ChibiOS Free Embedded RTOS

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/**
 * 
 * @file ChibiOS_3/myprogsNucleoF401RE/ADC2/main.c
 * 
 * @brief buttonUser on => ADC (single) conversion on PC5 pin (send on serial terminal via USB)
 * @details error at compilation with chprintf.h. It was not in ../os/hal/include
 *  and no more in ../os/various. Copy it from /os/hal/lib/streams and add to Makefile:
 * $(CHIBIOS)/os/hal/lib/streams/chprintf.c (line 105)
 *
 * In order to use the PAL driver the HAL_USE_PAL option must be enabled in halconf.h.
 * You must enable too, the ADC subsystem in halconf.h
 *
 * In mcuconf.h, set:
 * STM32_ADC_USE_ADC1       TRUE
 * STM32_SERIAL_USE_USART2    TRUE
 */ 
#include "ch.h" 
#include "hal.h" 
#include "chprintf.h"
 
/*
 * Defines for single scan conversion
 */
#define ADC_GRP1_NUM_CHANNELS   1
#define ADC_GRP1_BUF_DEPTH      2048*2*4
 
/*
 * Buffer for single conversion
 */
static adcsample_t samples1[ADC_GRP1_NUM_CHANNELS * ADC_GRP1_BUF_DEPTH];

/*
 * ADC conversion group.
 * Mode:        Linear buffer, 8 samples of 1 channel, SW triggered.
 * Channels:    IN15 = PC5 = Morpho Nucleo CN10-pin 6.
 */
static const ADCConversionGroup adcgrpcfg1 = {
  FALSE,                                 // circular buffer mode
  ADC_GRP1_NUM_CHANNELS,                 // Number of the analog channels
  NULL,                                  // Callback function (not needed here)
  NULL,                                // Error callback
  0,                                     // CR1
  ADC_CR2_SWSTART,                       // CR2
  ADC_SMPR1_SMP_AN15(ADC_SAMPLE_3),      // sample times ch10-18
  0,                                     // sample times ch0-9
  ADC_SQR1_NUM_CH(ADC_GRP1_NUM_CHANNELS),// SQR1: Conversion group sequence 13...16 + sequence length
  0,                                     // SQR2: Conversion group sequence 7...12
  ADC_SQR3_SQ1_N(ADC_CHANNEL_IN15)       // SQR3: Conversion group sequence 1...6
};
 
int main(void) { 

  halInit(); 
  chSysInit();
    
 /*
  * ADC init
  */
  palSetPadMode(GPIOC, GPIOC_PIN5, PAL_MODE_INPUT_ANALOG);
  adcStart(&ADCD1, NULL); 

  /* 
   * Activates the serial driver 2 using the driver default configuration: 
   * 38400 bauds, 8bits, 1 stop-bit, no parity 
   */ 
  sdStart(&SD2, NULL);
    
  /* 
   * Normal main() thread activity, in this demo it does nothing except 
   * sleeping in a loop and check the button state. 
   */ 
  while (TRUE) 
   { 
    if (!palReadPad(GPIOC, GPIOC_BUTTON)){       // user button pushed

/*
 * single analog conversion
 * converts ADC_GRP1_BUF_DEPTH samples and averages them
 * with ADC_GRP1_BUF_DEPTH==2048 this gives around 14 bit precision
 * even though the ADC hardware has only 12 bits internal precision
 * also at 2048 samples the 14 bit are nearly noise free, while
 * each sample is very noisy.
 * WARNING: If you average to many samples, the variable containing
 *  the sum may overflow. That means that your readings will be wrong.
 * However: With the ADC delivering a max value of 2^12, with uint32_t
 *  you can average 2^20 = 1048576 samples.
 */

  uint32_t sum=0;
  unsigned int i;

  adcConvert(&ADCD1, &adcgrpcfg1, samples1, ADC_GRP1_BUF_DEPTH);

  //prints the first measured value
  chprintf((BaseSequentialStream *)&SD2, "Measured: %d  ", samples1[0]*16);
  sum=0;
  for (i=0;i<ADC_GRP1_BUF_DEPTH;i++){
      sum += samples1[i];
  }
  //prints the averaged value with two digits precision
  chprintf((BaseSequentialStream *)&SD2, "%U\r\n", sum/(ADC_GRP1_BUF_DEPTH/16));
 }
  chThdSleepMilliseconds(500);
 }
}