USART是一种异步通信，不带有时钟同步信号，而且是全双工，允许数据同时在两个方向上传输。
而DMA就是在I/O设备和内存的数据传输的时候，数据搬运工作全部交给DMA控制器，而CPU不再参与任何与数据搬运相关的事情，这样CPU就可以去处理别的数据。
对于这个USART+DMA传输+串口空闲中断就极大的减少CPU的消耗，可以用CPU去做更多的事情。
废话不都说，上代码，代码是stm32ZGT6的芯片上的代码
#include "sys.h"
#include "usart.h"
#include "dma.h"
#include "led.h"#if 1
#pragma import(__use_no_semihosting) struct __FILE
{ int handle; }; FILE __stdout; void _sys_exit(int x)
{ x = x;
} int fputc(int ch, FILE *f)
{ while((USART1->SR&0X40)==0); USART1->DR = (u8) ch; return ch;
}
#endif /*
int fputc(int ch, FILE *f)
{USART_SendData(USART1, (uint8_t) ch);while (USART_GetFlagStatus(USART1, USART_FLAG_TC) == RESET) {} return ch;
}
int GetKey (void) { while (!(USART1->SR & USART_FLAG_RXNE));return ((int)(USART1->DR & 0x1FF));
}
*/#if EN_USART1_RX //??????????????u8 USART_RX_BUF[USART_REC_LEN]; u16 rx_len;
u8 i;void uart_init(u32 bound)
{GPIO_InitTypeDef GPIO_InitStructure;USART_InitTypeDef USART_InitStructure;NVIC_InitTypeDef NVIC_InitStructure;RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1|RCC_APB2Periph_GPIOA, ENABLE); GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9; GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP; GPIO_Init(GPIOA, &GPIO_InitStructure);//??????GPIOA.9GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;//PA10GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;GPIO_Init(GPIOA, &GPIO_InitStructure);//??????GPIOA.10 NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=3 ;NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3; NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; NVIC_Init(&NVIC_InitStructure); USART_InitStructure.USART_BaudRate = bound;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); USART_ITConfig(USART1,USART_IT_IDLE, ENABLE);USART_Cmd(USART1, ENABLE); }void USART1_IRQHandler(void)
{
#if SYSTEM_SUPPORT_OS //????SYSTEM_SUPPORT_OS???????ò?è???§??OS.OSIntEnter();
#endifif(USART_GetITStatus(USART1, USART_IT_IDLE) != RESET) {i=USART1->SR;i=USART1->DR; USART_ClearITPendingBit(USART1,USART_IT_IDLE);MYDMA_Enable(DMA1_Channel5); LED1=!LED1; }
#if SYSTEM_SUPPORT_OS OSIntExit();
#endif
}
#endif ：
u8 ReceiveBuff[RECEIVE_BUF_SIZE];
u8 SendBuff[SEND_BUF_SIZE];
const u8 TEXT_TO_SEND[]={"ALIENTEK WarShip STM32F1 DMA ???????é"};int main(void){ u16 i;u8 t=0;u8 j,mask=0;delay_init(); NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);uart_init(115200); LED_Init(); LCD_Init(); KEY_Init(); Usart_Tx_Config();Usart_Rx_Config();//MYDMA_Config(DMA1_Channel4,(u32)&USART1->DR,(u32)SendBuff,SEND_BUF_SIZE);//DMA1?¨??4,???è??????1,?????÷??SendBuff,?¤??SEND_BUF_SIZE.//MYDMA_Config(DMA1_Channel5,(u32)&USART1->DR,(u32)ReceiveBuff,RECEIVE_BUF_SIZE);//DMA?¨??5?????è????5?????ü?÷receive,?¤??8200POINT_COLOR=RED;LCD_ShowString(30,50,200,16,16,"WarShip STM32"); LCD_ShowString(30,70,200,16,16,"DMA TEST"); LCD_ShowString(30,90,200,16,16,"ATOM@ALIENTEK");LCD_ShowString(30,110,200,16,16,"2015/1/15"); LCD_ShowString(30,130,200,16,16,"KEY0:Start");j=sizeof(TEXT_TO_SEND); for(i=0;i<SEND_BUF_SIZE;i++){if(t>=j){if(mask){SendBuff[i]=0x0a;t=0;}else {SendBuff[i]=0x0d;mask++;} }else{mask=0;SendBuff[i]=TEXT_TO_SEND[t];t++;} } POINT_COLOR=BLUE; i=0;while(1){t=KEY_Scan(0);if(t==KEY0_PRES){LCD_ShowString(30,150,200,16,16,"Start Transimit....");LCD_ShowString(30,170,200,16,16," %");//????°?·??? USART_DMACmd(USART1,USART_DMAReq_Tx,ENABLE);MYDMA_Enable(DMA1_Channel4);}i++;delay_ms(10);if(i==20){LED0=!LED0;i=0;} }
}#ifndef __USART_H
#define __USART_H
#include "stdio.h"
#include "sys.h" #define USART_REC_LEN 200
#define EN_USART1_RX 1 extern u8 USART_RX_BUF[USART_REC_LEN];
extern u16 USART_RX_STA; void uart_init(u32 bound);
#endif
#include "dma.h"
#include "lcd.h"DMA_InitTypeDef DMA_InitStructure;
NVIC_InitTypeDef NVIC_InitStructure;u16 DMA1_MEM_LEN;void Usart_Tx_Config()
{RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1,ENABLE);DMA_DeInit(DMA1_Channel4);DMA1_MEM_LEN=SEND_BUF_SIZE;DMA_InitStructure.DMA_PeripheralBaseAddr=(u32)&USART1->DR;DMA_InitStructure.DMA_MemoryBaseAddr=(u32)SendBuff;DMA_InitStructure.DMA_DIR=DMA_DIR_PeripheralDST;DMA_InitStructure.DMA_BufferSize=(u32)SEND_BUF_SIZE;DMA_InitStructure.DMA_PeripheralInc=DMA_PeripheralInc_Disable;DMA_InitStructure.DMA_PeripheralDataSize=DMA_PeripheralDataSize_Byte; DMA_InitStructure.DMA_MemoryInc=DMA_MemoryInc_Enable; 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_Channel4,&DMA_InitStructure); NVIC_InitStructure.NVIC_IRQChannel=DMA1_Channel4_IRQn; NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=3;NVIC_InitStructure.NVIC_IRQChannelSubPriority=3; NVIC_InitStructure.NVIC_IRQChannelCmd=ENABLE; NVIC_Init(&NVIC_InitStructure); DMA_ITConfig(DMA1_Channel4,DMA_IT_TC,ENABLE); USART_DMACmd(USART1,USART_DMAReq_Tx,ENABLE);DMA_Cmd(DMA1_Channel4,ENABLE);
}void Usart_Rx_Config()
{RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1,ENABLE);DMA_DeInit(DMA1_Channel5);DMA1_MEM_LEN=RECEIVE_BUF_SIZE;DMA_InitStructure.DMA_PeripheralBaseAddr=(u32)&USART1->DR;DMA_InitStructure.DMA_MemoryBaseAddr=(u32)ReceiveBuff;DMA_InitStructure.DMA_DIR=DMA_DIR_PeripheralDST;DMA_InitStructure.DMA_BufferSize=(u32)RECEIVE_BUF_SIZE;DMA_InitStructure.DMA_PeripheralInc=DMA_PeripheralInc_Disable;DMA_InitStructure.DMA_PeripheralDataSize=DMA_PeripheralDataSize_Byte; DMA_InitStructure.DMA_MemoryInc=DMA_MemoryInc_Enable; 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_Channel5,&DMA_InitStructure); USART_DMACmd(USART1,USART_DMAReq_Rx,ENABLE);DMA_Cmd(DMA1_Channel5,ENABLE);
}void MYDMA_Enable(DMA_Channel_TypeDef*DMA_CHx)
{DMA_Cmd(DMA_CHx,DISABLE); DMA_SetCurrDataCounter(DMA_CHx,DMA1_MEM_LEN);DMA_Cmd(DMA_CHx,ENABLE);
}void DMA1_Channel4_IRQHandler(void)
{if(DMA_GetFlagStatus(DMA1_FLAG_TC4)!=RESET){DMA_ClearFlag(DMA1_FLAG_TC4);DMA_Cmd(DMA1_Channel4,DISABLE);DMA_ClearITPendingBit(DMA1_FLAG_TC4); LCD_ShowNum(30,170,100,3,16);LCD_ShowString(30,150,200,16,16,"Transimit Finished!");}
}#ifndef __DMA_H
#define __DMA_H
#include "sys.h"#define SEND_BUF_SIZE 8200
#define RECEIVE_BUF_SIZE 8200extern u8 ReceiveBuff[RECEIVE_BUF_SIZE];
extern u8 SendBuff[SEND_BUF_SIZE]; void Usart_Tx_Config(void);
void Usart_Rx_Config(void);void MYDMA_Enable(DMA_Channel_TypeDef*DMA_CHx);#endif