STM32 USART3使用DMA接收数据被覆盖出错
最近一项目调试中发现stm32的usart3在工作在dma接收模式下，如果接收数据超出了DMA1_Channel3->CNDTR的指定的长度，会覆盖且只覆盖接收buf。
比如:参数配置CNDTR=3，而当发送在单片机接收引脚上的帧数据为0x01,0x02,0x03,0x04,0x05共5个字节，当DMA接收第3个字节0x03后，CNDTR=0 DMA停止读取串口接收数据，然后软件重新修改CNDTR=3，开启MDA接收功能等待发送到RX上的下一帧数据。问题来了，此时如果RX上没有接收到任何数据的情况先，DMA会自动将上一帧的0x04写入到buf，同时CNDTR被减一变为2。
感觉上一帧数据在CNDTR等于0时还是会触发一次DMA接收，当CNDTR重新不等于0以后就开始执行读操作。
附上调试代码，请高手指点，谢谢！！
[*]#include "stm32f10x.h"
[*]#include <string.h>
[*]
[*]/* 无符号类型 */
[*]typedef uint8_t INT8U;
[*]typedef uint16_t INT16U;
[*]typedef uint32_t INT32U;
[*]typedef uint64_t INT64U;
[*]
[*]/* 有符号类型 */
[*]typedef int8_t INT8;
[*]typedef int16_t INT16;
[*]typedef int32_t INT32;
[*]typedef int64_t INT64;
[*]
[*]typedef ErrorStatus RESULT_STATE;
[*]
[*]#define DEF_COM_RECV_BUF_SIZE50
[*]#define DEF_COM_SEND_BUF_SIZE50
[*]
[*]struct
[*]{
[*]INT8U SendBuf;
[*]INT8U RecvBuf;
[*]INT16U RecvLen;
[*]INT8U fSending :1;
[*]INT8U fRecv :1;
[*]}sCom;
[*]
[*]static void HW_ComCfg (void)
[*]{
[*]/* GPIOB & AFIO Periph clock enable */
[*]RCC->APB2ENR |= RCC_APB2ENR_IOPBEN;
[*]RCC->APB2ENR |= RCC_APB2ENR_AFIOEN;
[*]
[*]/* PB10 USART3_Tx */
[*]GPIOB->CRH = (GPIOB->CRH & (~GPIO_CRH_MODE10)) | GPIO_CRH_MODE10_1; /* Output mode, max speed 2 MHz */
[*]GPIOB->CRH = (GPIOB->CRH & (~GPIO_CRH_CNF10)) | GPIO_CRH_CNF10_1; /* Alternate functionoutput Push-pull */
[*]/* PB11 USART3_Rx */
[*]GPIOB->CRH = (GPIOB->CRH & (~GPIO_CRH_MODE11)); /* input */
[*]GPIOB->CRH = (GPIOB->CRH & (~GPIO_CRH_CNF11)) | GPIO_CRH_CNF11_0; /* Floating input */
[*]
[*]/* Enable USART3 Clock */
[*]RCC->APB1ENR |= RCC_APB1ENR_USART3EN;
[*]
[*]/* 1Start/9Data/1Stop */
[*]USART3->CR1 |= USART_CR1_M; /* 1 Start bit, 9 Data bits, n Stop bit */
[*]USART3->CR1 |= USART_CR1_PCE; /* Parity control enable */
[*]USART3->CR1 |= USART_CR1_PS; /* Odd parity */
[*]USART3->CR2 &= ~USART_CR2_STOP; /* 1 Stop bit */
[*]
[*]/* baud 115200bps */
[*]USART3->BRR = (INT32U)(((72000000ul/2)/115200/16 << 4) /* DIV_Mantissa */
[*] | ((INT64U)(72000000ul/2)*10000/115200/16 - (72000000ul/2)/115200/16*10000)*16/10000); /* DIV_Fraction */
[*]
[*]/* DMA for transmission */
[*]USART3->CR3 |= USART_CR3_DMAT; /* transmission DMA enabled */
[*]
[*]/* DMA1 channel2 */
[*]RCC->AHBENR |= RCC_AHBENR_DMA1EN; /* Enable DMA1 Clock */
[*]DMA1_Channel2->CCR = (DMA1_Channel2->CCR & (~DMA_CCR2_PL)) | DMA_CCR2_PL_0; /* Channel priority level: medium */
[*]DMA1_Channel2->CCR = (DMA1_Channel2->CCR & (~DMA_CCR2_MSIZE)); /* Memory size:8-bits */
[*]DMA1_Channel2->CCR = (DMA1_Channel2->CCR & (~DMA_CCR2_PSIZE)); /* Peripheral size:8-bits */
[*]DMA1_Channel2->CCR |= DMA_CCR2_MINC; /* Memory increment mode enabled */
[*]DMA1_Channel2->CCR &= ~DMA_CCR2_PINC; /* Peripheral increment mode disabled */
[*]DMA1_Channel2->CCR |= DMA_CCR2_DIR; /* Read from memory */
[*]DMA1_Channel2->CPAR = (INT32U)&USART3->DR; /* Peripheral address */
[*]
[*]/* DMA for receive */
[*]USART3->CR3 |= USART_CR3_DMAR; /* receive DMA enabled */
[*]
[*]/* DMA1 channel3 */
[*]DMA1_Channel3->CCR = (DMA1_Channel3->CCR & (~DMA_CCR3_PL)) | DMA_CCR3_PL_1; /* Channel priority level: high */
[*]DMA1_Channel3->CCR = (DMA1_Channel3->CCR & (~DMA_CCR3_PSIZE)); /* Peripheral size:8-bits */
[*]DMA1_Channel3->CCR = (DMA1_Channel3->CCR & (~DMA_CCR3_MSIZE)); /* Memory size:8-bits */
[*]DMA1_Channel3->CCR &= ~DMA_CCR3_PINC; /* Peripheral increment mode disabled */
[*]DMA1_Channel3->CCR |= DMA_CCR3_MINC; /* Memory increment mode enabled */
[*]DMA1_Channel3->CCR &= ~DMA_CCR3_DIR; /* Read from Peripheral */
[*]DMA1_Channel3->CPAR = (INT32U)&USART3->DR; /* Peripheral address */
[*]
[*]/* interrupt */
[*]USART3->CR1 |= USART_CR1_IDLEIE; /* IDLE */
[*]
[*]/* USART enable */
[*]USART3->CR1 |= USART_CR1_TE | USART_CR1_RE; /* Transmitter and Receiver enable */
[*]USART3->CR1 |= USART_CR1_UE; /* USART prescaler and outputs enabled */
[*]}
[*]
[*]RESULT_STATE Com_Send (INT8U *p_data, INT16U len)
[*]{
[*]if (sCom.fSending)
[*]{
[*] return ERROR;
[*]}
[*]
[*]if (len > DEF_COM_SEND_BUF_SIZE || len == 0)
[*]{
[*] return ERROR;
[*]}
[*]
[*]memcpy(&sCom.SendBuf, p_data, len);
[*]DMA1_Channel2->CCR &= ~DMA_CCR2_EN; /* Channel disabled */
[*]DMA1_Channel2->CNDTR = (INT32U)len; /* Number of data to transfer */
[*]DMA1_Channel2->CCR |= DMA_CCR2_EN; /* Channel enabled */
[*]USART3->CR1 |= USART_CR1_TCIE; /* TC */
[*]sCom.fSending = 1;
[*]
[*]return SUCCESS;
[*]}
[*]
[*]void ComInit (void)
[*]{
[*]DMA1_Channel2->CMAR = (INT32U)&sCom.SendBuf; /* Memory address */
[*]
[*]DMA1_Channel3->CCR &= ~DMA_CCR3_EN; /* Channel disabled */
[*]DMA1_Channel3->CMAR = (INT32U)&sCom.RecvBuf; /* Memory address */
[*]DMA1_Channel3->CNDTR = (INT32U)sizeof(sCom.RecvBuf); /* Number of data to transfer */
[*]DMA1_Channel3->CCR |= DMA_CCR3_EN; /* Channel enabled */
[*]}
[*]
[*]static void HW_InterruptCfg (void)
[*]{
[*]NVIC_InitTypeDef NVIC_InitStructure;
[*]
[*]/* Configures the priority grouping */
[*]NVIC_PriorityGroupConfig(NVIC_PriorityGroup_1);
[*]
[*]/* COM */
[*]NVIC_InitStructure.NVIC_IRQChannel = USART3_IRQn;
[*]NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;
[*]NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
[*]NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
[*]NVIC_Init(&NVIC_InitStructure);
[*]}
[*]
[*]void USART3_IRQHandler(void)
[*]{
[*]/* Transmission complete */
[*]if (sCom.fSending && (USART3->SR & USART_SR_TC))
[*]{
[*] USART3->CR1 &= ~USART_CR1_TCIE; /* TCIE */
[*] sCom.fSending = 0;
[*]}
[*]
[*]/* IDLE line detected */
[*]if (USART3->SR & USART_SR_IDLE)
[*]{
[*] sCom.RecvLen = (INT32U)sizeof(sCom.RecvBuf) - DMA1_Channel3->CNDTR;
[*]
[*] DMA1_Channel3->CCR &= ~DMA_CCR3_EN; /* Channel disabled */
[*] DMA1->IFCR |= DMA_IFCR_CGIF3;
[*] DMA1_Channel3->CNDTR = (INT32U)sizeof(sCom.RecvBuf); /* Number of data to transfer */
[*] DMA1_Channel3->CCR |= DMA_CCR3_EN; /* Channel enabled */
[*]
[*] if (USART3->SR & (USART_SR_NE | USART_SR_FE | USART_SR_PE)) /* Noise/Framing/Parity error is detected */
[*] {
[*] }
[*] else
[*] {
[*] sCom.fRecv = 1;
[*] }
[*]
[*] INT32U sr = USART3->SR; /* clear sr */
[*] INT32U dr = USART3->DR; /* clear dr */
[*]}
[*]}
[*]
[*]void main (void)
[*]{
[*]HW_ComCfg();
[*]HW_InterruptCfg();
[*]ComInit();
[*]
[*]while (1)
[*]{
[*] if (sCom.fRecv)
[*] {
[*] Com_Send(&sCom.RecvBuf, sCom.RecvLen);
[*] sCom.fRecv = 0;
[*] }
[*]}
[*]}
[*]
既然要这样的话，再重启DMA前，你把RXNE也清下看看。
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