DMA configuration for USART Reception in STM32L152

[Ajay Paul]

Posted on January 04, 2017 at 14:41

Hi,

I was trying to configure a DMA for receiving data continuously from USART in STM32L152 Discovery board. I am able to configure the USART TX for DMA. But when i am trying to configure the DMA for RX, even interrupt is also not coming. Can anyone suggest me how to solve this issue . I am  adding the code below.

#include 'stm32l1xx.h'

#include 'stm32l1xx_usart.h'#include 'stm32l1xx_gpio.h'#include 'stm32l1xx_rcc.h'#include 'stm32l1xx_dma.h'#define USART2_BAUDRATE                 115200  /**************************************************************************************/ void RCC_Configuration(void){  /* --------------------------- System Clocks Configuration -----------------*/  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA | RCC_AHBPeriph_DMA1, ENABLE);  RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2, ENABLE);} /**************************************************************************************/ void GPIO_Configuration(void){  GPIO_InitTypeDef GPIO_InitStructure;   /*-------------------------- GPIO Configuration ----------------------------*/  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2 | GPIO_Pin_3;  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_40MHz;  GPIO_Init(GPIOA, &GPIO_InitStructure);   /* Connect USART pins to AF */  GPIO_PinAFConfig(GPIOA, GPIO_PinSource2, GPIO_AF_USART2);  GPIO_PinAFConfig(GPIOA, GPIO_PinSource3, GPIO_AF_USART2);} /**************************************************************************************/ void USART2_Configuration(void){    USART_InitTypeDef USART_InitStructure;   USART_InitStructure.USART_BaudRate = USART2_BAUDRATE;  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(USART2, &USART_InitStructure);   USART_Cmd(USART2, ENABLE);} /**************************************************************************************/ uint8_t Buffer[]='shokam'; void DMA_Configuration(void){  DMA_InitTypeDef  DMA_InitStructure;   DMA_DeInit(DMA1_Channel7);   DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC; // Receive  DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)Buffer;  DMA_InitStructure.DMA_BufferSize = (uint16_t)sizeof(Buffer);  DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)&USART2->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_M2M = DMA_M2M_Disable;   DMA_Init(DMA1_Channel7, &DMA_InitStructure);   /* Enable the USART Rx DMA request */  USART_DMACmd(USART2, USART_DMAReq_Rx, ENABLE);   /* Enable DMA Stream Half Transfer and Transfer Complete interrupt */  DMA_ITConfig(DMA1_Channel7, DMA_IT_TC, ENABLE);   /* Enable the DMA RX Stream */  DMA_Cmd(DMA1_Channel7, ENABLE);  } /**************************************************************************************/ void DMA1_Channel7_IRQHandler(void){  /* Test on DMA Stream Transfer Complete interrupt */  if (DMA_GetITStatus(DMA1_IT_TC7))  {    /* Clear DMA Stream Transfer Complete interrupt pending bit */    DMA_ClearITPendingBit(DMA1_IT_TC7);     USART_SendData(USART2, 'C');  }   } /**************************************************************************************/ 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 = DMA1_Channel7_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();   USART2_Configuration();   DMA_Configuration();   while(1);}

[Oliver Beirne]

Posted on January 04, 2017 at 15:06

Hi

ajaypaul2008@gmial.com

I have moved your post to the

https://community.st.com/community/stm32-community/stm32-forum?sr=search&ampsearchId=ce1233ef-d5fc-48ea-b8d1-28e9854d529a&ampsearchIndex=0

which is the best place to ask any product-related STM32 questions.

Thanks

Oli

[waclawek.jan]

Posted on January 04, 2017 at 15:22

USART2_Rx is at DMA Channel 6 rather than Channel7, isn't it?

Also

- don't look at the UART registers in debugger, reading data register even in debugger clears the RXNE flag

- don't try to use interrupts and DMA at the same time, they work out of the very same RXNE flag

[Tesla DeLorean]

Posted on January 04, 2017 at 16:59

// STM32 USART2 DMA RX (Tx PA.2, Rx PA.3) STM32L152RE NUCLEO - sourcer32@gmail.com
#include 'stm32l1xx.h'
#include <string.h>
/**************************************************************************************/
void RCC_Configuration(void)
{
 /* --------------------------- System Clocks Configuration -----------------*/
 /* USART2 clock enable */
 RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2, ENABLE);
 /* GPIOA and DMA1 clock enable */
 RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA | RCC_AHBPeriph_DMA1, ENABLE);
}
/**************************************************************************************/
void GPIO_Configuration(void)
{
 GPIO_InitTypeDef GPIO_InitStructure;
 /*-------------------------- GPIO Configuration ----------------------------*/
 GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2 | GPIO_Pin_3; // PA.2 USART2_TX, PA.3 USART2_R
X 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_2MHz;
 GPIO_Init(GPIOA, &GPIO_InitStructure);
 /* Connect USART pins to AF */
 GPIO_PinAFConfig(GPIOA, GPIO_PinSource2, GPIO_AF_USART2);
 GPIO_PinAFConfig(GPIOA, GPIO_PinSource3, GPIO_AF_USART2);
}
/**************************************************************************************/
void USART2_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(USART2, &USART_InitStructure);
 USART_Cmd(USART2, ENABLE);
}
/**************************************************************************************/
uint8_t Buffer[] = 'The quick brown fox jumps over the lazy dog';
void DMA_Configuration(void)
{
 DMA_InitTypeDef DMA_InitStructure;
 DMA_DeInit(DMA1_Channel6);
 DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC; // Receive
 DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)Buffer;
 DMA_InitStructure.DMA_BufferSize = (uint16_t)sizeof(Buffer);
 DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)&USART2->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_M2M = DMA_M2M_Disable;
 DMA_Init(DMA1_Channel6, &DMA_InitStructure);
 /* Enable the USART Rx DMA request */
 USART_DMACmd(USART2, USART_DMAReq_Rx, ENABLE);
 /* Enable DMA Stream Transfer Complete interrupt */
 DMA_ITConfig(DMA1_Channel6, DMA_IT_TC, ENABLE);
 
 /* Enable the DMA RX Stream */
 DMA_Cmd(DMA1_Channel6, ENABLE);
}
/**************************************************************************************/
void DMA1_Channel6_IRQHandler(void)
{
 /* Test on DMA Stream Transfer Complete interrupt */
 if (DMA_GetITStatus(DMA1_IT_TC6))
 {
 /* Clear DMA Stream Transfer Complete interrupt pending bit */
 DMA_ClearITPendingBit(DMA1_IT_TC6);
 USART_SendData(USART2, 'C');
 }
}
/**************************************************************************************/
void NVIC_Configuration(void)
{
 NVIC_InitTypeDef NVIC_InitStructure;
 /* Configure the Priority Group to 2 bits */
 NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);
 /* Enable the USART2 RX DMA Interrupt, per RM0038 */
 NVIC_InitStructure.NVIC_IRQChannel = DMA1_Channel6_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();
 USART2_Configuration();
 DMA_Configuration();
 while(1); // Don't want to exit
}
/**************************************************************************************/
#ifdef USE_FULL_ASSERT
/**
 * @brief Reports the name of the source file and the source line number
 * where the assert_param error has occurred.
 * @param file: pointer to the source file name
 * @param line: assert_param error line source number
 * @retval None
 */
void assert_failed(uint8_t* file, uint32_t line)
{
 /* User can add his own implementation to report the file name and line number,
 ex: printf('Wrong parameters value: file %s on line %d

', file, line) */
 while (1)
 {}
}
#endif
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[Ajay Paul]

Posted on January 05, 2017 at 05:29

Thanks

Turvey.Clive.002

and

Waclawek.Jan

for the quick replay. And it is working now. But i am not able to figure out that, what is the significance of Buffer initialization? and Do I need to ensure that, the data which I am sending through uart should be same size as that of initial Buffer size??

[Tesla DeLorean]

Posted on January 06, 2017 at 22:05

You'd really want to pick a buffer that suits your needs, doing DMA RX requires some thought if you are not dealing with a constant stream of data. The case for DMA TX is a lot easier to make, and manage.

I used initialization because it is a lot easier to see in the debugger's memory viewer, and that other examples from which this was culled do both TX and RX in a loop from the same buffer, so what is received is ultimately sent out in a loop. The goal generally with the examples is to make them as simple and illustrative as possible, rather than to solve a more complex use case. If the fundamental concepts are understood they can be extended/applied to more complete systems.