1 前言

本章介绍下如何使用uart的rx和tx功能，其中tx利用dma更为方便。

2 基础

参考文章：STM32单片机串口空闲中断+DMA接收不定长数据

uart一次只能收发一字节数据，所以发送相对简单点，直接用函数USART_SendData()，发送多个数据。
但是rx接收时需要等uart状态rx结束，读取到USART_FLAG_RXDNE状态可以收数据。
不过使用dma更为方便，使用usart目录下的DMA_polling示例。

简单介绍下dma：在内存中开辟一段数组空间，uart收到数据后将存入dma中，指针向后移动，直到填满后产生dma中断。
dma中断中可以配置清空等操作。

3 引脚介绍

整理了一下开发板的uart端口。
其中usart有三个，分别为usart1-3，uart有四个，分别为uart4-7。
usart相对uart多了时钟信号，用于同步。

其中uart4一般作为和电脑的串口通信，用于打印信息。printf函数显示log就通过uart4传输出来。

4 硬件

usart3和uart5-7，分别为PC10/11，PB13/14，PB0/1，PC4/5。

uart4根据电路图来看是接到了PA2/3。推测PA2/3和PA13/12有关联，因为PA13/12是microusb数据线。

5 代码

主要参考两个示例，usart/printf是用于打印log，usart/dma_polling是用于dma接收数据。

printf示例：https://gitee.com/CMIOT-XinShengTech/CMIOT.CM32M4xxR_Library/tree/main/Projects/CM32M433R-START/Examples/USART/Printf

示例源码路径：https://gitee.com/CMIOT-XinShengTech/CMIOT.CM32M4xxR_Library/tree/main/Projects/CM32M433R-START/Examples/USART/DMA_Polling

打印log使用的uart4，用到的io为PD0/1。
uart收发使用的uart5，用到io为PB13/14。

5.1 main.h

头文件定义uart引脚和dma信息。

/*******************************************************************************
*
* COPYRIGHT(c) 2020, China Mobile IOT
*
* Redistribution and use in source and binary forms, with or without modification,
* are permitted provided that the following conditions are met:
*   1. Redistributions of source code must retain the above copyright notice,
*      this list of conditions and the following disclaimer.
*   2. Redistributions in binary form must reproduce the above copyright notice,
*      this list of conditions and the following disclaimer in the documentation
*      and/or other materials provided with the distribution.
*   3. Neither the name of China Mobile IOT nor the names of its contributors
*      may be used to endorse or promote products derived from this software
*      without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*******************************************************************************//*** @file main.h* @author CMIOT Firmware Team* @version v1.0.0** @copyright Copyright (c) 2020, CMIOT. All rights reserved.*/#ifndef __MAIN_H__
#define __MAIN_H__#ifdef __cplusplus
extern "C" {#endif#include "nuclei_sdk_soc.h"/* USARTx configuration */
#define _USART4_COM_#ifdef _USART4_COM_
#define USARTx              UART4
#define USARTx_GPIO         GPIOD
#define USARTx_CLK          RCC_APB1_PERIPH_UART4
#define USARTx_GPIO_CLK     RCC_APB2_PERIPH_GPIOD
#define USARTx_RxPin        GPIO_PIN_1
#define USARTx_TxPin        GPIO_PIN_0#define GPIO_APBxClkCmd       RCC_EnableAPB2PeriphClk
#define USART_APBxClkCmd    RCC_EnableAPB1PeriphClk
#endif#define _USART5_USART6_#ifdef _USART5_USART6_
#define USARTy                      UART5
#define USARTy_GPIO                 GPIOB
#define USARTy_CLK                  RCC_APB1_PERIPH_UART5
#define USARTy_GPIO_CLK             RCC_APB2_PERIPH_GPIOB
#define USARTy_TxPin                GPIO_PIN_13
#define USARTy_RxPin                GPIO_PIN_14
#define USARTy_APBxClkCmd           RCC_EnableAPB1PeriphClk
#define USARTy_DMAx                 DMA1
#define USARTy_DMAx_CLK             RCC_AHB_PERIPH_DMA1
#define USARTy_DR_Base              (UART5_BASE + 0x04)
#define USARTy_Tx_DMA_Channel       DMA1_CH1
#define USARTy_Tx_DMA_FLAG          DMA1_FLAG_TC1
#define USARTy_Rx_DMA_Channel       DMA1_CH8
#define USARTy_Rx_DMA_FLAG          DMA1_FLAG_TC8
#define USARTy_Tx_DMA_IRQn          DMA1_Channel1_IRQn
#define USARTy_Tx_DMA_IRQHandler    DMA1_Channel1_IRQHandler
#define USARTy_Tx_DMA_INT           DMA1_INT_TXC1#define USARTz                      UART6
#define USARTz_GPIO                 GPIOB
#define USARTz_CLK                  RCC_APB2_PERIPH_UART6
#define USARTz_GPIO_CLK             RCC_APB2_PERIPH_GPIOB
#define USARTz_TxPin                GPIO_PIN_0
#define USARTz_RxPin                GPIO_PIN_1
#define USARTz_APBxClkCmd           RCC_EnableAPB2PeriphClk
#define USARTz_DMAx                 DMA2
#define USARTz_DMAx_CLK             RCC_AHB_PERIPH_DMA2
#define USARTz_DR_Base              (UART6_BASE + 0x04)
#define USARTz_Tx_DMA_Channel       DMA2_CH2
#define USARTz_Tx_DMA_FLAG          DMA2_FLAG_TC2
#define USARTz_Rx_DMA_Channel       DMA2_CH1
#define USARTz_Rx_DMA_FLAG          DMA2_FLAG_TC1
#define USARTz_Rx_DMA_IRQn          DMA2_Channel1_IRQn
#define USARTz_Rx_DMA_IRQHandler    DMA2_Channel1_IRQHandler
#define USARTz_Rx_DMA_INT           DMA2_INT_TXC1
#define USARTz_IRQn                 UART6_IRQn
#endif#ifdef __cplusplus
}
#endif#endif /* __MAIN_H__ */

5.2 main.c

实现uart测试功能。

测试1：dma的tx传输
测试2：uart传输字符串
测试3：dma的rx接收

/*******************************************************************************
*
* COPYRIGHT(c) 2020, China Mobile IOT
*
* Redistribution and use in source and binary forms, with or without modification,
* are permitted provided that the following conditions are met:
*    1. Redistributions of source code must retain the above copyright notice,
*       this list of conditions and the following disclaimer.
*    2. Redistributions in binary form must reproduce the above copyright notice,
*       this list of conditions and the following disclaimer in the documentation
*       and/or other materials provided with the distribution.
*    3. Neither the name of China Mobile IOT nor the names of its contributors
*       may be used to endorse or promote products derived from this software
*       without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*******************************************************************************//*** @file main.c* @author CMIOT Firmware Team* @version v1.0.0** @copyright Copyright (c) 2020, CMIOT. All rights reserved.*/#include <stdio.h>
#include "main.h"/** @addtogroup CM32M4xxR_StdPeriph_Examples* @{*//** @addtogroup USART_DMA_Polling* @{*/typedef enum
{FAILED = 0,PASSED = !FAILED
} TestStatus;#define TxBufferSize1 (countof(TxBuffer1) - 1)
#define TxBufferSize2 (countof(TxBuffer2) - 1)#define countof(a) (sizeof(a) / sizeof(*(a)))USART_InitType USART_InitStructure;
uint8_t TxBuffer1[] = "USART DMA Polling: USARTy -> USARTz using DMA";
uint8_t TxBuffer2[] = "USART DMA Polling: USARTz -> USARTy using DMA";
uint8_t RxBuffer1[TxBufferSize2];
uint8_t RxBuffer2[TxBufferSize1];
volatile TestStatus TransferStatus1 = FAILED;
volatile TestStatus TransferStatus2 = FAILED;void RCC_Configuration(void);
void GPIO_Configuration(void);
void DMA_Configuration(void);// youkai add
void func_init_uart4();
void print_dma();bool status_wait_uart = false;
#define UART_STATUS_RX true
#define UART_STATUS_TX falsevoid print_uart_wait();
void print_uart_wait_end();void reset_dma_rx();
void reset_dma_tx();
void myUart_rx(uint8_t uart_id,bool rx_tx);
void myUart_tx(uint8_t uart_id,uint8_t * data,uint8_t len_send);
void myUart_senddata(uint8_t uart_id, uint8_t * data,uint8_t len_send);void myDMA_tx(uint8_t uart_id);void delay(vu32 nCount);/*** @brief  Main program*/
int main(void)
{func_init_uart4();printf("start init\r\n");printf("-------test1: dma tx---------\r\n");/* System Clocks Configuration */RCC_Configuration();/* Configure the GPIO ports */GPIO_Configuration();/* Configure the DMA */DMA_Configuration();/* USARTy and USARTz configuration ------------------------------------------------------*/USART_InitStructure.BaudRate            = 115200;USART_InitStructure.WordLength          = USART_WL_8B;USART_InitStructure.StopBits            = USART_STPB_1;USART_InitStructure.Parity              = USART_PE_NO;USART_InitStructure.HardwareFlowControl = USART_HFCTRL_NONE;USART_InitStructure.Mode                = USART_MODE_RX | USART_MODE_TX;/* Configure USARTy and USARTz */USART_Init(USARTy, &USART_InitStructure);USART_Init(USARTz, &USART_InitStructure);//    strcpy(TxBuffer1,"hihihihihihihihihihihihihihihihihihihihihihih");
//    printf("TxBuffer1 = [%s]\r\n",(char*)TxBuffer1);/* Enable USARTy DMA Rx and TX request */USART_EnableDMA(USARTy, USART_DMAREQ_RX | USART_DMAREQ_TX, ENABLE);/* Enable USARTz DMA Rx and TX request */USART_EnableDMA(USARTz, USART_DMAREQ_RX | USART_DMAREQ_TX, ENABLE);/* Enable USARTy TX DMA1 Channel */DMA_EnableChannel(USARTy_Tx_DMA_Channel, ENABLE);/* Enable USARTy RX DMA1 Channel */DMA_EnableChannel(USARTy_Rx_DMA_Channel, ENABLE);/* Enable USARTz TX DMA1 Channel */DMA_EnableChannel(USARTz_Tx_DMA_Channel, ENABLE);/* Enable USARTz RX DMA1 Channel */DMA_EnableChannel(USARTz_Rx_DMA_Channel, ENABLE);/* Enable the USARTy and USARTz */USART_Enable(USARTy, ENABLE);USART_Enable(USARTz, ENABLE);// wait until dma send data ok.while(DMA_GetFlagStatus(DMA1_FLAG_TC1,USARTy_DMAx)==RESET){}printf("\r\n-------test2: uart tx---------\r\n");delay(1000);printf("dma tx over.\r\n");//    USART_SendData(USARTy,'\n');
//    delay();char temp_rx[]="hihihi";myUart_tx(5,temp_rx,4);
//    reset_dma_rx();printf("\r\n-------test3: uart rx---------\r\n");int count = 0;while (1){printf("count = %d\r\n",count++);myUart_rx(5,UART_STATUS_RX);}
}/*** @brief  Configures the different system clocks.*/
void RCC_Configuration(void)
{/* DMA clock enable */RCC_EnableAHBPeriphClk(USARTy_DMAx_CLK, ENABLE);RCC_EnableAHBPeriphClk(USARTz_DMAx_CLK, ENABLE);/* Enable GPIO clock */RCC_EnableAPB2PeriphClk(USARTy_GPIO_CLK | USARTz_GPIO_CLK | RCC_APB2_PERIPH_AFIO, ENABLE);/* Enable USARTy and USARTz Clock */USARTy_APBxClkCmd(USARTy_CLK, ENABLE);USARTz_APBxClkCmd(USARTz_CLK, ENABLE);
}/*** @brief  Configures the different GPIO ports.*/
void GPIO_Configuration(void)
{GPIO_InitType GPIO_InitStructure;GPIO_ConfigPinRemap(GPIO_RMP_USART1,ENABLE);/* Configure USARTy Rx as input floating */GPIO_InitStructure.Pin       = USARTy_RxPin;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;GPIO_Init(USARTy_GPIO, &GPIO_InitStructure);/* Configure USARTz Rx as input floating */GPIO_InitStructure.Pin = USARTz_RxPin;GPIO_Init(USARTz_GPIO, &GPIO_InitStructure);/* Configure USARTy Tx as alternate function push-pull */GPIO_InitStructure.Pin        = USARTy_TxPin;GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;GPIO_InitStructure.GPIO_Mode  = GPIO_Mode_AF_PP;GPIO_Init(USARTy_GPIO, &GPIO_InitStructure);/* Configure USARTz Tx as alternate function push-pull */GPIO_InitStructure.Pin = USARTz_TxPin;GPIO_Init(USARTz_GPIO, &GPIO_InitStructure);GPIO_ConfigPinRemap(GPIO_RMP1_UART5, ENABLE);GPIO_ConfigPinRemap(GPIO_RMP3_UART6, ENABLE);
}/*** @brief  Configures the DMA.*/
void DMA_Configuration(void)
{DMA_InitType DMA_InitStructure;/* USARTy TX DMA1 Channel (triggered by USARTy Tx event) Config */DMA_DeInit(USARTy_Tx_DMA_Channel);DMA_InitStructure.PeriphAddr     = USARTy_DR_Base;DMA_InitStructure.MemAddr        = (uint32_t)TxBuffer1;DMA_InitStructure.Direction      = DMA_DIR_PERIPH_DST;DMA_InitStructure.BufSize        = TxBufferSize1;DMA_InitStructure.PeriphInc      = DMA_PERIPH_INC_DISABLE;DMA_InitStructure.DMA_MemoryInc  = DMA_MEM_INC_ENABLE;DMA_InitStructure.PeriphDataSize = DMA_PERIPH_DATA_SIZE_BYTE;DMA_InitStructure.MemDataSize    = DMA_MEMORY_DATA_SIZE_BYTE;DMA_InitStructure.CircularMode   = DMA_MODE_NORMAL;DMA_InitStructure.Priority       = DMA_PRIORITY_VERY_HIGH;DMA_InitStructure.Mem2Mem        = DMA_M2M_DISABLE;DMA_Init(USARTy_Tx_DMA_Channel, &DMA_InitStructure);/* USARTy RX DMA1 Channel (triggered by USARTy Rx event) Config */DMA_DeInit(USARTy_Rx_DMA_Channel);DMA_InitStructure.PeriphAddr = USARTy_DR_Base;DMA_InitStructure.MemAddr    = (uint32_t)RxBuffer1;DMA_InitStructure.Direction  = DMA_DIR_PERIPH_SRC;DMA_InitStructure.BufSize    = TxBufferSize2;DMA_Init(USARTy_Rx_DMA_Channel, &DMA_InitStructure);/* USARTz TX DMA1 Channel (triggered by USARTz Tx event) Config */DMA_DeInit(USARTz_Tx_DMA_Channel);DMA_InitStructure.PeriphAddr = USARTz_DR_Base;DMA_InitStructure.MemAddr    = (uint32_t)TxBuffer2;DMA_InitStructure.Direction  = DMA_DIR_PERIPH_DST;DMA_InitStructure.BufSize    = TxBufferSize2;DMA_Init(USARTz_Tx_DMA_Channel, &DMA_InitStructure);/* USARTz RX DMA1 Channel (triggered by USARTz Rx event) Config */DMA_DeInit(USARTz_Rx_DMA_Channel);DMA_InitStructure.PeriphAddr = USARTz_DR_Base;DMA_InitStructure.MemAddr    = (uint32_t)RxBuffer2;DMA_InitStructure.Direction  = DMA_DIR_PERIPH_SRC;DMA_InitStructure.BufSize    = TxBufferSize1;DMA_Init(USARTz_Rx_DMA_Channel, &DMA_InitStructure);
}void func_init_uart4()
{//RCC_Configuration/* Enable GPIO clock */GPIO_APBxClkCmd(USARTx_GPIO_CLK | RCC_APB2_PERIPH_AFIO, ENABLE);/* Enable USARTy and USARTz Clock */USART_APBxClkCmd(USARTx_CLK, ENABLE);//GPIO_ConfigurationGPIO_InitType GPIO_InitStructure;GPIO_ConfigPinRemap(GPIO_RMP_USART1,ENABLE);/* Configure USARTx Tx as alternate function push-pull */GPIO_InitStructure.Pin        = USARTx_TxPin;GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;GPIO_InitStructure.GPIO_Mode  = GPIO_Mode_AF_PP;GPIO_Init(USARTx_GPIO, &GPIO_InitStructure);/* Configure USARTx Rx as input floating */GPIO_InitStructure.Pin       = USARTx_RxPin;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;GPIO_Init(USARTx_GPIO, &GPIO_InitStructure);GPIO_ConfigPinRemap(GPIO_RMP3_UART4, ENABLE);//uart/* USARTy and USARTz configuration ------------------------------------------------------*/USART_InitStructure.BaudRate            = 115200;USART_InitStructure.WordLength          = USART_WL_8B;USART_InitStructure.StopBits            = USART_STPB_1;USART_InitStructure.Parity              = USART_PE_NO;USART_InitStructure.HardwareFlowControl = USART_HFCTRL_NONE;USART_InitStructure.Mode                = USART_MODE_RX | USART_MODE_TX;/* Configure USARTx */USART_Init(USARTx, &USART_InitStructure);/* Enable the USARTx */USART_Enable(USARTx, ENABLE);}void print_dma()
{//    printf("TxBuffer1 = [%s]\r\n",(char*)TxBuffer1);
//    printf("TxBuffer2 = [%s]\r\n",(char*)TxBuffer2);printf("RxBuffer1 = [%s]\r\n",(char*)RxBuffer1);
//    printf("RxBuffer2 = [%s]\r\n",(char*)RxBuffer2);printf("\r\n");
}void print_uart_wait()
{if(status_wait_uart == true){status_wait_uart = false;printf("uart transfer waiting......\r\n");}
}void print_uart_wait_end()
{status_wait_uart = true;printf("end uart wait.\r\n");
}void myDMA_tx(uint8_t uart_id)
{// choose dmaDMA_Module* dma =  USARTy_Tx_DMA_Channel;uint32_t dma_flag = DMA1_FLAG_TC1;switch(uart_id){case 5:dma =  USARTy_Tx_DMA_Channel;dma_flag= DMA1_FLAG_TC1;break;case 6:dma =  USARTz_Tx_DMA_Channel;dma_flag = DMA2_FLAG_TC8;break;default:printf("use default uart5\r\n");dma =  USARTy_Tx_DMA_Channel;dma_flag = DMA1_FLAG_TC1;break;}printf("send\r\n");// tx : send uart data to other devwhile (DMA_GetFlagStatus(dma_flag, dma) == RESET){print_uart_wait();}print_uart_wait_end();}void myUart_senddata(uint8_t uart_id,uint8_t* data, uint8_t len_send)
{uint8_t * temp_value = data;uint8_t temp_len = len_send;printf("len_send = %d, strvalue = [%s]\r\n",temp_len,(char * )data);// choose uartUSART_Module* uart =  USARTy;switch(uart_id){case 5:uart = USARTy;break;case 6:uart = USARTz;break;default:printf("use default uart5\r\n");uart = USARTy;break;}int i=0;while(temp_len > i){//        printf("i = %d, value = %02x\r\n",i,*temp_value);USART_SendData(uart,*temp_value);// wait until data has sendwhile(USART_GetFlagStatus(uart,USART_FLAG_TXDE)==RESET){}i++;temp_value++;}return;
}void myUart_tx(uint8_t uart_id,uint8_t * data,uint8_t len_send)
{int len_str = strlen(data);bool str_data = len_send>=len_str;// if send overside strlen, just send strlenint len = str_data? len_str:len_send;printf("strlen = %d, send len = %d, send>strlen = %s\r\n",len_str,len_send,str_data?"true":"false");if(str_data == true){printf("send data len overside str_len.\r\n");}else{printf("send data len = %d.\r\n",len_send);}myUart_senddata(uart_id,data,len);
}void myUart_rx(uint8_t uart_id,bool rx_tx)
{USART_Module * uart = USARTy;DMA_Module * dma = USARTy_Rx_DMA_Channel;switch(uart_id){case 5:uart = USARTy;dma = USARTy_Rx_DMA_Channel;break;case 6:uart = USARTz;dma = USARTz_Rx_DMA_Channel;break;default:printf("use default uart5\r\n");uart = USARTy;break;}//    printf("receive\r\n");// rx : get uart data from other dev/* Wait until USARTy get idlef */while (USART_GetFlagStatus(uart, USART_FLAG_IDLEF) == RESET){print_uart_wait();}print_uart_wait_end();printf("uart is idlef\r\n");int dma_last = DMA_GetCurrDataCounter(USARTy_Rx_DMA_Channel);printf("dma get count =%d \r\n",dma_last);printf("has recv data len = %d\r\n",TxBufferSize2-dma_last);reset_dma_rx();
}void reset_dma_rx()
{print_dma();memset(RxBuffer1,0x00,sizeof(RxBuffer1));DMA_EnableChannel(USARTy_Rx_DMA_Channel, DISABLE);DMA_SetCurrDataCounter(USARTy_Rx_DMA_Channel,TxBufferSize1);DMA_EnableChannel(USARTy_Rx_DMA_Channel, ENABLE);// clear idlef flagUSART_ReceiveData(USARTy);
}void reset_dma_tx()
{print_dma();memset(TxBuffer1,0x00,sizeof(TxBuffer1));DMA_EnableChannel(USARTy_Rx_DMA_Channel, DISABLE);DMA_SetCurrDataCounter(USARTy_Rx_DMA_Channel,TxBufferSize1);DMA_EnableChannel(USARTy_Rx_DMA_Channel, ENABLE);// clear idlef flagUSART_ReceiveData(USARTy);
}/*** @brief  Delay function.*/
void delay(vu32 nCount)
{vu32 index = 0;for (index = (34000 * nCount); index != 0; index--){}
}/*** @}*//*** @}*/

6 结果

可以看到，串口接收工具

收到dma传输的字符串
收到通过uart函数传输的字符串
向uart5发出不定长度的数据，log中显示出来获取的数据及长度。

7 使用函数

USART_SendData：uart传输数据tx
USART_GetFlagStatus：获取uart状态，根据传入的uart和flag，返回set表示该flag已经设置，则跳出while循环

DMA_GetCurrDataCounter：获取dma剩余空间长度，用于计算当前收到了多少数据。

DMA_EnableChannel：开关dma的channel，两个dma，每个有8channel。
DMA_SetCurrDataCounter：设置当前dma的指针。
PS：收到过一次后需要开关dma，然后重新设置当前数据数。

此外，由于判断dma收到数据状态，通过判断usart的idle，空闲中断。
当判定到uart收到空闲中断，则表示uart数据传输完成。不过该状态清空需要使用到receive函数。
USART_ReceiveData：uart接收数据rx。

8 小结

本章介绍了结合uart及dma实现数据的收发，后续再结合串口屏实现功能。

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【中移芯昇】3. uart读写

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