No parity
- Hardware flow control disabled (RTS and CTS signals)
- Receive and transmit enabled
*/
USART_InitStructure.USART_BaudRate = 19200;
USART_InitStructure.USART_WordLength = USART_WordLength_8b;
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(USART1, &USART_InitStructure);
//空閒中斷
USART_ITConfig(USART1, USART_IT_IDLE , ENABLE);
/* 第5步:使能 USART, 配置完畢 */
USART_Cmd(USART1, ENABLE);
/* CPU的小缺陷:串口配置好,如果直接Send,則第1個字節發送不出去
如下語句解決第1個字節無法正確發送出去的問題 */
USART_ClearFlag(USART1, USART_FLAG_TC); /* 清發送外城標誌,Transmission Complete flag */
USART_InitStructure.USART_BaudRate = 9600;
USART_InitStructure.USART_WordLength = USART_WordLength_8b;
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(USART2, &USART_InitStructure);
USART_ITConfig(USART2, USART_IT_IDLE , ENABLE);//開啓空閒,幀錯,噪聲,校驗錯中斷
USART_Cmd(USART2, ENABLE);
/* CPU的小缺陷:串口配置好,如果直接Send,則第1個字節發送不出去
如下語句解決第1個字節無法正確發送出去的問題 */
USART_ClearFlag(USART2, USART_FLAG_TC); /* 清發送外城標誌,Transmission Complete flag */
}
DMA配置:
void DMA_Configuration(void)
{
DMA_InitTypeDef DMA_InitStructure;
/* DMA clock enable */
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);//DMA1
/* DMA1 Channel4 (triggered by USART1 Tx event) Config */
DMA_DeInit(DMA1_Channel4);
DMA_InitStructure.DMA_PeripheralBaseAddr = 0x40013804;
DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)USART1_SEND_DATA;
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
DMA_InitStructure.DMA_BufferSize = 512;
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_Circular;
DMA_InitStructure.DMA_Priority = DMA_Priority_High;
DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
DMA_Init(DMA1_Channel4, &DMA_InitStructure);
DMA_ITConfig(DMA1_Channel4, DMA_IT_TC, ENABLE);
DMA_ITConfig(DMA1_Channel4, DMA_IT_TE, ENABLE);
/* Enable USART1 DMA TX request */
USART_DMACmd(USART1, USART_DMAReq_Tx, ENABLE);
DMA_Cmd(DMA1_Channel4, DISABLE);
/* DMA1 Channel5 (triggered by USART2 Tx event) Config */
DMA_DeInit(DMA1_Channel7);
DMA_InitStructure.DMA_PeripheralBaseAddr = 0x40004404;
DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)USART2_SEND_DATA;
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
DMA_InitStructure.DMA_BufferSize = 512;
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_Circular;
DMA_InitStructure.DMA_Priority = DMA_Priority_High;
DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
DMA_Init(DMA1_Channel7, &DMA_InitStructure);
DMA_ITConfig(DMA1_Channel7, DMA_IT_TC, ENABLE);
DMA_ITConfig(DMA1_Channel7, DMA_IT_TE, ENABLE);
/* Enable USART1 DMA TX request */
USART_DMACmd(USART2, USART_DMAReq_Tx, ENABLE);
DMA_Cmd(DMA1_Channel7, DISABLE);
/* DMA1 Channel5 (triggered by USART1 Rx event) Config */
DMA_DeInit(DMA1_Channel5);
DMA_InitStructure.DMA_PeripheralBaseAddr = 0x40013804;
DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)USART1_RECEIVE_DATA;
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
DMA_InitStructure.DMA_BufferSize = 512;
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_Circular;
DMA_InitStructure.DMA_Priority = DMA_Priority_High;
DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
DMA_Init(DMA1_Channel5, &DMA_InitStructure);
DMA_ITConfig(DMA1_Channel5, DMA_IT_TC, ENABLE);
DMA_ITConfig(DMA1_Channel5, DMA_IT_TE, ENABLE);
/* Enable USART1 DMA RX request */
USART_DMACmd(USART1, USART_DMAReq_Rx, ENABLE);
DMA_Cmd(DMA1_Channel5, ENABLE);
/* DMA1 Channel6 (triggered by USART1 Rx event) Config */
DMA_DeInit(DMA1_Channel6);
DMA_InitStructure.DMA_PeripheralBaseAddr = 0x40004404;
DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)USART2_RECEIVE_DATA;
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
DMA_InitStructure.DMA_BufferSize = 512;
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_Circular;
DMA_InitStructure.DMA_Priority = DMA_Priority_Medium;
DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
DMA_Init(DMA1_Channel6, &DMA_InitStructure);
DMA_ITConfig(DMA1_Channel6, DMA_IT_TC, ENABLE);
DMA_ITConfig(DMA1_Channel6, DMA_IT_TE, ENABLE);
/* Enable USART2 DMA RX request */
USART_DMACmd(USART2, USART_DMAReq_Rx, ENABLE);
DMA_Cmd(DMA1_Channel6, ENABLE);
}
中斷優先級配置:
void NVIC_Configuration(void)
{
NVIC_InitTypeDef NVIC_InitStructure;
/* Configure one bit for preemption priority */
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);
/* Enable the USART1 Interrupt */
NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 2;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
/* Enable the USART2 Interrupt */
NVIC_InitStructure.NVIC_IRQChannel = USART2_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 2;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 2;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
//Enable DMA Channel4 Interrupt
NVIC_InitStructure.NVIC_IRQChannel = DMA1_Channel4_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
//Enable DMA Channel7 Interrupt
NVIC_InitStructure.NVIC_IRQChannel = DMA1_Channel7_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 2;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
/*Enable DMA Channel5 Interrupt */
NVIC_InitStructure.NVIC_IRQChannel = DMA1_Channel5_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 2;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
/*Enable DMA Channel6 Interrupt */
NVIC_InitStructure.NVIC_IRQChannel = DMA1_Channel6_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 2;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
}
數組定義,含義如題名:
u8 USART1_SEND_DATA;
u8 USART2_SEND_DATA;
u8 USART1_RECEIVE_DATA;
u8 USART2_RECEIVE_DATA;
u8 USART1_TX_Finish=1;// USART1發送完成標誌量
u8 USART2_TX_Finish=1; // USART2發送完成標誌量
USART1中斷服務函數
void USART1_IRQHandler(void)
{
u16 DATA_LEN;
u16 i;
if(USART_GetITStatus(USART1, USART_IT_IDLE) != RESET)//如果爲空閒總線中斷
{
DMA_Cmd(DMA1_Channel5, DISABLE);//關閉DMA,防止處理其間有數據
//USART_RX_STA = USART1->SR;//先讀SR,然後讀DR才能清除
//USART_RX_STA = USART1->DR;
DATA_LEN=512-DMA_GetCurrDataCounter(DMA1_Channel5);
if(DATA_LEN > 0)
{
while(USART1_TX_Finish==0)//等待數據傳輸完成才下一次
{
;
}
//將數據送DMA存儲地址
for(i=0;i<DATA_LEN;i++)
{
USART1_SEND_DATA=USART1_RECEIVE_DATA;
}
//USART用DMA傳輸替代查詢方式發送,克服被高優先級中斷而產生丟幀現象。
DMA_Cmd(DMA1_Channel4, DISABLE); //改變datasize前先要禁止通道工作
DMA1_Channel4->CNDTR=DATA_LEN; //DMA1,傳輸數據量
USART1_TX_Finish=0;//DMA傳輸開始標誌量
DMA_Cmd(DMA1_Channel4, ENABLE);
}
//DMA_Cmd(DMA1_Channel5, DISABLE);//關閉DMA,防止處理其間有數據
DMA_ClearFlag(DMA1_FLAG_GL5 | DMA1_FLAG_TC5 | DMA1_FLAG_TE5 | DMA1_FLAG_HT5);//清標誌
DMA1_Channel5->CNDTR = 512;//重裝填
DMA_Cmd(DMA1_Channel5, ENABLE);//處理完,重開DMA
//讀SR後讀DR清除Idle
i = USART1->SR;
i = USART1->DR;
}
if(USART_GetITStatus(USART1, USART_IT_PE | USART_IT_FE | USART_IT_NE) != RESET)//出錯
{
USART_ClearITPendingBit(USART1, USART_IT_PE | USART_IT_FE | USART_IT_NE);
}
USART_ClearITPendingBit(USART1, USART_IT_TC);
USART_ClearITPendingBit(USART1, USART_IT_IDLE);
}
USART2中斷服務函數
void USART2_IRQHandler(void)
{
u16 DATA_LEN;
u16 i;
if(USART_GetITStatus(USART2, USART_IT_IDLE) != RESET) //如果爲空閒總線中斷
{
DMA_Cmd(DMA1_Channel6, DISABLE);//關閉DMA,防止處理其間有數據
//USART_RX_STA = USART1->SR;//先讀SR,然後讀DR才能清除
//USART_RX_STA = USART1->DR;
DATA_LEN=512-DMA_GetCurrDataCounter(DMA1_Channel6);
if(DATA_LEN > 0)
{
while(USART2_TX_Finish==0)//等待數據完成才下一次
{
;
}
//將數據送DMA存儲地址
for(i=0;i<DATA_LEN;i++)
{
USART2_SEND_DATA=USART2_RECEIVE_DATA;
}
//USART用DMA傳輸替代查詢方式發送,克服被高優先級中斷而產生丟幀現象。
DMA_Cmd(DMA1_Channel7, DISABLE); //改變datasize前先要禁止通道工作
DMA1_Channel7->CNDTR=DATA_LEN; //DMA1,傳輸數據量
USART2_TX_Finish=0;//DMA傳輸開始標誌量
DMA_Cmd(DMA1_Channel7, ENABLE);
}
//DMA_Cmd(DMA1_Channel5, DISABLE);//關閉DMA,防止處理其間有數據
DMA_ClearFlag(DMA1_FLAG_GL6 | DMA1_FLAG_TC6 | DMA1_FLAG_TE6 | DMA1_FLAG_HT6);//清標誌
DMA1_Channel6->CNDTR = 512;//重裝填
DMA_Cmd(DMA1_Channel6, ENABLE);//處理完,重開DMA
//讀SR後讀DR清除Idle
i = USART2->SR;
i = USART2->DR;
}
if(USART_GetITStatus(USART2, USART_IT_PE | USART_IT_FE | USART_IT_NE) != RESET)//出錯
{
USART_ClearITPendingBit(USART2, USART_IT_PE | USART_IT_FE | USART_IT_NE);
}
USART_ClearITPendingBit(USART2, USART_IT_TC);
USART_ClearITPendingBit(USART2, USART_IT_IDLE);
}
DMA1_Channel5中斷服務函數
void DMA1_Channel5_IRQHandler(void)
{
DMA_ClearITPendingBit(DMA1_IT_TC5);
DMA_ClearITPendingBit(DMA1_IT_TE5);
DMA_Cmd(DMA1_Channel5, DISABLE);//關閉DMA,防止處理其間有數據
DMA1_Channel5->CNDTR = 580;//重裝填
DMA_Cmd(DMA1_Channel5, ENABLE);//處理完,重開DMA
}
DMA1_Channel6中斷服務函數
void DMA1_Channel6_IRQHandler(void)
{
DMA_ClearITPendingBit(DMA1_IT_TC6);
DMA_ClearITPendingBit(DMA1_IT_TE6);
DMA_Cmd(DMA1_Channel6, DISABLE);//關閉DMA,防止處理其間有數據
DMA1_Channel6->CNDTR = 580;//重裝填
DMA_Cmd(DMA1_Channel6, ENABLE);//處理完,重開DMA
}
DMA1_Channel4中斷服務函數
//USART1使用DMA發數據中斷服務程序
void DMA1_Channel4_IRQHandler(void)
{
DMA_ClearITPendingBit(DMA1_IT_TC4);
DMA_ClearITPendingBit(DMA1_IT_TE4);
DMA_Cmd(DMA1_Channel4, DISABLE);//關閉DMA
USART1_TX_Finish=1;//置DMA傳輸完成
}
DMA1_Channel7中斷服務函數
//USART2使用DMA發數據中斷服務程序
void DMA1_Channel7_IRQHandler(void)
{
DMA_ClearITPendingBit(DMA1_IT_TC7);
DMA_ClearITPendingBit(DMA1_IT_TE7);
DMA_Cmd(DMA1_Channel7, DISABLE);//關閉DMA
USART2_TX_Finish=1;//置DMA傳輸完成
},全部完,但是程序在開始啓動時會出現自己發幾個不知道什麼字符,之後一切正常。如有什麼問題,請大神指教。個人認爲問題不大,因爲在工作的時候通過STM32訪問後臺或者後臺訪問STM32大量的間隔密的數據時沒有出現問題。而如果沒有使用DMA,單幀數據發收可以,多幀數據經過USART1轉USART2,就收不到從USART2反饋的第二幀數據了。不一定是速度上的問題,可能是我處理順序的問題,但是不管是巧合,還是瞎撞的,總歸解決辦法的就是好辦法。