Questions regarding implementing a UART_DMA Receiver.

[randyao12345]

Posted on March 03, 2015 at 20:35

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 section2. Control the timing of DMA_Tx based on what is received DMA_RxIs 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)  {  }}

[Tesla DeLorean]

Posted on March 03, 2015 at 21:36

DMA_IT_TCIF4 should be DMA_IT_TCIF6 for Stream 6

So basically a port from a UART4 DMA TX example to USART6 TX Are you sure there are any benefits here to using DMA RX for this? Surely the simplest solution is to have a state machine, service the USART RXNE, and identify the input character(s), and queue up DMA TX response(s).

[randyao12345]

Posted on March 03, 2015 at 22:00

Thanks clive!

I almost forgot. So basically, Initiate RXNE Interrupt. During interrupt, check received data. But, how would I control when to send DMA_TX output using Rx received data? (Right now I only know how to send in a continuous loop, or send one singular right after startup)Much appreciated.

[Tesla DeLorean]

Posted on March 03, 2015 at 22:42

You'd want to queue up output buffers, and light off new ''Normal'' mode DMA transfers in the TC interrupt as the prior one completes.

I build a multi-string USART6 DMA example in this other thread.

/public/STe2ecommunities/mcu/Lists/cortex_mx_stm32/Flat.aspx?RootFolder=https://my.st.com/public/STe2ecommunities/mcu/Lists/cortex_mx_stm32/DMA%20Memory%20To%20UART5&FolderCTID=0x01200200770978C69A1141439FE559EB459D7580009C4E14902C3CDE46A77F0FFD06506F5B&currentviews=4051

// STM32 USART6 DMA TX/RX (Tx PC.6, Rx PC.7) STM32F4 Discovery - sourcer32@gmail.com
#include ''stm32f4_discovery.h''
/**************************************************************************************/
void RCC_Configuration(void)
{
/* --------------------------- System Clocks Configuration -----------------*/
/* USART6 clock enable */
RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART6, ENABLE);
/* GPIOC clock enable */
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC, ENABLE);
/* DMA2 clock enable */
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA2, ENABLE);
}
/**************************************************************************************/
void GPIO_Configuration(void)
{
GPIO_InitTypeDef GPIO_InitStructure;
/*-------------------------- GPIO Configuration ----------------------------*/
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7; // PC.6 USART6_TX, PC.7 USART6_RX
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 USART6_Configuration(void)
{
USART_InitTypeDef USART_InitStructure;
/* USARTx configuration ------------------------------------------------------*/
/* USARTx configured as follow:
- BaudRate = 115200 baud
- 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 = 115200;
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);
}
/**************************************************************************************/
// Output as a loop, received data overwrites, and subsequently outputs during next cycle
char Buffer[] = ''The quick brown fox jumps over the lazy dog

'';
void DMA_Configuration(void)
{
DMA_InitTypeDef DMA_InitStructure;
// USART6_TX DMA Channel 5, DMA2, Stream7 (alt Stream6 potential clash SDIO)
DMA_DeInit(DMA2_Stream7);
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) - 1;
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_Stream7, &DMA_InitStructure);
/* Enable the USART Tx DMA request */
USART_DMACmd(USART6, USART_DMAReq_Tx, ENABLE);
/* Enable DMA Stream Transfer Complete interrupt */
DMA_ITConfig(DMA2_Stream7, DMA_IT_TC, ENABLE);
/* Enable the DMA TX Stream */
DMA_Cmd(DMA2_Stream7, ENABLE);
// USART6_RX DMA Channel 5, DMA2, Stream1 (alt Stream2)
DMA_DeInit(DMA2_Stream1);
DMA_InitStructure.DMA_Channel = DMA_Channel_5;
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralToMemory; // Receive
DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)Buffer;
DMA_InitStructure.DMA_BufferSize = (uint16_t)sizeof(Buffer) - 1;
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_Stream1, &DMA_InitStructure);
/* Enable the USART Rx DMA request */
USART_DMACmd(USART6, USART_DMAReq_Rx, ENABLE);
/* Enable DMA Stream Transfer Complete interrupt */
DMA_ITConfig(DMA2_Stream1, DMA_IT_TC, ENABLE);
/* Enable the DMA RX Stream */
DMA_Cmd(DMA2_Stream1, ENABLE);
}
/**************************************************************************************/
void DMA2_Stream7_IRQHandler(void) // USART6_TX
{
/* Test on DMA Stream Transfer Complete interrupt */
if (DMA_GetITStatus(DMA2_Stream7, DMA_IT_TCIF7))
{
/* Clear DMA Stream Transfer Complete interrupt pending bit */
DMA_ClearITPendingBit(DMA2_Stream7, DMA_IT_TCIF7);
}
}
/**************************************************************************************/
void DMA2_Stream1_IRQHandler(void) // USART6_RX
{
/* Test on DMA Stream Transfer Complete interrupt */
if (DMA_GetITStatus(DMA2_Stream1, DMA_IT_TCIF1))
{
/* Clear DMA Stream Transfer Complete interrupt pending bit */
DMA_ClearITPendingBit(DMA2_Stream1, DMA_IT_TCIF1);
}
}
/**************************************************************************************/
void NVIC_Configuration(void)
{
NVIC_InitTypeDef NVIC_InitStructure;
/* Configure the Priority Group to 2 bits */
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);
/* Enable the USART6 TX DMA Interrupt */
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);
/* Enable the USART6 RX DMA Interrupt */
NVIC_InitStructure.NVIC_IRQChannel = DMA2_Stream1_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();
USART6_Configuration();
DMA_Configuration();
while(1); // Don't want to exit
}
/**************************************************************************************/

[randyao12345]

Posted on March 25, 2015 at 21:48

Hey Clive,

Thanks so much for the response. I currently have the RXNE interrupt, and data reading also setup, attached follows. But how exactly would you light off new DMA ''normal'' transfer? Is it by DMA_ClearITPendingBit(DMA2_Stream7, DMA_IT_TCIF7);? Clearing transfer complete interrupt and thus another normal mode starts?Appreciated.Attached RXNE interrupt code:void USART6_IRQHandler(void){    // Ignore framing/parity/error issues for now    if(USART_GetITStatus(USART6, USART_IT_RXNE) == SET)    {    if(USART_ReceiveData(USART6)==0xA1)    { //       uint16_t temp = UART4->DR; // Or USART_ReceiveData(UART4);     DMA_ClearITPendingBit(DMA2_Stream7, DMA_IT_TCIF7);     GPIOD->BSRRL = GPIO_Pin_12; //debugging only    }    }}

[Tesla DeLorean]

Posted on March 25, 2015 at 22:29

I currently have the RXNE interrupt, and data reading also setup, attached follows. But how exactly would you light off new DMA ''normal'' transfer?

The cited multi-string example should illustrate how to light off a new DMA transaction after the previous one ended. You might want to flag when it goes idle, so as to know when to start again.