1、開發平臺
計算機操作系統:WIN7 64位;
開發環境:Keil MDK 5.14;
MCU:STM32F407ZET6;
STM32F4xx固件庫:STM32F4xx_DSP_StdPeriph_Lib_V1.4.0;
串口調試助手;
2、問題描述
在測試用STM32F4xx芯片的串口USART1以DMA方式進行RS485收發通訊時,出現數據字節丟失的現象,一般丟失1~2個字節。
出現問題時測試的簡單收發機制:使能串口USART1的DMA收發功能,開啓了DMA發送完成中斷和USART1空閒中斷。通過串口調試助手發送N個字節給MCU,當MCU產生USART1空閒中斷時,在USART1空閒中斷服務程序中將DMA接收到的N個字節數據從接收緩存拷貝到發送緩存,準備好數據後,RS485切換爲發送模式,通過啓動一次DMA發送,將N個字節數據原樣回送到串口調試助手。最後,在DMA發送完成中斷服務程序中判斷到有DMA發送完成標誌TCIF7置位時,立即將RS485再次切換爲接收模式。
3、原因分析
在STM32F4xx英文參考手冊(RM0090)中,USART章節的使用DMA發送小節給出瞭如下時序圖:
由圖可見,當DMA將第3個字節Frame 3寫到USART數據寄存器USART_DR時,TX線上纔剛準備出現第2個字節Frame 2的時序,並且DMA發送完成中斷標誌在TX線還未出現第2個字節Frame 2時序時就由硬件置1了,所以,如果軟件中在DMA發送完成中斷服務程序中檢測到DMA TCIF標誌置1後馬上將RS485切換爲接收模式,則後面的字節數據將會丟失。
所以,需要讓數據字節不丟失的話,必須讓所有字節(包括字節的停止位)在TX線上穩定發送完成後,才能將RS485切換爲接收模式。
4、解決方法
如上圖所示,有一個關鍵點是:當所有字節(包括字節的停止位)在TX線上穩定發送完成後,串口發送完成標誌(TC flag)置1。所以,有兩個解決方法:
方法一:用DMA發送完成中斷,不用USART1發送完成中斷。在DMA發送完成中斷服務程序中檢測到有TCIF7置1時,再等待USART1發送完成標誌TC置1,直到USART1發送完成標誌TC置1後,清零USART1發送完成標誌TC,然後再將RS485切換爲接收模式。
方法二:用USART1發送完成中斷,不用DMA發送完成中斷。在USART1中斷服務程序USART1_IRQHandler()中,檢測到有USART1發送完成標誌TC置1時,清零USART1發送完成標誌TC,並且要清零DMA發送完成標誌DMA_FLAG_TCIF7,最好同時清零DMA_FLAG_FEIF7、DMA_FLAG_DMEIF7、DMA_FLAG_TEIF7 、DMA_FLAG_HTIF7,然後再將RS485切換爲接收模式。
5、參考源代碼
Usart.h頭文件
/*----------------------------------------------------------------------------------------------------
*Copyright: SXD Tech. Co., Ltd.
*開發 環境: Keil MDK 5.14 && STM32F407ZET6
*文件 名稱: USART串行通信驅動頭文件
*作 者: 順信德
*版 本: V1.0
*日 期: 2018-2-6
*說 明:
*修改 日誌: (1)
----------------------------------------------------------------------------------------------------*/
#ifndef _USART_H_
#define _USART_H_
#include "Global.h"
/*---------------------------------------------宏定義(S)---------------------------------------------*/
#define RS485_Recv(); {PFout(11)=0;} //SP485接收模式,低電平有效
#define RS485_Send(); {PFout(11)=1;} //SP485發送模式,高電平有效
#define USART1_SEND_MAXLEN 512 /*串口1最大發送字節長度*/
#define USART1_RECV_MAXLEN 512 /*串口1最大接收字節長度*/
/*---------------------------------------------宏定義(E)---------------------------------------------*/
/*--------------------------------------------端口定義(S)--------------------------------------------*/
/*--------------------------------------------端口定義(E)--------------------------------------------*/
/*--------------------------------------------變量聲明(S)--------------------------------------------*/
extern u32 G_u32RS485BaudRate; //RS485通訊波特率
extern u8 G_u8Usart1SendBuf[USART1_SEND_MAXLEN]; //發送數據緩衝區
extern u8 G_u8Usart1RecvBuf[USART1_RECV_MAXLEN]; //接收數據緩衝區
extern u16 G_u16CommRecvLen; //通訊接收的一幀數據長度
/*--------------------------------------------變量聲明(E)--------------------------------------------*/
/*--------------------------------------------函數聲明(S)--------------------------------------------*/
extern void USART1_Init(u32 baud); //USART1串口初始化
extern void USART_DMA_SendStart(DMA_Stream_TypeDef *DMA_Streamx, u16 m_u16SendCnt); //串口USART1啓動一次DMA傳輸
extern void USART1_DMA_SendNByte(u8 *m_pSendBuf, u16 m_u16SendCnt); //串口USART1以DMA方式發送多字節
/*--------------------------------------------函數聲明(E)--------------------------------------------*/
#endif
Usart.c源文件方法一:用DMA發送完成中斷
/*----------------------------------------------------------------------------------------------------
*Copyright: SXD Tech. Co., Ltd.
*開發 環境: Keil MDK 5.14 && STM32F407ZET6
*文件 名稱: USART串行通信驅動源文件
*作 者: 順信德
*版 本: V1.0
*日 期: 2018-2-6
*說 明:
*修改 日誌: (1)
----------------------------------------------------------------------------------------------------*/
#include "Usart.h"
/*--------------------------------------------變量定義(S)--------------------------------------------*/
u32 G_u32RS485BaudRate = 9600; //RS485通訊波特率
u8 G_u8Usart1SendBuf[USART1_SEND_MAXLEN]={0,}; //發送數據緩衝區
u8 G_u8Usart1RecvBuf[USART1_RECV_MAXLEN]={0,}; //接收數據緩衝區
u16 G_u16CommRecvLen=0; //通訊接收的一幀數據長度
/*--------------------------------------------變量定義(E)--------------------------------------------*/
/*--------------------------------------------函數聲明(S)--------------------------------------------*/
void USART1_Init(u32 baud); //USART1串口初始化
void USART_DMA_SendStart(DMA_Stream_TypeDef *DMA_Streamx, u16 m_u16SendCnt); //串口USART1啓動一次DMA傳輸
void USART1_DMA_SendNByte(u8 *m_pSendBuf, u16 m_u16SendCnt); //串口USART1以DMA方式發送多字節
/*--------------------------------------------函數聲明(E)--------------------------------------------*/
/*----------------------------------------------------------------------------------------------------
*函數名稱:void USART1_Init(u32 baud)
*函數功能:USART1串口初始化函數
*入口參數:u32 baud - 波特率(單位bps)
*出口參數:無
*說 明:用於RS485通信;
----------------------------------------------------------------------------------------------------*/
void USART1_Init(u32 baud)
{
GPIO_InitTypeDef GPIO_InitStructure;
USART_InitTypeDef USART_InitStructure;
NVIC_InitTypeDef NVIC_InitStructure;
DMA_InitTypeDef DMA_InitStructure;
u16 mid_u16RetryCnt = 0;
USART_DeInit(USART1);
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE); //使能GPIOA時鐘
RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE); //使能USART1時鐘
//USART1對應引腳複用映射
GPIO_PinAFConfig(GPIOA, GPIO_PinSource9, GPIO_AF_USART1); //GPIOA9複用爲USART1_TX
GPIO_PinAFConfig(GPIOA, GPIO_PinSource10, GPIO_AF_USART1); //GPIOA10複用爲USART1_RX
//USART1端口配置
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9 | GPIO_Pin_10; //GPIOA9與GPIOA10
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF; //複用功能
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_25MHz; //速度25MHz
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP; //推輓輸出
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP; //上拉
GPIO_Init(GPIOA, &GPIO_InitStructure); //初始化PA9,PA10
//USART1初始化設置
USART_InitStructure.USART_BaudRate = baud; //波特率設置
USART_InitStructure.USART_WordLength = USART_WordLength_8b; //字長爲8位數據格式
USART_InitStructure.USART_StopBits = USART_StopBits_1; //一個停止位
USART_InitStructure.USART_Parity = USART_Parity_No; //無奇偶校驗位
USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None; //無硬件數據流控制
USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx; //收發模式
USART_Init(USART1, &USART_InitStructure); //初始化USART1
USART_Cmd(USART1, ENABLE); //使能USART1
USART_ClearFlag(USART1, USART_FLAG_TC); //清除發送完成標誌
while(USART_GetFlagStatus(USART1, USART_FLAG_TC) == RESET); //等待空閒幀發送完成後再清零發送完成標誌
USART_ClearFlag(USART1, USART_FLAG_TC); //清除發送完成標誌
USART_ITConfig(USART1, USART_IT_TC, DISABLE); //禁止USART1傳輸完成中斷
USART_ITConfig(USART1, USART_IT_RXNE, DISABLE); //禁止USART1接收不爲空中斷
USART_ITConfig(USART1, USART_IT_TXE, DISABLE); //禁止USART1發送空中斷
USART_ITConfig(USART1, USART_IT_IDLE, ENABLE); //開啓USART1空閒中斷
//USART1 NVIC配置
NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn; //串口1中斷通道
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=3; //搶佔優先級3
NVIC_InitStructure.NVIC_IRQChannelSubPriority =3; //子優先級3
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; //IRQ通道使能
NVIC_Init(&NVIC_InitStructure);
USART_DMACmd(USART1, USART_DMAReq_Tx, ENABLE); //使能串口1的DMA發送
USART_DMACmd(USART1, USART_DMAReq_Rx, ENABLE); //使能串口1的DMA接收
// - USART1發送DMA配置
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA2,ENABLE); //DMA2時鐘使能
DMA_DeInit(DMA2_Stream7);
while ((DMA_GetCmdStatus(DMA2_Stream7) != DISABLE) && (mid_u16RetryCnt++ < 500)); //等待DMA可配置
//配置DMA2_Stream7
DMA_InitStructure.DMA_Channel = DMA_Channel_4; //通道選擇
DMA_InitStructure.DMA_PeripheralBaseAddr = (u32)&USART1->DR; //DMA外設地址
DMA_InitStructure.DMA_Memory0BaseAddr = (u32)G_u8Usart1SendBuf; //DMA 存儲器0地址
DMA_InitStructure.DMA_DIR = DMA_DIR_MemoryToPeripheral; //存儲器到外設模式
DMA_InitStructure.DMA_BufferSize = USART1_SEND_MAXLEN; //數據傳輸量
DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable; //外設非增量模式
DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable; //存儲器增量模式
DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte; //外設數據長度:8位
DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte; //存儲器數據長度:8位
DMA_InitStructure.DMA_Mode = DMA_Mode_Normal; //使用普通模式
DMA_InitStructure.DMA_Priority = DMA_Priority_Medium; //中等優先級
DMA_InitStructure.DMA_FIFOMode = DMA_FIFOMode_Disable;
DMA_InitStructure.DMA_FIFOThreshold = DMA_FIFOThreshold_Full;
DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single; //存儲器突發單次傳輸
DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single; //外設突發單次傳輸
DMA_Init(DMA2_Stream7, &DMA_InitStructure); //初始化DMA Stream
//DMA2_Stream7的NVIC配置
NVIC_InitStructure.NVIC_IRQChannel = DMA2_Stream7_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
DMA_ClearITPendingBit(DMA2_Stream7, DMA_IT_TCIF7); //清除DMA發送完成中斷標誌
DMA_ITConfig(DMA2_Stream7, DMA_IT_TC, ENABLE); //使能DMA發送完成中斷
DMA_Cmd(DMA2_Stream7, ENABLE); //使能DMA2_Stream7
// - USART1接收DMA配置
mid_u16RetryCnt = 0;
DMA_DeInit(DMA2_Stream5);
while ((DMA_GetCmdStatus(DMA2_Stream5) != DISABLE) && (mid_u16RetryCnt++ < 500)); //等待DMA可配置
//配置DMA2_Stream5
DMA_InitStructure.DMA_Channel = DMA_Channel_4; //通道選擇
DMA_InitStructure.DMA_PeripheralBaseAddr = (u32)&USART1->DR; //DMA外設地址
DMA_InitStructure.DMA_Memory0BaseAddr = (u32)G_u8Usart1RecvBuf; //DMA 存儲器0地址
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralToMemory; //外設到存儲器模式
DMA_InitStructure.DMA_BufferSize = USART1_RECV_MAXLEN; //數據傳輸量
DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable; //外設非增量模式
DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable; //存儲器增量模式
DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte; //外設數據長度:8位
DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte; //存儲器數據長度:8位
DMA_InitStructure.DMA_Mode = DMA_Mode_Normal; //使用普通模式
DMA_InitStructure.DMA_Priority = DMA_Priority_Medium; //中等優先級
DMA_InitStructure.DMA_FIFOMode = DMA_FIFOMode_Disable;
DMA_InitStructure.DMA_FIFOThreshold = DMA_FIFOThreshold_Full;
DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single; //存儲器突發單次傳輸
DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single; //外設突發單次傳輸
DMA_Init(DMA2_Stream5, &DMA_InitStructure); //初始化DMA Stream
DMA_Cmd(DMA2_Stream5, ENABLE); //使能DMA2_Stream5
}
/*--------------------------------------------------------------------------------------
函數名稱:void USART_DMA_SendStart(DMA_Stream_TypeDef *DMA_Streamx, u16 m_u16SendCnt)
函數功能:串口USART1啓動一次DMA傳輸函數
入口參數:DMA_Stream_TypeDef DMA_Streamx - DMA數據流(DMA1_Stream0~7/DMA2_Stream0~7);
u16 m_u16SendCnt - 待傳輸數據字節數
出口參數:無
說 明:無
---------------------------------------------------------------------------------------*/
void USART_DMA_SendStart(DMA_Stream_TypeDef *DMA_Streamx, u16 m_u16SendCnt)
{
u16 l_u16RetryCnt = 0;
DMA_Cmd(DMA_Streamx, DISABLE); //關閉DMA傳輸
while ((DMA_GetCmdStatus(DMA_Streamx) != DISABLE) && (l_u16RetryCnt++ < 500)); //等待DMA可配置
DMA_SetCurrDataCounter(DMA_Streamx, m_u16SendCnt); //數據傳輸量
DMA_Cmd(DMA_Streamx, ENABLE); //開啓DMA傳輸
}
/*--------------------------------------------------------------------------------------
函數名稱:void USART1_DMA_SendNByte(u8 *m_pSendBuf, u16 m_u16SendCnt)
函數功能:串口USART1以DMA方式發送多字節函數
入口參數:u8 *m_pSendBuf - 待發送數據緩存, u16 m_u16SendCnt - 待發送數據個數
出口參數:無
說 明:無
---------------------------------------------------------------------------------------*/
void USART1_DMA_SendNByte(u8 *m_pSendBuf, u16 m_u16SendCnt)
{
memcpy(G_u8Usart1SendBuf, m_pSendBuf, m_u16SendCnt);
USART_DMA_SendStart(DMA2_Stream7, m_u16SendCnt); //啓動一次DMA傳輸
}
/*--------------------------------------------------------------------------------------
函數名稱:void DMA2_Stream7_IRQHandler(void)
函數功能:串口USART1以DMA方式發送完成中斷服務程序
入口參數:無
出口參數:無
說 明:無
---------------------------------------------------------------------------------------*/
void DMA2_Stream7_IRQHandler(void)
{
if(DMA_GetFlagStatus(DMA2_Stream7, DMA_FLAG_TCIF7) != RESET) //DMA發送完成?
{
DMA_ClearFlag(DMA2_Stream7, DMA_FLAG_TCIF7 | DMA_FLAG_FEIF7 |
DMA_FLAG_DMEIF7 | DMA_FLAG_TEIF7 | DMA_FLAG_HTIF7); //清除標誌位
while(!USART_GetFlagStatus(USART1, USART_FLAG_TC)); //等待USART1發送完成標誌TC置1
USART_ClearFlag(USART1, USART_FLAG_TC); //清除發送完成標誌
RS485_Recv(); //切換爲RS485接收模式
}
}
/*--------------------------------------------------------------------------------------
函數名稱:void USART1_IRQHandler(void)
函數功能:USART串口1中斷服務程序
入口參數:無
出口參數:無
說 明:無
---------------------------------------------------------------------------------------*/
void USART1_IRQHandler(void)
{
u16 l_u16Temp = 0;
if(USART_GetITStatus(USART1, USART_IT_IDLE) != RESET) //若有空閒中斷
{
DMA_Cmd(DMA2_Stream5, DISABLE); //關閉DMA2_Stream5,防止處理期間有數據
DMA_ClearFlag(DMA2_Stream5, DMA_FLAG_TCIF5 | DMA_FLAG_FEIF5 |
DMA_FLAG_DMEIF5 | DMA_FLAG_TEIF5 | DMA_FLAG_HTIF5); //清除標誌位
//清除USART總線空閒中斷標誌(只要讀USART1->SR和USART1->DR即可)
l_u16Temp = USART1->SR;
l_u16Temp = USART1->DR;
G_u16CommRecvLen = USART1_RECV_MAXLEN - DMA_GetCurrDataCounter(DMA2_Stream5); //求出接收到數據的字節數
if(G_u16CommRecvLen <= USART1_RECV_MAXLEN)
{
RS485_Send(); //RS485發送模式
USART1_DMA_SendNByte(G_u8Usart1RecvBuf, G_u16CommRecvLen); //回送接收到的數據
}
DMA_SetCurrDataCounter(DMA2_Stream5, USART1_RECV_MAXLEN); //設置傳輸數據長度
DMA_Cmd(DMA2_Stream5, ENABLE); //使能DMA2_Stream5
}
}
方法二:用USART1發送完成中斷
/*----------------------------------------------------------------------------------------------------
*Copyright: SXD Tech. Co., Ltd.
*開發 環境: Keil MDK 5.14 && STM32F407ZET6
*文件 名稱: USART串行通信驅動源文件
*作 者: 順信德
*版 本: V1.0
*日 期: 2018-2-6
*說 明:
*修改 日誌: (1)
----------------------------------------------------------------------------------------------------*/
#include "Usart.h"
/*--------------------------------------------變量定義(S)--------------------------------------------*/
u32 G_u32RS485BaudRate = 9600; //RS485通訊波特率
u8 G_u8Usart1SendBuf[USART1_SEND_MAXLEN]={0,}; //發送數據緩衝區
u8 G_u8Usart1RecvBuf[USART1_RECV_MAXLEN]={0,}; //接收數據緩衝區
u16 G_u16CommRecvLen=0; //通訊接收的一幀數據長度
/*--------------------------------------------變量定義(E)--------------------------------------------*/
/*--------------------------------------------函數聲明(S)--------------------------------------------*/
void USART1_Init(u32 baud); //USART1串口初始化
void USART_DMA_SendStart(DMA_Stream_TypeDef *DMA_Streamx, u16 m_u16SendCnt); //串口USART1啓動一次DMA傳輸
void USART1_DMA_SendNByte(u8 *m_pSendBuf, u16 m_u16SendCnt); //串口USART1以DMA方式發送多字節
/*--------------------------------------------函數聲明(E)--------------------------------------------*/
/*----------------------------------------------------------------------------------------------------
*函數名稱:void USART1_Init(u32 baud)
*函數功能:USART1串口初始化函數
*入口參數:u32 baud - 波特率(單位bps)
*出口參數:無
*說 明:用於RS485通信;
----------------------------------------------------------------------------------------------------*/
void USART1_Init(u32 baud)
{
GPIO_InitTypeDef GPIO_InitStructure;
USART_InitTypeDef USART_InitStructure;
NVIC_InitTypeDef NVIC_InitStructure;
DMA_InitTypeDef DMA_InitStructure;
u16 mid_u16RetryCnt = 0;
USART_DeInit(USART1);
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE); //使能GPIOA時鐘
RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE); //使能USART1時鐘
//USART1對應引腳複用映射
GPIO_PinAFConfig(GPIOA, GPIO_PinSource9, GPIO_AF_USART1); //GPIOA9複用爲USART1_TX
GPIO_PinAFConfig(GPIOA, GPIO_PinSource10, GPIO_AF_USART1); //GPIOA10複用爲USART1_RX
//USART1端口配置
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9 | GPIO_Pin_10; //GPIOA9與GPIOA10
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF; //複用功能
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_25MHz; //速度25MHz
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP; //推輓輸出
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP; //上拉
GPIO_Init(GPIOA, &GPIO_InitStructure); //初始化PA9,PA10
//USART1初始化設置
USART_InitStructure.USART_BaudRate = baud; //波特率設置
USART_InitStructure.USART_WordLength = USART_WordLength_8b; //字長爲8位數據格式
USART_InitStructure.USART_StopBits = USART_StopBits_1; //一個停止位
USART_InitStructure.USART_Parity = USART_Parity_No; //無奇偶校驗位
USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None; //無硬件數據流控制
USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx; //收發模式
USART_Init(USART1, &USART_InitStructure); //初始化USART1
USART_Cmd(USART1, ENABLE); //使能USART1
USART_ClearFlag(USART1, USART_FLAG_TC); //清除發送完成標誌
while(USART_GetFlagStatus(USART1, USART_FLAG_TC) == RESET); //等待空閒幀發送完成後再清零發送完成標誌
USART_ClearFlag(USART1, USART_FLAG_TC); //清除發送完成標誌
USART_ITConfig(USART1, USART_IT_TC, ENABLE); //使能USART1傳輸完成中斷
USART_ITConfig(USART1, USART_IT_RXNE, DISABLE); //禁止USART1接收不爲空中斷
USART_ITConfig(USART1, USART_IT_TXE, DISABLE); //禁止USART1發送空中斷
USART_ITConfig(USART1, USART_IT_IDLE, ENABLE); //開啓USART1空閒中斷
//USART1 NVIC配置
NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn; //串口1中斷通道
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=3; //搶佔優先級3
NVIC_InitStructure.NVIC_IRQChannelSubPriority =3; //子優先級3
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; //IRQ通道使能
NVIC_Init(&NVIC_InitStructure);
USART_DMACmd(USART1, USART_DMAReq_Tx, ENABLE); //使能串口1的DMA發送
USART_DMACmd(USART1, USART_DMAReq_Rx, ENABLE); //使能串口1的DMA接收
// - USART1發送DMA配置
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA2,ENABLE); //DMA2時鐘使能
DMA_DeInit(DMA2_Stream7);
while ((DMA_GetCmdStatus(DMA2_Stream7) != DISABLE) && (mid_u16RetryCnt++ < 500)); //等待DMA可配置
//配置DMA2_Stream7
DMA_InitStructure.DMA_Channel = DMA_Channel_4; //通道選擇
DMA_InitStructure.DMA_PeripheralBaseAddr = (u32)&USART1->DR; //DMA外設地址
DMA_InitStructure.DMA_Memory0BaseAddr = (u32)G_u8Usart1SendBuf; //DMA 存儲器0地址
DMA_InitStructure.DMA_DIR = DMA_DIR_MemoryToPeripheral; //存儲器到外設模式
DMA_InitStructure.DMA_BufferSize = USART1_SEND_MAXLEN; //數據傳輸量
DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable; //外設非增量模式
DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable; //存儲器增量模式
DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte; //外設數據長度:8位
DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte; //存儲器數據長度:8位
DMA_InitStructure.DMA_Mode = DMA_Mode_Normal; //使用普通模式
DMA_InitStructure.DMA_Priority = DMA_Priority_Medium; //中等優先級
DMA_InitStructure.DMA_FIFOMode = DMA_FIFOMode_Disable;
DMA_InitStructure.DMA_FIFOThreshold = DMA_FIFOThreshold_Full;
DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single; //存儲器突發單次傳輸
DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single; //外設突發單次傳輸
DMA_Init(DMA2_Stream7, &DMA_InitStructure); //初始化DMA Stream
DMA_Cmd(DMA2_Stream7, ENABLE); //使能DMA2_Stream7
// - USART1接收DMA配置
mid_u16RetryCnt = 0;
DMA_DeInit(DMA2_Stream5);
while ((DMA_GetCmdStatus(DMA2_Stream5) != DISABLE) && (mid_u16RetryCnt++ < 500)); //等待DMA可配置
//配置DMA2_Stream5
DMA_InitStructure.DMA_Channel = DMA_Channel_4; //通道選擇
DMA_InitStructure.DMA_PeripheralBaseAddr = (u32)&USART1->DR; //DMA外設地址
DMA_InitStructure.DMA_Memory0BaseAddr = (u32)G_u8Usart1RecvBuf; //DMA 存儲器0地址
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralToMemory; //外設到存儲器模式
DMA_InitStructure.DMA_BufferSize = USART1_RECV_MAXLEN; //數據傳輸量
DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable; //外設非增量模式
DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable; //存儲器增量模式
DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte; //外設數據長度:8位
DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte; //存儲器數據長度:8位
DMA_InitStructure.DMA_Mode = DMA_Mode_Normal; //使用普通模式
DMA_InitStructure.DMA_Priority = DMA_Priority_Medium; //中等優先級
DMA_InitStructure.DMA_FIFOMode = DMA_FIFOMode_Disable;
DMA_InitStructure.DMA_FIFOThreshold = DMA_FIFOThreshold_Full;
DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single; //存儲器突發單次傳輸
DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single; //外設突發單次傳輸
DMA_Init(DMA2_Stream5, &DMA_InitStructure); //初始化DMA Stream
DMA_Cmd(DMA2_Stream5, ENABLE); //使能DMA2_Stream5
}
/*--------------------------------------------------------------------------------------
函數名稱:void USART_DMA_SendStart(DMA_Stream_TypeDef *DMA_Streamx, u16 m_u16SendCnt)
函數功能:串口USART1啓動一次DMA傳輸函數
入口參數:DMA_Stream_TypeDef DMA_Streamx - DMA數據流(DMA1_Stream0~7/DMA2_Stream0~7);
u16 m_u16SendCnt - 待傳輸數據字節數
出口參數:無
說 明:無
---------------------------------------------------------------------------------------*/
void USART_DMA_SendStart(DMA_Stream_TypeDef *DMA_Streamx, u16 m_u16SendCnt)
{
u16 l_u16RetryCnt = 0;
DMA_Cmd(DMA_Streamx, DISABLE); //關閉DMA傳輸
while ((DMA_GetCmdStatus(DMA_Streamx) != DISABLE) && (l_u16RetryCnt++ < 500)); //等待DMA可配置
DMA_SetCurrDataCounter(DMA_Streamx, m_u16SendCnt); //數據傳輸量
DMA_Cmd(DMA_Streamx, ENABLE); //開啓DMA傳輸
}
/*--------------------------------------------------------------------------------------
函數名稱:void USART1_DMA_SendNByte(u8 *m_pSendBuf, u16 m_u16SendCnt)
函數功能:串口USART1以DMA方式發送多字節函數
入口參數:u8 *m_pSendBuf - 待發送數據緩存, u16 m_u16SendCnt - 待發送數據個數
出口參數:無
說 明:無
---------------------------------------------------------------------------------------*/
void USART1_DMA_SendNByte(u8 *m_pSendBuf, u16 m_u16SendCnt)
{
memcpy(G_u8Usart1SendBuf, m_pSendBuf, m_u16SendCnt);
USART_DMA_SendStart(DMA2_Stream7, m_u16SendCnt); //啓動一次DMA傳輸
}
/*--------------------------------------------------------------------------------------
函數名稱:void USART1_IRQHandler(void)
函數功能:USART串口1中斷服務程序
入口參數:無
出口參數:無
說 明:無
---------------------------------------------------------------------------------------*/
void USART1_IRQHandler(void)
{
u16 l_u16Temp = 0;
if(USART_GetITStatus(USART1, USART_IT_IDLE) != RESET) //若有空閒中斷
{
DMA_Cmd(DMA2_Stream5, DISABLE); //關閉DMA2_Stream5,防止處理期間有數據
DMA_ClearFlag(DMA2_Stream5, DMA_FLAG_TCIF5 | DMA_FLAG_FEIF5 |
DMA_FLAG_DMEIF5 | DMA_FLAG_TEIF5 | DMA_FLAG_HTIF5);//清零標誌位
//清除USART總線空閒中斷標誌(只要讀USART1->SR和USART1->DR即可)
l_u16Temp = USART1->SR;
l_u16Temp = USART1->DR;
G_u16CommRecvLen = USART1_RECV_MAXLEN - DMA_GetCurrDataCounter(DMA2_Stream5); //求出接收到數據的字節數
if(G_u16CommRecvLen <= USART1_RECV_MAXLEN)
{
RS485_Send(); //RS485發送模式
USART1_DMA_SendNByte(G_u8Usart1RecvBuf, G_u16CommRecvLen);
}
DMA_SetCurrDataCounter(DMA2_Stream5, USART1_RECV_MAXLEN); //設置傳輸數據長度
DMA_Cmd(DMA2_Stream5, ENABLE); //使能DMA2_Stream5
}
if(USART_GetITStatus(USART1, USART_IT_TC) != RESET) //若有發送完成中斷
{
USART_ClearITPendingBit(USART1, USART_IT_TC); //清除USART1發送完成中斷標誌
DMA_ClearFlag(DMA2_Stream7, DMA_FLAG_TCIF7 | DMA_FLAG_FEIF7 |
DMA_FLAG_DMEIF7 | DMA_FLAG_TEIF7 | DMA_FLAG_HTIF7);//清零標誌位
RS485_Recv(); //切換爲RS485接收模式
}
}
6、聲明
本程序的收發機制只是簡單的處理機制,只是爲了說明解決數據丟失字節問題的方法,對進行快速大數據通訊時會出現亂碼。所以,用於實際項目中,需對此程序的收發處理機制進行重新設計。兩種方法中,個人認爲方法二更好,因爲方法一在中斷裏面等待白白耗費了時間。
希望可以幫助到遇到同樣問題的朋友,共同進步!同時,如有錯漏之處,歡迎評論指正,不勝感激!轉載此文請註明出處,謝謝!