DMA on STM32L011F4

[Archadious]

I'm trying to program an STM32L011F4 to transmit data through USART2 by way of the DMA controller.  My code compiles but the IRQ handler for DMA is never called.  Either I have not correctly initialized the DMA controller or there is another problem I am overlooking.  Can anyone provide suggestions?

//-----------------------------------------------------------------------------
#include <stdio.h>
#include "stm32l0xx.h"


//-----------------------------------------------------------------------------
#define USART_TX_PIN GPIO_PIN_2
#define DMA_BUFFER_SIZE 64
uint8_t dma_buffer[ DMA_BUFFER_SIZE ] = "String to send through USART2 by DMA!\r\n";

//-----------------------------------------------------------------------------
void SystemClock_Config(void);
void USART2_Init(void);
void DMA_Init(void);
void Start_DMA_Transmission(void);


//-----------------------------------------------------------------------------
int main( void ) {

  SystemClock_Config();   // Configure system clock
  USART2_Init();          // Initialize USART2
  DMA_Init();             // Initialize DMA

  Start_DMA_Transmission(); // Start data transmission over DMA

  while (1) { __asm__( "NOP" ); };

};  // end main


//-----------------------------------------------------------------------------
void SystemClock_Config( void ) {

  // Configure the system clock to use HSI at 16 MHz
  RCC->CR |= RCC_CR_HSION;  // Enable HSI
  while ( !( RCC->CR & RCC_CR_HSIRDY ) ){ __asm__( "NOP" ); };  // Wait for HSI

  RCC->CFGR = 0;  // System clock source is HSI
  SystemCoreClockUpdate();  // Update SystemCoreClock variable

};  // end SystemClock_Config


//-----------------------------------------------------------------------------
void USART2_Init( void ) {

  // Enable GPIOA and USART2 clocks
  RCC->IOPENR |= RCC_IOPENR_GPIOAEN;
  RCC->APB1ENR |= RCC_APB1ENR_USART2EN;

  // Configure PA2 as USART2 TX
  GPIOA->MODER &= ~GPIO_MODER_MODE2;          // Clear mode bits
  GPIOA->MODER |= GPIO_MODER_MODE2_1;         // Set PA2 to alternate function mode
  GPIOA->AFR[0] |= ( 4 << GPIO_AFRL_AFSEL2_Pos ); // Set PA2 to AF4 (USART2)

  // Configure USART2 baud rate, enable TX, enable USART
  USART2->BRR = SystemCoreClock / 9600;       // Set baud rate to 9600 (assuming 16 MHz clock)
  USART2->CR1 = USART_CR1_TE | USART_CR1_UE;  // Enable TX and USART

};  // end USART2_Init

//-----------------------------------------------------------------------------
void DMA_Init(void) {

  RCC->AHBENR |= RCC_AHBENR_DMA1EN;  // Enable DMA clock

  DMA1_Channel2->CCR &= ~DMA_CCR_EN;  // Disable channel before configuration

  DMA1_Channel2->CCR &= ~( DMA_CCR_MSIZE_0 | DMA_CCR_MSIZE_1 );  // Set size to 8 bits
  DMA1_Channel2->CCR &= ~( DMA_CCR_PSIZE_0 | DMA_CCR_PSIZE_1 );  // Set USART to 8 bits

  DMA1_Channel2->CCR =
    DMA_CCR_MINC |  // Enable memory increment
    DMA_CCR_DIR |  // Read from memory
    DMA_CCR_TEIE |  // Transfer error flag
    DMA_CCR_HTIE |  // Half transfer flag
    DMA_CCR_TCIE;  // Enable transfer complete interrupt

  // Configure DMA for USART2 TX (Channel 2)
  DMA1_Channel2->CPAR = (uint32_t)(&(USART2->TDR));  // Set peripheral address to USART2 TDR
  DMA1_Channel2->CMAR = (uint32_t)dma_buffer;    // Set memory address to dma_buffer
  DMA1_Channel2->CNDTR = sizeof(dma_buffer) - 1; // Set number of data items to transfer

  DMA1_Channel2->CCR &= ~( DMA_CCR_PL_0 | DMA_CCR_PL_1 );  // Set priority to low

  // Enable DMA interrupt in NVIC
  NVIC_SetPriority( DMA1_Channel2_3_IRQn, 0x0 );
  NVIC_EnableIRQ( DMA1_Channel2_3_IRQn );

};  // DMA_Init


//-----------------------------------------------------------------------------
void Start_DMA_Transmission( void ) {

  USART2->CR3 |= USART_CR3_DMAT;  // Enable DMA for USART2 TX

  while ( ( USART2->ISR & USART_ISR_TC ) != USART_ISR_TC ) { __asm__( "NOP" ); };
  USART2->ICR = USART_ICR_TCCF;  // Clear TC Flag

  DMA1_Channel2->CCR |= DMA_CCR_EN;  // Enable DMA Channel 2

};  // end Start_DMA_Transmission


//-----------------------------------------------------------------------------
void DMA1_Channel2_3_IRQHandler( void ) {

  if ( DMA1->ISR & DMA_ISR_TCIF2 ) {      // Check for transfer complete interrupt flag

    DMA1->IFCR = DMA_IFCR_CTCIF2;     // Clear transfer complete interrupt flag
    DMA1_Channel2->CCR &= ~DMA_CCR_EN; // Disable DMA Channel 4 after transfer

    return;

  };  // end TCIF2

};  // end DMA1_Channel2_3_IRQHandler

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[waclawek.jan]

> IRQ handler for DMA is never called.

How do you know?

Where does the PC end up, isn't it some default handler?

Read out and check/post content of the DMA registers.

Check the interrupt vector table in disasm.

Generic "interrupt does not fire" checklist here.

JW

[waclawek.jan · Accepted solution]

You have to set DMA_CSELR.C2S = 0b0100 to map the USART2_TX request to DMA1_Channel2 (your STM32 model is Cat.1, right?)

JW

[Archadious]

That was it, the code now works correctly.  Thanks for pointing out what I had overlooked.

I had read that section of the manual several times but thought it wasn't required because I was transmitting and not receiving data on the usart. 

-Archadious