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Analog Read

Basic example of reading from a single analog input

Start by setting PA0 to a single-ended ADC1 analog input.

STMCubeADC1.png

Navigate to the configuration tab for ADC1 and configure as follows:

STMCubeADC2.png

Project > Generate Code

Towards the bottom of the file adc.c, in the 'user code begin 1' section add the following function:

uint32_t analogRead()
{
  uint32_t ADCValue = 0;
  HAL_ADC_Start(&hadc1);
  if (HAL_ADC_PollForConversion(&hadc1, 1000000) == HAL_OK) {
      ADCValue = HAL_ADC_GetValue(&hadc1);
  }
  HAL_ADC_Stop(&hadc1);
  
  return ADCValue;
}

Call the function and print the result in main.c:

/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{
  sprintf(log_buffer, "ADCValue: %d\r\n", analogRead());
  debug_printf(log_buffer);
  HAL_Delay(200);
      
  HAL_GPIO_TogglePin(GPIOA, GPIO_PIN_5);
  HAL_Delay(100);
/* USER CODE END WHILE */

Compile and Upload, see the result with minicom:

minicom -b115200 -D/dev/ttyACM0

Example result:

ADCValue: 0
ADCValue: 0
ADCValue: 0
ADCValue: 0
ADCValue: 0
ADCValue: 0
ADCValue: 4038
ADCValue: 4038
ADCValue: 4037
ADCValue: 4038
ADCValue: 4037

Reading from two analog inputs

Using STM32CubeMX, configure PA1 as a single ended analog input as well and click on 'Generate Code' again.

Modify the analagRead function to include the following channel configuration section:

uint32_t analogRead(uint32_t channel)
{

  ADC_ChannelConfTypeDef sConfig;
  sConfig.Channel = channel;
  sConfig.Rank = ADC_REGULAR_RANK_1;
  sConfig.SingleDiff = ADC_SINGLE_ENDED;
  sConfig.SamplingTime = ADC_SAMPLETIME_601CYCLES_5;
  sConfig.OffsetNumber = ADC_OFFSET_NONE;
  sConfig.Offset = 0;

  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK) {
    _Error_Handler(__FILE__, __LINE__);
  }

  uint32_t ADCValue = 0;
  HAL_ADC_Start(&hadc1);
  if (HAL_ADC_PollForConversion(&hadc1, 1000000) == HAL_OK) {
      ADCValue = HAL_ADC_GetValue(&hadc1);
  }
  HAL_ADC_Stop(&hadc1);
  
  return ADCValue;
}

This configuration code is copied straight from the bottom of the MX_ADC1_Init function.

Call the modified function from main.c:

/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{
  sprintf(log_buffer, "ADCValue 1: %d\r\n", analogRead(1));
  debug_printf(log_buffer);
  HAL_Delay(200);
  
  sprintf(log_buffer, "ADCValue 2: %d\r\n", analogRead(2));
  debug_printf(log_buffer);
  HAL_Delay(200);
      
  HAL_GPIO_TogglePin(GPIOA, GPIO_PIN_5);
  HAL_Delay(100);
/* USER CODE END WHILE */

Example output with PA0 connected to ground and PA1 connected to 3.3V:

ADCValue 1: 0
ADCValue 2: 4037
ADCValue 1: 0
ADCValue 2: 4038
ADCValue 1: 0
ADCValue 2: 4037
ADCValue 1: 0
ADCValue 2: 4038
ADCValue 1: 0
ADCValue 2: 4038
ADCValue 1: 0
ADCValue 2: 4037
ADCValue 1: 0
ADCValue 2: 4037

Reading from two analog inputs sequentially with scan mode

The last example configure's, starts, reads and then stops the ADC for each channel. With scan conversion mode its possible to automatically read through a configured list of channels sequentially.

Enable 'Scan Conversion Mode' in the ADC configuration window.

Keep End of Conversion Selection on 'End of single conversion'.

STMCubeADC3.png

Remove the analogRead function from adc.c that we added in the previous examples. Replace the code in the main.c loop with:

/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{

  HAL_ADC_Start(&hadc1);
  
  if (HAL_ADC_PollForConversion(&hadc1, 1000) == HAL_OK) {
      ADCValue = HAL_ADC_GetValue(&hadc1);
      sprintf(log_buffer, "ADCValue 1: %d\r\n", ADCValue);
      debug_printf(log_buffer);
      
      ADCValue = HAL_ADC_GetValue(&hadc1);
      sprintf(log_buffer, "ADCValue 2: %d\r\n", ADCValue);
      debug_printf(log_buffer);
  }
  
  HAL_ADC_Stop(&hadc1);
  HAL_Delay(200);
      
  HAL_GPIO_TogglePin(GPIOA, GPIO_PIN_5);
  HAL_Delay(100);
/* USER CODE END WHILE */

Analog read on completion interrupt

This example replaces the polling for completed ADC conversions with an callback function called via an interrupt.

  • Enable 'Scan Conversion Mode' in the ADC configuration window.
  • Keep End of Conversion Selection on 'End of single conversion'.
  • NVIC Settings: Enable ADC1 and ADC2 interrupts.

In adc.c:

/* USER CODE BEGIN 0 */
char log_buffer[100];

/* USER CODE END 0 */

---

/* USER CODE BEGIN 1 */
void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef* hadc1)
{
  uint32_t ADCValue = HAL_ADC_GetValue(hadc1);
  sprintf(log_buffer, "ADCValue 1: %d\r\n", ADCValue);
  debug_printf(log_buffer);

  ADCValue = HAL_ADC_GetValue(hadc1);
  sprintf(log_buffer, "ADCValue 2: %d\r\n", ADCValue);
  debug_printf(log_buffer);
}
/* USER CODE END 1 */

In main.c:

/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{     
  HAL_ADC_Start_IT(&hadc1);
  HAL_GPIO_TogglePin(GPIOA, GPIO_PIN_5);
  HAL_Delay(500);
/* USER CODE END WHILE */