STM32-Thermistors-NTC-main.c

/* Includes ------------------------------------------------------------------*/
#include "main.h"

/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include <stdio.h>
#include <math.h>
#include <string.h>

/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */
#define NUMSAMPLES 5                  //Number of ADC samples to average for better measurement accuracy
#define SERIESRESISTOR 10000          //Value of the series resistor in ohms
#define THERMISTORNOMINAL 10000       //Nominal resistance of the thermistor at 25°C in ohms
#define TEMPERATURENOMINAL 25           //Nominal temperature for the thermistor resistance in degrees Celsius
#define BCOEFFICIENT 3950              //Beta coefficient of the thermistor, typically between 3000 and 4000
/* USER CODE END PD */

/* Private variables ---------------------------------------------------------*/
ADC_HandleTypeDef hadc1;
UART_HandleTypeDef huart1;

/* USER CODE BEGIN PV */
char buffer[50];                  //Buffer for UART transmission
float samples[NUMSAMPLES];          //Array to store ADC sample values
float average = 0;               //Variable to store the average of ADC samples
float steinhart;                   //Variable to store the calculated temperature in Celsius
uint8_t i;                       //Loop counter for sampling
/* USER CODE END PV */

/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_ADC1_Init(void);
static void MX_USART1_UART_Init(void);
/* USER CODE BEGIN PFP */

int main(void)
{
  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();
  /* Configure the system clock */
  SystemClock_Config();
  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  MX_ADC1_Init();
  MX_USART1_UART_Init();

  /* USER CODE BEGIN WHILE */
  while (1)
  {
    /* USER CODE END WHILE */
    /* USER CODE BEGIN 3 */
      average = 0;  //Clear previous average value to ensure correct calculation for the new set of samples

      //Collect multiple ADC samples and store them in the array
      for (i = 0; i < NUMSAMPLES; i++) {
          HAL_ADC_Start(&hadc1);                              //Start the ADC conversion
          HAL_ADC_PollForConversion(&hadc1, HAL_MAX_DELAY);   //Wait for the conversion to complete
          samples[i] = HAL_ADC_GetValue(&hadc1);              //Read the ADC conversion result
          HAL_Delay(10);                                      //Delay between samples to stabilize the ADC readings
      }
    
      //Compute the average of the collected ADC samples
      for (i = 0; i < NUMSAMPLES; i++) {
          average += samples[i];  //Sum up all the ADC sample values
      }
      average /= NUMSAMPLES;  //Calculate the average of the ADC samples
      sprintf(buffer, "Average analog reading %.2f \r\n", average);  // Format the average reading for UART output
      HAL_UART_Transmit(&huart1, (uint8_t*)buffer, strlen(buffer), HAL_MAX_DELAY);  //Transmit the average reading via UART
    
      //Convert the average ADC reading to thermistor resistance and calculate temperature
      if (average > 0) {  // Ensure the average is not zero to avoid division errors
          average = 4094 / average - 1;  // Convert ADC reading to resistance using 12-bit ADC resolution
          average = SERIESRESISTOR / average;  // Calculate the thermistor resistance
    
          sprintf(buffer, "Thermistor resistance %.2f \r\n", average);  // Format the resistance value for UART output
          HAL_UART_Transmit(&huart1, (uint8_t*)buffer, strlen(buffer), HAL_MAX_DELAY);  // Transmit the resistance value via UART
    
          // Apply the Steinhart-Hart equation to convert resistance to temperature
          steinhart = average / THERMISTORNOMINAL;  //Compute the ratio of thermistor resistance to nominal resistance
          steinhart = log(steinhart);  //Compute the natural logarithm of the resistance ratio
          steinhart /= BCOEFFICIENT;  //Divide by the thermistor's Beta coefficient
          steinhart += 1.0 / (TEMPERATURENOMINAL + 273.15);  //Add the reciprocal of the nominal temperature in Kelvin
          steinhart = 1.0 / steinhart;  //Compute the reciprocal to get the temperature in Kelvin
          steinhart -= 273.15;  //Convert the temperature from Kelvin to Celsius
    
          sprintf(buffer, "Temperature: %.2f *C\r\n", steinhart);  // Format the temperature value for UART output
          HAL_UART_Transmit(&huart1, (uint8_t*)buffer, strlen(buffer), HAL_MAX_DELAY);  // Transmit the temperature value via UART
      } else {
          sprintf(buffer, "Error: Invalid ADC reading\r\n");  // Handle invalid ADC reading (e.g., division by zero)
          HAL_UART_Transmit(&huart1, (uint8_t*)buffer, strlen(buffer), HAL_MAX_DELAY);  // Transmit the error message via UART
      }
    
      HAL_Delay(1000);  // Wait for 1 second before repeating the loop

  }
  /* USER CODE END 3 */
}