基于STM32、HAL库的MCP3421A0T模数转换器ADC驱动程序设计

一、简介：

MCP3421A0T是Microchip公司生产的一款18位Δ-Σ模数转换器(ADC)，具有以下特点：

• 18位分辨率

• 单通道差分输入

• 可编程增益放大器(PGA)：×1, ×2, ×4, ×8

• 可选的转换速率(3.75/15/60/240SPS)

• 内部基准电压(2.048V ±0.05%)

• I²C接口(最大400kHz)

• 低功耗(连续转换模式下仅145μA)

• 工作电压范围：2.7V-5.5V

二、硬件接口：

MCP3421A0T        STM32L4xx
----------------------------
VDD        --->  3.3V
VSS        --->  GND
SCL        --->  PB6/I2C1_SCL
SDA        --->  PB7/I2C1_SDA
ADDR       --->  GND (地址0x68)

三、头文件：

#ifndef MCP3421_H
#define MCP3421_H

#include "stm32l4xx_hal.h"

#define MCP3421_ADDR 0x68 // 默认地址(ADDR接地)

// 增益设置
typedef enum {
    MCP3421_GAIN_X1 = 0x00,
    MCP3421_GAIN_X2 = 0x01,
    MCP3421_GAIN_X4 = 0x02,
    MCP3421_GAIN_X8 = 0x03
} MCP3421_Gain;

// 采样率设置
typedef enum {
    MCP3421_SPS_240 = 0x00,
    MCP3421_SPS_60 = 0x01,
    MCP3421_SPS_15 = 0x02,
    MCP3421_SPS_3_75 = 0x03
} MCP3421_SampleRate;

// 转换模式
typedef enum {
    MCP3421_MODE_ONESHOT = 0x00,
    MCP3421_MODE_CONTINUOUS = 0x10
} MCP3421_ConversionMode;

// 初始化状态
typedef enum {
    MCP3421_OK = 0x00,
    MCP3421_ERROR = 0x01
} MCP3421_Status;

typedef struct {
    I2C_HandleTypeDef *hi2c;
    uint8_t address;
    MCP3421_Gain gain;
    MCP3421_SampleRate sample_rate;
    MCP3421_ConversionMode mode;
} MCP3421_HandleTypeDef;

// 函数声明
MCP3421_Status MCP3421_Init(MCP3421_HandleTypeDef *hdev, I2C_HandleTypeDef *hi2c, uint8_t address);
MCP3421_Status MCP3421_StartConversion(MCP3421_HandleTypeDef *hdev);
MCP3421_Status MCP3421_ReadData(MCP3421_HandleTypeDef *hdev, int32_t *result);
MCP3421_Status MCP3421_SetConfig(MCP3421_HandleTypeDef *hdev, MCP3421_Gain gain, 
                                MCP3421_SampleRate rate, MCP3421_ConversionMode mode);

#endif // MCP3421_H

四、源文件：

#include "mcp3421.h"
#include <string.h>

/**
  * @brief  初始化MCP3421
  * @param  hdev: MCP3421句柄
  * @param  hi2c: I2C句柄
  * @param  address: 设备地址
  * @retval 初始化状态
  */
MCP3421_Status MCP3421_Init(MCP3421_HandleTypeDef *hdev, I2C_HandleTypeDef *hi2c, uint8_t address)
{
    if(hi2c == NULL)
        return MCP3421_ERROR;
    
    hdev->hi2c = hi2c;
    hdev->address = address << 1; // HAL库需要左移一位
    
    // 默认配置: 18位, 连续转换, PGA=1
    hdev->gain = MCP3421_GAIN_X1;
    hdev->sample_rate = MCP3421_SPS_3_75;
    hdev->mode = MCP3421_MODE_CONTINUOUS;
    
    // 发送配置命令
    uint8_t config = 0x80; // RDY=1(启动转换), 18位
    config |= hdev->mode;
    config |= (hdev->gain << 1);
    config |= (hdev->sample_rate << 2);
    
    if(HAL_I2C_Master_Transmit(hdev->hi2c, hdev->address, &config, 1, HAL_MAX_DELAY) != HAL_OK)
        return MCP3421_ERROR;
    
    return MCP3421_OK;
}

/**
  * @brief  启动转换
  * @param  hdev: MCP3421句柄
  * @retval 操作状态
  */
MCP3421_Status MCP3421_StartConversion(MCP3421_HandleTypeDef *hdev)
{
    uint8_t config = 0x80; // RDY=1(启动转换), 18位
    config |= hdev->mode;
    config |= (hdev->gain << 1);
    config |= (hdev->sample_rate << 2);
    
    if(HAL_I2C_Master_Transmit(hdev->hi2c, hdev->address, &config, 1, HAL_MAX_DELAY) != HAL_OK)
        return MCP3421_ERROR;
    
    return MCP3421_OK;
}

/**
  * @brief  读取转换结果
  * @param  hdev: MCP3421句柄
  * @param  result: 存储转换结果的指针
  * @retval 操作状态
  */
MCP3421_Status MCP3421_ReadData(MCP3421_HandleTypeDef *hdev, int32_t *result)
{
    uint8_t data[4] = {0};
    
    // 读取3字节数据(18位模式)
    if(HAL_I2C_Master_Receive(hdev->hi2c, hdev->address, data, 3, HAL_MAX_DELAY) != HAL_OK)
        return MCP3421_ERROR;
    
    // 检查转换是否完成(第3字节的第7位)
    if((data[2] & 0x80) == 0x80)
        return MCP3421_ERROR; // 转换未完成
    
    // 组合18位数据
    *result = ((int32_t)data[0] << 16) | ((int32_t)data[1] << 8) | data[2];
    
    // 符号扩展
    if(*result & 0x20000) // 检查符号位(18位数据的第17位)
        *result |= 0xFFFC0000; // 符号扩展到32位
    
    return MCP3421_OK;
}

/**
  * @brief  设置MCP3421配置
  * @param  hdev: MCP3421句柄
  * @param  gain: 增益设置
  * @param  rate: 采样率设置
  * @param  mode: 转换模式
  * @retval 操作状态
  */
MCP3421_Status MCP3421_SetConfig(MCP3421_HandleTypeDef *hdev, MCP3421_Gain gain, 
                               MCP3421_SampleRate rate, MCP3421_ConversionMode mode)
{
    hdev->gain = gain;
    hdev->sample_rate = rate;
    hdev->mode = mode;
    
    uint8_t config = 0x80; // RDY=1(启动转换), 18位
    config |= hdev->mode;
    config |= (hdev->gain << 1);
    config |= (hdev->sample_rate << 2);
    
    if(HAL_I2C_Master_Transmit(hdev->hi2c, hdev->address, &config, 1, HAL_MAX_DELAY) != HAL_OK)
        return MCP3421_ERROR;
    
    return MCP3421_OK;
}

五、应用：

#include "main.h"
#include "i2c.h"
#include "mcp3421.h"

MCP3421_HandleTypeDef hmcp3421;

int main(void)
{
    HAL_Init();
    SystemClock_Config();
    MX_I2C1_Init();
    
    // 初始化MCP3421
    if(MCP3421_Init(&hmcp3421, &hi2c1, MCP3421_ADDR) != MCP3421_OK)
    {
        Error_Handler();
    }
    
    // 设置配置: 增益×8, 15SPS, 连续转换
    MCP3421_SetConfig(&hmcp3421, MCP3421_GAIN_X8, MCP3421_SPS_15, MCP3421_MODE_CONTINUOUS);
    
    while(1)
    {
        int32_t adc_value;
        float voltage;
        
        // 读取ADC值
        if(MCP3421_ReadData(&hmcp3421, &adc_value) == MCP3421_OK)
        {
            // 计算实际电压值
            // 18位模式下，LSB = 2.048V / (2^17) = 15.625μV
            // 增益×8时，LSB = 15.625μV / 8 = 1.953125μV
            voltage = (float)adc_value * 1.953125f / 1000000.0f;
            
            printf("ADC Value: %ld, Voltage: %.6f V\r\n", adc_value, voltage);
        }
        else
        {
            printf("Error reading ADC value\r\n");
        }
        
        HAL_Delay(1000);
    }
}

#include "i2c.h"

I2C_HandleTypeDef hi2c1;

void MX_I2C1_Init(void)
{
    hi2c1.Instance = I2C1;
    hi2c1.Init.Timing = 0x00707CBB; // 100kHz
    hi2c1.Init.OwnAddress1 = 0;
    hi2c1.Init.AddressingMode = I2C_ADDRESSINGMODE_7BIT;
    hi2c1.Init.DualAddressMode = I2C_DUALADDRESS_DISABLE;
    hi2c1.Init.OwnAddress2 = 0;
    hi2c1.Init.OwnAddress2Masks = I2C_OA2_NOMASK;
    hi2c1.Init.GeneralCallMode = I2C_GENERALCALL_DISABLE;
    hi2c1.Init.NoStretchMode = I2C_NOSTRETCH_DISABLE;
    if (HAL_I2C_Init(&hi2c1) != HAL_OK)
    {
        Error_Handler();
    }
    
    /** Configure Analogue filter */
    if (HAL_I2CEx_ConfigAnalogFilter(&hi2c1, I2C_ANALOGFILTER_ENABLE) != HAL_OK)
    {
        Error_Handler();
    }
    
    /** Configure Digital filter */
    if (HAL_I2CEx_ConfigDigitalFilter(&hi2c1, 0) != HAL_OK)
    {
        Error_Handler();
    }
}

void HAL_I2C_MspInit(I2C_HandleTypeDef* i2cHandle)
{
    GPIO_InitTypeDef GPIO_InitStruct = {0};
    if(i2cHandle->Instance==I2C1)
    {
        __HAL_RCC_GPIOB_CLK_ENABLE();
        __HAL_RCC_I2C1_CLK_ENABLE();
        
        /**I2C1 GPIO Configuration    
        PB6     ------> I2C1_SCL
        PB7     ------> I2C1_SDA 
        */
        GPIO_InitStruct.Pin = GPIO_PIN_6|GPIO_PIN_7;
        GPIO_InitStruct.Mode = GPIO_MODE_AF_OD;
        GPIO_InitStruct.Pull = GPIO_PULLUP;
        GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
        GPIO_InitStruct.Alternate = GPIO_AF4_I2C1;
        HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);
    }
}