市面上常见的模拟温度传感器有TI的LM35系列等。MCP9701是Microchip公司推出的相似的模拟温度传感器,管脚兼容LM35,都是三个管脚: 一个Vs, 一个GND, 一个Vout温度模拟电压输出。MCP9701相比于LM35,采用热敏二极管而非热敏电阻方式实现,自身发热量更低,因此测温更稳定些。



这里采用STM32G030J6M6芯片,采用STM32CUBEIDE开发环境,实现对MCP9701温度传感器的模拟数据读取。

STM32在读取MCP9701的模拟数据时只用到一个ADC管脚,但还需要读取内部的Vrefint管脚的电压值,从而算得当时的供电电压值,对读取到的信号ADC值进行校准,所以也需要用多通道ADC方式。
这里的ADC读取采用非中断非DMA的轮询方式,这种方式的实现有三种:
首先建立初始工程,配置时钟系统,串口和用于ADC采样的管脚:

配置USART1为通讯异步串口,采用115200波特率,其余采用默认参数:

配置ADC管脚:

ADC参数配置里,配置为多通道有两种方式,一种是选择部分可配,一种是选择全部可配,区别是选择部分可配,则扫描方向只可以选前向和后向,而顺序则是按照通道标号,需要注意通道标号是库文件里的标号顺序,不是配置界面里面的顺序,如这里配置Vrefint和IN8通道, Vrefint在IN8之前:

而实际的前向扫描顺序是先扫描IN8,再扫描Vrefint,因为在库文件里Vrefint通道的标号在IN8通道的标号之后:

配置ADC参数(二选一方式):


配置ADC参数(二选一方式):

此时因为通道数是默认1,所以扫描转换模式不能使能,要先调整通道数并配置通道扫描顺序,这个情况下可以任意编排扫描顺序,没有前向扫描和后向扫描的概念了:

扫描转换模式也就使能了

保存并生成初始工程代码:

设计的ADC采样函数为:
#define SampleTimes 1000
uint32_t ADC_Vrefint, ADC_IN8;
uint32_t ADC_IN8_SUM;
uint32_t ADC_IN8_AVG;
void PY_ADC_SCAN_CHANNELS(void)
{
uint16_t i_VDD_CALI = (*((uint16_t *)(0x1FFF75AA)))*3/3.3;
uint32_t i = 0;
ADC_Vrefint=0; ADC_IN8=0;
ADC_IN8_SUM=0;
HAL_ADCEx_Calibration_Start(&hadc1); // Calibrate ADC
while(i<SampleTimes)
{
HAL_ADC_Start(&hadc1); // Start conversion
HAL_ADC_PollForConversion(&hadc1,0x2700);
ADC_IN8 = HAL_ADC_GetValue(&hadc1); //IN8
HAL_ADC_Start(&hadc1); // Start conversion
HAL_ADC_PollForConversion(&hadc1,0x2700);
ADC_Vrefint = HAL_ADC_GetValue(&hadc1); //Vrefint
HAL_ADC_Stop(&hadc1);
ADC_IN8 =(uint32_t)(ADC_IN8*(((double)i_VDD_CALI)/ADC_Vrefint)); //Correct through real-time voltage
ADC_IN8_SUM += ADC_IN8;
i++;
}
/*Compute average value*/
ADC_IN8_AVG = ADC_IN8_SUM / SampleTimes;
}
其中SampleTimes是进行采样平均的次数,
i_VDD_CALI读取的地址来自于datasheet里,要根据datasheet里的介绍,出厂时是在什么条件下测试写入的值,然后在应用时读出来,和实时值进行对比,从而对实时供电电压进行识别,用于ADC读取的校准。

完整的工程代码:
/* USER CODE BEGIN Header */
/**
******************************************************************************
* @file : main.c
* @brief : Main program body
******************************************************************************
* @attention
*
* Copyright (c) 2022 STMicroelectronics.
* All rights reserved.
*
* This software is licensed under terms that can be found in the LICENSE file
* in the root directory of this software component.
* If no LICENSE file comes with this software, it is provided AS-IS.
*
******************************************************************************
**/
/* USER CODE END Header */
/* Includes ------------------------------------------------------------------*/
#include "main.h"
/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
/* USER CODE END Includes */
/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */
/* USER CODE END PTD */
/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */
__IO float usDelayBase;
void PY_usDelayTest(void)
{
__IO uint32_t firstms, secondms;
__IO uint32_t counter = 0;
firstms = HAL_GetTick()+1;
secondms = firstms+1;
while(uwTick!=firstms) ;
while(uwTick!=secondms) counter++;
usDelayBase = ((float)counter)/1000;
}
void PY_Delay_us_t(uint32_t Delay)
{
__IO uint32_t delayReg;
__IO uint32_t usNum = (uint32_t)(Delay*usDelayBase);
delayReg = 0;
while(delayReg!=usNum) delayReg++;
}
void PY_usDelayOptimize(void)
{
__IO uint32_t firstms, secondms;
__IO float coe = 1.0;
firstms = HAL_GetTick();
PY_Delay_us_t(1000000) ;
secondms = HAL_GetTick();
coe = ((float)1000)/(secondms-firstms);
usDelayBase = coe*usDelayBase;
}
void PY_Delay_us(uint32_t Delay)
{
__IO uint32_t delayReg;
__IO uint32_t msNum = Delay/1000;
__IO uint32_t usNum = (uint32_t)((Delay%1000)*usDelayBase);
if(msNum>0) HAL_Delay(msNum);
delayReg = 0;
while(delayReg!=usNum) delayReg++;
}
/* USER CODE END PD */
/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */
/* USER CODE END PM */
/* Private variables ---------------------------------------------------------*/
ADC_HandleTypeDef hadc1;
UART_HandleTypeDef huart1;
/* USER CODE BEGIN PV */
#define SampleTimes 1000
uint32_t ADC_Vrefint, ADC_IN8;
uint32_t ADC_IN8_SUM;
uint32_t ADC_IN8_AVG;
void PY_ADC_SCAN_CHANNELS(void)
{
uint16_t i_VDD_CALI = (*((uint16_t *)(0x1FFF75AA)))*3/3.3;
uint32_t i = 0;
ADC_Vrefint=0; ADC_IN8=0;
ADC_IN8_SUM=0;
HAL_ADCEx_Calibration_Start(&hadc1); // Calibrate ADC
while(i<SampleTimes)
{
HAL_ADC_Start(&hadc1); // Start conversion
HAL_ADC_PollForConversion(&hadc1,0x2700);
ADC_IN8 = HAL_ADC_GetValue(&hadc1); //IN8
HAL_ADC_Start(&hadc1); // Start conversion
HAL_ADC_PollForConversion(&hadc1,0x2700);
ADC_Vrefint = HAL_ADC_GetValue(&hadc1); //Vrefint
HAL_ADC_Stop(&hadc1);
ADC_IN8 =(uint32_t)(ADC_IN8*(((double)i_VDD_CALI)/ADC_Vrefint)); //Correct through real-time voltage
ADC_IN8_SUM += ADC_IN8;
i++;
}
/*Compute average value*/
ADC_IN8_AVG = ADC_IN8_SUM / SampleTimes;
}
/* USER CODE END PV */
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_USART1_UART_Init(void);
static void MX_ADC1_Init(void);
/* USER CODE BEGIN PFP */
/* USER CODE END PFP */
/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
/* USER CODE END 0 */
/**
* @brief The application entry point.
* @retval int
*/
int main(void)
{
/* USER CODE BEGIN 1 */
/* USER CODE END 1 */
/* MCU Configuration--------------------------------------------------------*/
/* Reset of all peripherals, Initializes the Flash interface and the Systick. */
HAL_Init();
/* USER CODE BEGIN Init */
/* USER CODE END Init */
/* Configure the system clock */
SystemClock_Config();
/* USER CODE BEGIN SysInit */
/* USER CODE END SysInit */
/* Initialize all configured peripherals */
MX_GPIO_Init();
MX_USART1_UART_Init();
MX_ADC1_Init();
/* USER CODE BEGIN 2 */
PY_usDelayTest();
PY_usDelayOptimize();
/* USER CODE END 2 */
/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{
PY_ADC_SCAN_CHANNELS();
HAL_UART_Transmit(&huart1, &ADC_IN8_AVG, 4, 2700);
PY_Delay_us_t(1000000);
//Temperature (degree Celsius) = ((ADC_IN8_AVG*3.3/4096)-0.4)/0.019
/* USER CODE END WHILE */
/* USER CODE BEGIN 3 */
}
/* USER CODE END 3 */
}
/**
* @brief System Clock Configuration
* @retval None
*/
void SystemClock_Config(void)
{
RCC_OscInitTypeDef RCC_OscInitStruct = {0};
RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
/** Configure the main internal regulator output voltage
*/
HAL_PWREx_ControlVoltageScaling(PWR_REGULATOR_VOLTAGE_SCALE1);
/** Initializes the RCC Oscillators according to the specified parameters
* in the RCC_OscInitTypeDef structure.
*/
RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
RCC_OscInitStruct.HSIState = RCC_HSI_ON;
RCC_OscInitStruct.HSIDiv = RCC_HSI_DIV1;
RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;
RCC_OscInitStruct.PLL.PLLM = RCC_PLLM_DIV1;
RCC_OscInitStruct.PLL.PLLN = 8;
RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
RCC_OscInitStruct.PLL.PLLR = RCC_PLLR_DIV2;
if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
{
Error_Handler();
}
/** Initializes the CPU, AHB and APB buses clocks
*/
RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
|RCC_CLOCKTYPE_PCLK1;
RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK)
{
Error_Handler();
}
}
/**
* @brief ADC1 Initialization Function
* @param None
* @retval None
*/
static void MX_ADC1_Init(void)
{
/* USER CODE BEGIN ADC1_Init 0 */
/* USER CODE END ADC1_Init 0 */
ADC_ChannelConfTypeDef sConfig = {0};
/* USER CODE BEGIN ADC1_Init 1 */
/* USER CODE END ADC1_Init 1 */
/** Configure the global features of the ADC (Clock, Resolution, Data Alignment and number of conversion)
*/
hadc1.Instance = ADC1;
hadc1.Init.ClockPrescaler = ADC_CLOCK_ASYNC_DIV6;
hadc1.Init.Resolution = ADC_RESOLUTION_12B;
hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
hadc1.Init.ScanConvMode = ADC_SCAN_SEQ_FIXED;
hadc1.Init.EOCSelection = ADC_EOC_SINGLE_CONV;
hadc1.Init.LowPowerAutoWait = DISABLE;
hadc1.Init.LowPowerAutoPowerOff = DISABLE;
hadc1.Init.ContinuousConvMode = ENABLE;
hadc1.Init.NbrOfConversion = 1;
hadc1.Init.DiscontinuousConvMode = DISABLE;
hadc1.Init.ExternalTrigConv = ADC_SOFTWARE_START;
hadc1.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;
hadc1.Init.DMAContinuousRequests = DISABLE;
hadc1.Init.Overrun = ADC_OVR_DATA_PRESERVED;
hadc1.Init.SamplingTimeCommon1 = ADC_SAMPLETIME_1CYCLE_5;
hadc1.Init.OversamplingMode = DISABLE;
hadc1.Init.TriggerFrequencyMode = ADC_TRIGGER_FREQ_HIGH;
if (HAL_ADC_Init(&hadc1) != HAL_OK)
{
Error_Handler();
}
/** Configure Regular Channel
*/
sConfig.Channel = ADC_CHANNEL_VREFINT;
sConfig.Rank = ADC_RANK_CHANNEL_NUMBER;
if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
{
Error_Handler();
}
/** Configure Regular Channel
*/
sConfig.Channel = ADC_CHANNEL_8;
if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
{
Error_Handler();
}
/* USER CODE BEGIN ADC1_Init 2 */
/* USER CODE END ADC1_Init 2 */
}
/**
* @brief USART1 Initialization Function
* @param None
* @retval None
*/
static void MX_USART1_UART_Init(void)
{
/* USER CODE BEGIN USART1_Init 0 */
/* USER CODE END USART1_Init 0 */
/* USER CODE BEGIN USART1_Init 1 */
/* USER CODE END USART1_Init 1 */
huart1.Instance = USART1;
huart1.Init.BaudRate = 115200;
huart1.Init.WordLength = UART_WORDLENGTH_8B;
huart1.Init.StopBits = UART_STOPBITS_1;
huart1.Init.Parity = UART_PARITY_NONE;
huart1.Init.Mode = UART_MODE_TX_RX;
huart1.Init.HwFlowCtl = UART_HWCONTROL_NONE;
huart1.Init.OverSampling = UART_OVERSAMPLING_16;
huart1.Init.OneBitSampling = UART_ONE_BIT_SAMPLE_DISABLE;
huart1.Init.ClockPrescaler = UART_PRESCALER_DIV1;
huart1.AdvancedInit.AdvFeatureInit = UART_ADVFEATURE_NO_INIT;
if (HAL_UART_Init(&huart1) != HAL_OK)
{
Error_Handler();
}
if (HAL_UARTEx_SetTxFifoThreshold(&huart1, UART_TXFIFO_THRESHOLD_1_8) != HAL_OK)
{
Error_Handler();
}
if (HAL_UARTEx_SetRxFifoThreshold(&huart1, UART_RXFIFO_THRESHOLD_1_8) != HAL_OK)
{
Error_Handler();
}
if (HAL_UARTEx_DisableFifoMode(&huart1) != HAL_OK)
{
Error_Handler();
}
/* USER CODE BEGIN USART1_Init 2 */
/* USER CODE END USART1_Init 2 */
}
/**
* @brief GPIO Initialization Function
* @param None
* @retval None
*/
static void MX_GPIO_Init(void)
{
/* GPIO Ports Clock Enable */
__HAL_RCC_GPIOB_CLK_ENABLE();
}
/* USER CODE BEGIN 4 */
/* USER CODE END 4 */
/**
* @brief This function is executed in case of error occurrence.
* @retval None
*/
void Error_Handler(void)
{
/* USER CODE BEGIN Error_Handler_Debug */
/* User can add his own implementation to report the HAL error return state */
__disable_irq();
while (1)
{
}
/* USER CODE END Error_Handler_Debug */
}
#ifdef USE_FULL_ASSERT
/**
* @brief Reports the name of the source file and the source line number
* where the assert_param error has occurred.
* @param file: pointer to the source file name
* @param line: assert_param error line source number
* @retval None
*/
void assert_failed(uint8_t *file, uint32_t line)
{
/* USER CODE BEGIN 6 */
/* User can add his own implementation to report the file name and line number,
ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
/* USER CODE END 6 */
}
#endif /* USE_FULL_ASSERT */
本范例定时将ADC采样到的温度数据串口输出:

0x0449对应十进制1097, STM32采用12位采样,数据已校准为对应3.3V供电时的值,所以对应的电压为 (1097/4096)*3.3=0.8838 。温度传感器型号为MCP9701A, 查看上面的参数信息(MCP9701的特征),可知对应的温度为 T= (0.8838-0.4)/0.0195 = 24.81摄氏度,与空调房内的温度符合。
对于模拟信号输出的温度传感器,如果传输路径长,一是可能受到干扰导致偏差,而是传输损耗导致信号电压损失,因此常用的保证可靠性方法是在最短的路径将模拟信号转换成数字信号,再进行远距离传输。这里采用8脚小封装的STM32G030J6M6将模拟温度数据转换成数字信号输出,可以作为一个小模块应用于需要连续快速读取温度的场景,相比常见的DS18B20数字温度传感器(每次读数有几百毫秒的温度转换时间)在温度读取速度上有优势。
经过实际测试分析验证,通过如下方式可以有效提高MCP模拟温度传感器输出稳定性:
减少传感器输出管脚的输出电流,即通过运算放大器如LM358B等实现单位增益放大器/跟随器,从而提供高输入阻抗接收模拟输出电压,并提供低输出阻抗模拟电压输出给STM32进行ADC采样
STM32CUBEIDE开发平台STM32G030J6M6读取MCP9701例程
STM32G030J6M6的USART1管脚和SWD接口存在共用,如果遇到SWD接口连接不上的情况,则要采用STM32的复位状态连接方式,用STM32 ST-LINK Utility或STM32CubeProgrammer进行连接和擦除后,再进行版本烧录:




另外,如果不采用硬件串口而采用软件模拟串口,则可以自由调整管脚,从而不必和SWD接口共用管脚。参考:
STM32 GPIO模拟UART串口:最简延时方式
STM32 GPIO模拟UART串口:外部时钟及TIM方式
–End–