MAX31856的STM32代码

由于MAX31856是一款数字温度传感器，因此它只需使用SPI接口与STM32通信。以下是一份简单的STM32代码：

#include "stm32f10x.h"
#include "spi.h"
#include "max31856.h"

#define MAX31856_CS_PIN     GPIO_Pin_4
#define MAX31856_CS_PORT    GPIOA

void MAX31856_Init(void)
{
    GPIO_InitTypeDef GPIO_InitStructure;
    SPI_InitTypeDef SPI_InitStructure;

    // Enable GPIO clock
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);

    // Enable SPI clock
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_SPI1, ENABLE);

    // Configure CS pin
    GPIO_InitStructure.GPIO_Pin = MAX31856_CS_PIN;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
    GPIO_Init(MAX31856_CS_PORT, &GPIO_InitStructure);

    // Configure SPI pins
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5 | GPIO_Pin_6 | GPIO_Pin_7;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_Init(GPIOA, &GPIO_InitStructure);

    // Configure SPI
    SPI_InitStructure.SPI_Direction = SPI_Direction_2Lines_FullDuplex;
    SPI_InitStructure.SPI_Mode = SPI_Mode_Master;
    SPI_InitStructure.SPI_DataSize = SPI_DataSize_8b;
    SPI_InitStructure.SPI_CPOL = SPI_CPOL_Low;
    SPI_InitStructure.SPI_CPHA = SPI_CPHA_1Edge;
    SPI_InitStructure.SPI_NSS = SPI_NSS_Soft;
    SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_4;
    SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;
    SPI_InitStructure.SPI_CRCPolynomial = 7;
    SPI_Init(SPI1, &SPI_InitStructure);

    // Enable SPI
    SPI_Cmd(SPI1, ENABLE);
}

uint8_t MAX31856_ReadRegister(uint8_t reg)
{
    uint8_t data;

    // Set CS low
    GPIO_ResetBits(MAX31856_CS_PORT, MAX31856_CS_PIN);

    // Send read command
    SPI_I2S_SendData(SPI1, (reg << 2) | 0x01);

    // Wait for transfer to complete
    while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_TXE) == RESET);

    // Receive data
    data = SPI_I2S_ReceiveData(SPI1);

    // Set CS high
    GPIO_SetBits(MAX31856_CS_PORT, MAX31856_CS_PIN);

    return data;
}

void MAX31856_WriteRegister(uint8_t reg, uint8_t value)
{
    // Set CS low
    GPIO_ResetBits(MAX31856_CS_PORT, MAX31856_CS_PIN);

    // Send write command
    SPI_I2S_SendData(SPI1, (reg << 2) & 0xFC);

    // Wait for transfer to complete
    while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_TXE) == RESET);

    // Send data
    SPI_I2S_SendData(SPI1, value);

    // Wait for transfer to complete
    while (SPI_I2S_GetFlagStatus(SPI1, SPI_I2S_FLAG_TXE) == RESET);

    // Set CS high
    GPIO_SetBits(MAX31856_CS_PORT, MAX31856_CS_PIN);
}

float MAX31856_ReadTemperature(void)
{
    uint8_t reg = MAX31856_REG_RTD_MSB;
    uint8_t data[4];
    int32_t rtd, ref, rtd_scaled, ref_scaled;
    float resistance, temperature;

    // Read RTD and reference data
    for (int i = 0; i < 4; i++) {
        data[i] = MAX31856_ReadRegister(reg++);
    }

    // Combine RTD and reference data
    rtd = ((int32_t)data[0] << 8) | data[1];
    ref = ((int32_t)data[2] << 8) | data[3];

    // Scale RTD and reference values
    rtd_scaled = rtd >> 1;
    ref_scaled = ref >> 1;

    // Calculate resistance
    resistance = ((float)ref_scaled / (float)32768.0) * 430.0;

    // Calculate temperature
    temperature = (resistance - 100.0) / 0.385;

    return temperature;
}

在上面的代码中，我们首先配置了GPIO和SPI，并实现了一个用于读取和写入MAX31856寄存器的函数。然后，我们实现了一个函数来读取传感器的温度值。这个函数首先读取MAX31856的RTD和参考数据，然后使用这些数据来计算温度。注意，这个函数返回的是温度值，而不是原始的RTD或参考数据。