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Questions regarding implementing a UART_DMA Receiver.

Question asked by yao.randy.001 on Mar 3, 2015
Latest reply on Mar 25, 2015 by Clive One
Hi ST Forum,

I want to implement a DMA RS232 device (with a MAX232 transceiver), where if the master sends a certain message (e.g. 0x01), then the STM32 will send back a certain message (e.g. 0x02). I got the DMA Transmit part working, but I'm wondering how to:

1. Implement the DMA_Rx section
2. Control the timing of DMA_Tx based on what is received DMA_Rx

Is this even possible?

My DMA_Tx (working) is follows, any suggestion how to progress is strongly appreciated.

/*
 * PC6 USART6_TX
 * PC7 UART6_RX
 * Rate = 115.2k
 * Tested working 03/03/15
 */


#include "stm32f4xx_dma.h"
#include "stm32f4xx_gpio.h"
#include "stm32f4xx_usart.h"
#include "stm32f4xx_rcc.h"
#include "misc.h"
#include "semihosting.h"


#define UART_SPEED 115200 //defines 9600


//char Buffer[] = "The quick brown fox jumps over the lazy dog\r\n";
char Buffer[] = {0x01,0x02,0x03,0x04};


void RCC_Configuration(void)
{
  /* UART4 clock enable */ RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART6, ENABLE);
  /* GPIOC clock enable */ RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC, ENABLE);
  /* DMA1 clock enable */  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA2, ENABLE);
}


void GPIO_Configuration(void)
{
  GPIO_InitTypeDef GPIO_InitStructure;


  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7; // PC.10 UART4_TX, potential clash SCLK CS43L22
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_Init(GPIOC, &GPIO_InitStructure);
  /* Connect USART pins to AF */
  GPIO_PinAFConfig(GPIOC, GPIO_PinSource6, GPIO_AF_USART6);
  GPIO_PinAFConfig(GPIOC, GPIO_PinSource7, GPIO_AF_USART6);
}


void UART4_Configuration(void)
{
  USART_InitTypeDef USART_InitStructure;
  /* USARTx configured as follow:
        - BaudRate = 9600 baud, can be up to 115200
        - 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 = UART_SPEED; //9600 baud
  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(USART6, &USART_InitStructure);
  USART_Cmd(USART6, ENABLE);
}


void DMA_Configuration(void)
{
  DMA_InitTypeDef DMA_InitStructure;
  DMA_DeInit(DMA2_Stream6);
  DMA_InitStructure.DMA_Channel = DMA_Channel_5;
  DMA_InitStructure.DMA_DIR = DMA_DIR_MemoryToPeripheral; // Transmit
  DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)Buffer;
  DMA_InitStructure.DMA_BufferSize = (uint16_t)sizeof(Buffer);
  DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)&USART6->DR;
  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_FIFOMode = DMA_FIFOMode_Enable;
  DMA_InitStructure.DMA_FIFOThreshold = DMA_FIFOThreshold_Full;
  DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single;
  DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single;
  DMA_Init(DMA2_Stream6, &DMA_InitStructure);


  USART_DMACmd(USART6, USART_DMAReq_Tx, ENABLE);  /* Enable the USART Tx DMA request */
  DMA_ITConfig(DMA2_Stream6, DMA_IT_TC, ENABLE); /* Enable DMA Stream Transfer Complete interrupt */
  DMA_Cmd(DMA2_Stream6, ENABLE);                 /* Enable the DMA Tx Stream */
}


void DMA2_Stream6_IRQHandler(void)
{
  /* Test on DMA Stream Transfer Complete interrupt */
  if (DMA_GetITStatus(DMA2_Stream6, DMA_IT_TCIF4))
  {
    /* Clear DMA Stream Transfer Complete interrupt pending bit */
    DMA_ClearITPendingBit(DMA2_Stream6, DMA_IT_TCIF4);
  }
}


void NVIC_Configuration(void)
{
  NVIC_InitTypeDef NVIC_InitStructure;
  /* Configure the Priority Group to 2 bits */
  NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);
  /* Enable the UART4 RX DMA Interrupt */
  NVIC_InitStructure.NVIC_IRQChannel = DMA2_Stream6_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);
}


int main(void)
{
  RCC_Configuration();
  NVIC_Configuration();
  GPIO_Configuration();
  UART4_Configuration();
  DMA_Configuration();


  while(1)
  {


  }
}

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