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ADC via dma and USART

Question asked by ruibys.arvydas on Feb 13, 2013
Latest reply on May 13, 2013 by Clive One
Hello, i am having trouble writing code on STM32F4Discovery. my goal is to get values from ADC in continuous mode and send them to USART/UART (with DMA or without) using interrupts. so i wrote a code made out of couple examples on stm std lib and internet. but it doesn't work and i don't know why. please give me some guidelines :) 
Some code comments are not true because i changed things several times. ADC pin is PC2, using ADC3 peripheral, USART1 peripheral connected to PB6 ant PB7
/* Includes ------------------------------------------------------------------*/
#include "stm32f4xx.h"
/* Private define ------------------------------------------------------------*/
/* Private variables ---------------------------------------------------------*/
#define ADC3_DR_ADDRESS    ((uint32_t)0x4001224C)
uint8_t NbrOfDataToTransfer;
__IO uint8_t TxCounter; 
__IO uint16_t ADC3ConvertedValue = 0;
__IO uint32_t ADC3ConvertedVoltage = 0;
        void ADC3_CH12_DMA_Config(void)
  ADC_InitTypeDef       ADC_InitStructure;
  ADC_CommonInitTypeDef ADC_CommonInitStructure;
  DMA_InitTypeDef       DMA_InitStructure;
  GPIO_InitTypeDef      GPIO_InitStructure;
  /* Enable ADC3, DMA2 and GPIO clocks ****************************************/
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA2 | RCC_AHB1Periph_GPIOC, ENABLE);
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC3, ENABLE);
  /* DMA2 Stream0 channel2 configuration **************************************/
  DMA_InitStructure.DMA_Channel = DMA_Channel_2;  
  DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)ADC3_DR_ADDRESS;
  DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)&ADC3ConvertedValue;
  DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralToMemory;
  DMA_InitStructure.DMA_BufferSize = 1;
  DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
  DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Disable;
  DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
  DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
  DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
  DMA_InitStructure.DMA_Priority = DMA_Priority_High;
  DMA_InitStructure.DMA_FIFOMode = DMA_FIFOMode_Disable;         
  DMA_InitStructure.DMA_FIFOThreshold = DMA_FIFOThreshold_HalfFull;
  DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single;
  DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single;
  DMA_Init(DMA2_Stream0, &DMA_InitStructure);
  DMA_Cmd(DMA2_Stream0, ENABLE);
  /* Configure ADC3 Channel7 pin as analog input ******************************/
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL ;
  GPIO_Init(GPIOC, &GPIO_InitStructure);
  /* ADC Common Init **********************************************************/
  ADC_CommonInitStructure.ADC_Mode = ADC_Mode_Independent;
  ADC_CommonInitStructure.ADC_Prescaler = ADC_Prescaler_Div2;
  ADC_CommonInitStructure.ADC_DMAAccessMode = ADC_DMAAccessMode_Disabled;
  ADC_CommonInitStructure.ADC_TwoSamplingDelay = ADC_TwoSamplingDelay_5Cycles;
  /* ADC3 Init ****************************************************************/
  ADC_InitStructure.ADC_Resolution = ADC_Resolution_12b;
  ADC_InitStructure.ADC_ScanConvMode = DISABLE;
  ADC_InitStructure.ADC_ContinuousConvMode = ENABLE;
  ADC_InitStructure.ADC_ExternalTrigConvEdge = ADC_ExternalTrigConvEdge_None;
  ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_T1_CC1;
  ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
  ADC_InitStructure.ADC_NbrOfConversion = 1;
  ADC_Init(ADC3, &ADC_InitStructure);
  /* ADC3 regular channel7 configuration *************************************/
  ADC_RegularChannelConfig(ADC3, ADC_Channel_12, 1, ADC_SampleTime_3Cycles);
 /* Enable DMA request after last transfer (Single-ADC mode) */
  ADC_DMARequestAfterLastTransferCmd(ADC3, ENABLE);
  /* Enable ADC3 DMA */
  /* Enable ADC3 */
    void init_USART1(uint32_t baudrate) 
        USART_InitTypeDef USART_InitStruct;
        GPIO_InitTypeDef GPIO_InitStruct; // this is for the GPIO pins used as TX and RX
        /* enable APB2 peripheral clock for USART1 
     * note that only USART1 and USART6 are connected to APB2
     * the other USARTs are connected to APB1
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);
        /* enable the peripheral clock for the pins used by 
     * USART1, PB6 for TX and PB7 for RX
    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);
        /* This sequence sets up the TX and RX pins 
     * so they work correctly with the USART1 peripheral
    GPIO_InitStruct.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7; // Pins 6 (TX) and 7 (RX) are used
    GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF;           // the pins are configured as alternate function so the USART peripheral has access to them
    GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;      // this defines the IO speed and has nothing to do with the baudrate!
    GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;         // this defines the output type as push pull mode (as opposed to open drain)
    GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_UP;           // this activates the pullup resistors on the IO pins
    GPIO_Init(GPIOB, &GPIO_InitStruct);                 // now all the values are passed to the GPIO_Init() function which sets the GPIO registers
/* The RX and TX pins are now connected to their AF
     * so that the USART1 can take over control of the 
     * pins
    GPIO_PinAFConfig(GPIOB, GPIO_PinSource6, GPIO_AF_USART1); //
    GPIO_PinAFConfig(GPIOB, GPIO_PinSource7, GPIO_AF_USART1);
        /* Now the USART_InitStruct is used to define the 
     * properties of USART1 
  USART_InitStruct.USART_BaudRate = baudrate;
  USART_InitStruct.USART_WordLength = USART_WordLength_8b;
  USART_InitStruct.USART_StopBits = USART_StopBits_1;
  USART_InitStruct.USART_Parity = USART_Parity_No;
  USART_InitStruct.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
  USART_InitStruct.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;
  USART_Init(USART1, &USART_InitStruct);
  /* Enable the EVAL_USART1 Transmit interrupt: this interrupt is generated when the 
     EVAL_USART1 transmit data register is empty */  
    USART_Cmd(USART1, ENABLE);// finally this enables the complete USART1 peripheral
    void NVIC_Config(void)
  NVIC_InitTypeDef NVIC_InitStructure;
  /* Enable the USARTx Interrupt */
  NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
int main(void)
  while (1)
        ADC3ConvertedVoltage = ADC3ConvertedValue *3300/0xFFF;
        USART_SendData(USART1, ADC3ConvertedVoltage);
    // this is the interrupt request handler (IRQ) for ALL USART1 interrupts
void USART1_IRQHandler(void)
  /* Wait until EVAL_USART1 send the TxBuffer */
  while(TxCounter < NbrOfDataToTransfer)
  /* The software must wait until TC=1. The TC flag remains cleared during all data
     transfers and it is set by hardware at the last frame’s end of transmission*/
  while (USART_GetFlagStatus(USART1, USART_FLAG_TC) == RESET)