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STM32F4 getting values from buffer

Question asked by stone.jorge on Jul 1, 2015
Latest reply on Jul 1, 2015 by Clive One
Hi, I wanted to personalize this code I found to fill half a buffer and then process the data while the second half of the buffer continues to fill. To understand how this works I modified the code so it turns on a LED if the first value stored in the buffer is higher than 2500 mV. I think I don't know how to get data from the buffer... Need help.

Here is the code:
// STM32 ADC Sample @ 200 KHz (PC.1) STM32F4 Discovery - sourcer32@gmail.com
 
// Assumptions per system_stm32f4xx.c CPU @ 168 MHz, APB2 @ 84 MHz (/2), APB1 @ 42 MHz (/4)
 
 
#include "stm32f4xx.h"
#include "stm32f4xx_rcc.h"
#include "stm32f4xx_gpio.h"
#include "stm32f4xx_adc.h"
#include "stm32f4xx_dma.h"
#include "stm32f4_discovery.h"
#include "stm32f4xx_tim.h"
 
/**************************************************************************************/
 
void RCC_Configuration(void)
{
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA2, ENABLE);
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC, ENABLE);
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1, ENABLE);
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);
}
 
/**************************************************************************************/
 
void GPIO_Configuration(void)
{
  GPIO_InitTypeDef GPIO_InitStructure;
 
  /* ADC Channel 11 -> PC1
  */
 
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL ;
  GPIO_Init(GPIOC, &GPIO_InitStructure);
}
 
/**************************************************************************************/
 
void ADC_Configuration(void)
{
  ADC_CommonInitTypeDef ADC_CommonInitStructure;
  ADC_InitTypeDef ADC_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;
  ADC_CommonInit(&ADC_CommonInitStructure);
 
  ADC_InitStructure.ADC_Resolution = ADC_Resolution_12b;
  ADC_InitStructure.ADC_ScanConvMode = DISABLE; // 1 Channel
  ADC_InitStructure.ADC_ContinuousConvMode = DISABLE; // Conversions Triggered
  ADC_InitStructure.ADC_ExternalTrigConvEdge = ADC_ExternalTrigConvEdge_Rising;
  ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_T2_TRGO;
  ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
  ADC_InitStructure.ADC_NbrOfConversion = 1;
  ADC_Init(ADC1, &ADC_InitStructure);
 
  /* ADC1 regular channel 11 configuration */
  ADC_RegularChannelConfig(ADC1, ADC_Channel_11, 1, ADC_SampleTime_15Cycles); // PC1
 
  /* Enable DMA request after last transfer (Single-ADC mode) */
  ADC_DMARequestAfterLastTransferCmd(ADC1, ENABLE);
 
  /* Enable ADC1 DMA */
  ADC_DMACmd(ADC1, ENABLE);
 
  /* Enable ADC1 */
  ADC_Cmd(ADC1, ENABLE);
}
 
/**************************************************************************************/
 
#define BUFFERSIZE 400 // 200KHz x2 HT/TC at 1KHz
 
__IO uint16_t ADCConvertedValues[BUFFERSIZE];
 
static void DMA_Configuration(void)
{
  DMA_InitTypeDef DMA_InitStructure;
 
  DMA_InitStructure.DMA_Channel = DMA_Channel_0;
  DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)&ADCConvertedValues[0];
  DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)&ADC1->DR;
  DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralToMemory;
  DMA_InitStructure.DMA_BufferSize = BUFFERSIZE; // Count of 16-bit words
  DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
  DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
  DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
  DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
  DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;
  DMA_InitStructure.DMA_Priority = DMA_Priority_High;
  DMA_InitStructure.DMA_FIFOMode = DMA_FIFOMode_Enable;
  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);
 
  /* Enable DMA Stream Half / Transfer Complete interrupt */
  DMA_ITConfig(DMA2_Stream0, DMA_IT_TC | DMA_IT_HT, ENABLE);
 
  /* DMA2_Stream0 enable */
  DMA_Cmd(DMA2_Stream0, ENABLE);
}
 
/**************************************************************************************/
 
void TIM2_Configuration(void)
{
  TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
 
  /* Time base configuration */
  TIM_TimeBaseStructInit(&TIM_TimeBaseStructure);
  TIM_TimeBaseStructure.TIM_Period = (84000000 / 200000) - 1; // 200 KHz, from 84 MHz TIM2CLK (ie APB1 = HCLK/4, TIM2CLK = HCLK/2)
  TIM_TimeBaseStructure.TIM_Prescaler = 0;
  TIM_TimeBaseStructure.TIM_ClockDivision = 0;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
  TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);
 
  /* TIM2 TRGO selection */
  TIM_SelectOutputTrigger(TIM2, TIM_TRGOSource_Update); // ADC_ExternalTrigConv_T2_TRGO
 
  /* TIM2 enable counter */
  TIM_Cmd(TIM2, ENABLE);
}
 
/**************************************************************************************/
 
void NVIC_Configuration(void)
{
  NVIC_InitTypeDef NVIC_InitStructure;
 
  /* Enable the DMA Stream IRQ Channel */
  NVIC_InitStructure.NVIC_IRQChannel = DMA2_Stream0_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);
}
 
/**************************************************************************************/
 
void DMA2_Stream0_IRQHandler(void) // Called at 1 KHz for 200 KHz sample rate, LED Toggles at 500 Hz
{
  /* Test on DMA Stream Half Transfer interrupt */
  if(DMA_GetITStatus(DMA2_Stream0, DMA_IT_HTIF0))
  {
    /* Clear DMA Stream Half Transfer interrupt pending bit */
    DMA_ClearITPendingBit(DMA2_Stream0, DMA_IT_HTIF0);
 
    /* Turn LED3 off: Half Transfer */
    STM_EVAL_LEDOff(LED3);
 
    // Add code here to process first half of buffer (ping)
    int a;
    double valueinmV;
 
      a=ADCConvertedValues[0];
      valueinmV = (a*3300)/4095;
      if(valueinmV>2500)
      {
          STM_EVAL_LEDOn(LED5);
      }
      else
      {
          STM_EVAL_LEDOff(LED5);
    }
 
  }
 
  /* Test on DMA Stream Transfer Complete interrupt */
  if(DMA_GetITStatus(DMA2_Stream0, DMA_IT_TCIF0))
  {
    /* Clear DMA Stream Transfer Complete interrupt pending bit */
    DMA_ClearITPendingBit(DMA2_Stream0, DMA_IT_TCIF0);
 
    /* Turn LED3 on: End of Transfer */
    STM_EVAL_LEDOn(LED3);
 
 
    // Add code here to process second half of buffer (pong)
 
  }
}
void ClockSetUp(void) {
    /* Initialize system */
    SystemInit();
    RCC_DeInit();
    /* PLL Setup */
    RCC_HSEConfig(RCC_HSE_ON);
    RCC_WaitForHSEStartUp();
    RCC_PLLConfig(RCC_PLLSource_HSE,5,210,2,4);
    RCC_PLLCmd(ENABLE);
    while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY) != SET);
    RCC_HCLKConfig(RCC_SYSCLK_Div1);
    RCC_PCLK1Config(RCC_HCLK_Div4);
    RCC_PCLK2Config(RCC_HCLK_Div2);
    RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);
}
/**************************************************************************************/
 
 
int main(void)
{
 
  RCC_Configuration();
 
  GPIO_Configuration();
 
  NVIC_Configuration();
 
  TIM2_Configuration();
 
  DMA_Configuration();
 
  ADC_Configuration();
 
  ClockSetUp();
 
  STM_EVAL_LEDInit(LED3); /* Configure LEDs to monitor program status */
 
  STM_EVAL_LEDInit(LED4);
 
  STM_EVAL_LEDOn(LED3); /* Turn LED3 on, 500 Hz means it working */
 
  /* Start ADC1 Software Conversion */
  ADC_SoftwareStartConv(ADC1);
 
while(1){
}
}

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