main.cpp

00001 /*
00002  * Reading built-in temperature sensor of STM32F103RB chip (on a NUCLEO-F103RB board)
00003  */
00004 
00005 #include "mbed.h"
00006 
00007 /* 
00008  * STM32F103x data-sheet:
00009  * 5.3.19 Temperature sensor characteristics 
00010  * Table 50. TS characteristics, Page 80
00011  */
00012 const float         AVG_SLOPE   = 4.3E-03;      // slope (gradient) of temperature line function  [V/°C]
00013 const float         V25         = 1.43;         // sensor's output voltage at 25°C [V]
00014 const float         ADC_TO_VOLT = 3.3 / 4096;   // conversion coefficient of digital value to voltage [V] 
00015                                                 // when using 3.3V ref. voltage at 12-bit resolution (2^12 = 4096)
00016 
00017 Serial              pc(USBTX, USBRX);
00018 DigitalOut          led(PC_13);
00019 ADC_HandleTypeDef   hadc1;                      // ADC handle
00020 uint16_t            adcValue;                   // digital value of sensor
00021 float               vSense;                     // sensor's output voltage [V]
00022 float               temp;                       // sensor's temperature [°C]
00023 
00024 /* ADC1 init function */
00025 void MX_ADC1_Init(void)
00026 {
00027     ADC_ChannelConfTypeDef  sConfig;
00028 
00029     /**Common config
00030         */
00031     hadc1.Instance = ADC1;
00032     hadc1.Init.ScanConvMode = ADC_SCAN_DISABLE;
00033     hadc1.Init.ContinuousConvMode = DISABLE;
00034     hadc1.Init.DiscontinuousConvMode = DISABLE;
00035     hadc1.Init.ExternalTrigConv = ADC_SOFTWARE_START;
00036     hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
00037     hadc1.Init.NbrOfConversion = 1;
00038     HAL_ADC_Init(&hadc1);
00039 
00040     /**Configure Regular Channel
00041         */
00042     sConfig.Channel = ADC_CHANNEL_TEMPSENSOR;
00043     sConfig.Rank = 1;
00044     sConfig.SamplingTime = ADC_SAMPLETIME_239CYCLES_5;
00045     HAL_ADC_ConfigChannel(&hadc1, &sConfig);
00046 }
00047 
00048 int main()
00049 {
00050     MX_ADC1_Init();                                                 // initialize AD convertor
00051     while(HAL_ADCEx_Calibration_Start(&hadc1) != HAL_OK);           // calibrate AD convertor
00052 
00053     while(1) {        
00054         HAL_ADC_Start(&hadc1);                                      // start analog to digital conversion
00055         while(HAL_ADC_PollForConversion(&hadc1, 1000000) != HAL_OK);// wait for completing the conversion
00056         adcValue = HAL_ADC_GetValue(&hadc1);                        // read sensor's digital value
00057         vSense = adcValue * ADC_TO_VOLT;                            // convert sensor's digital value to voltage [V]
00058         /*
00059          * STM32F103xx Reference Manual:
00060          * 11.10 Temperature sensor
00061          * Reading the temperature, Page 235
00062          * Temperature (in °C) = {(V25 - Vsense) / Avg_Slope} + 25
00063          */
00064         temp = (V25 - vSense) / AVG_SLOPE + 25.0f;                  // convert sensor's output voltage to temperature [°C]
00065         pc.printf("temp = %3.1f%cC\n", temp, 176);                  // display chip's temperature [°C]
00066         led = !led;
00067         wait_ms(1000);
00068    }
00069 }