stm32用软件iic读取ltc2990的温度值

以下是使用STM32的软件IIC读取LTC2990温度值的示例代码：

#include "stm32f4xx.h"

#define SDA_PIN     GPIO_Pin_9      // I2C data pin
#define SCL_PIN     GPIO_Pin_8      // I2C clock pin
#define I2C_PORT    GPIOB           // I2C GPIO port
#define I2C_SCL_H   GPIO_SetBits(I2C_PORT, SCL_PIN)         // Set I2C clock high
#define I2C_SCL_L   GPIO_ResetBits(I2C_PORT, SCL_PIN)       // Set I2C clock low
#define I2C_SDA_H   GPIO_SetBits(I2C_PORT, SDA_PIN)         // Set I2C data high
#define I2C_SDA_L   GPIO_ResetBits(I2C_PORT, SDA_PIN)       // Set I2C data low
#define I2C_SDA_READ    GPIO_ReadInputDataBit(I2C_PORT, SDA_PIN) // Read I2C data

void I2C_Init(void)
{
    GPIO_InitTypeDef GPIO_InitStructure;

    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);

    GPIO_InitStructure.GPIO_Pin = SDA_PIN | SCL_PIN;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;
    GPIO_InitStructure.GPIO_OType = GPIO_OType_OD;
    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
    GPIO_Init(I2C_PORT, &GPIO_InitStructure);

    I2C_SDA_H;
    I2C_SCL_H;
}

void I2C_Start(void)
{
    I2C_SDA_H;
    I2C_SCL_H;
    I2C_SDA_L;
    I2C_SCL_L;
}

void I2C_Stop(void)
{
    I2C_SCL_L;
    I2C_SDA_L;
    I2C_SCL_H;
    I2C_SDA_H;
}

void I2C_WriteBit(uint8_t bit)
{
    if (bit)
    {
        I2C_SDA_H;
    }
    else
    {
        I2C_SDA_L;
    }

    I2C_SCL_H;
    I2C_SCL_L;
}

uint8_t I2C_ReadBit(void)
{
    uint8_t bit;

    I2C_SDA_H;
    I2C_SCL_H;
    bit = I2C_SDA_READ;
    I2C_SCL_L;

    return bit;
}

uint8_t I2C_WriteByte(uint8_t byte)
{
    uint8_t i, ack;

    for (i = 0; i < 8; i++)
    {
        I2C_WriteBit(byte & 0x80);
        byte <<= 1;
    }

    ack = I2C_ReadBit();
    return ack;
}

uint8_t I2C_ReadByte(uint8_t ack)
{
    uint8_t i, byte = 0;

    for (i = 0; i < 8; i++)
    {
        byte <<= 1;
        byte |= I2C_ReadBit();
    }

    I2C_WriteBit(ack);
    return byte;
}

void I2C_WriteAddr(uint8_t addr, uint8_t rw)
{
    I2C_WriteByte((addr << 1) | rw);
}

void LTC2990_Init(void)
{
    I2C_Start();
    I2C_WriteAddr(0x4C, 0);
    I2C_WriteByte(0x81);    // Set control register to enable temperature sensor and set conversion rate to 7 samples per second
    I2C_Stop();
}

float LTC2990_ReadTemp(void)
{
    uint8_t msb, lsb;
    int16_t temp;

    I2C_Start();
    I2C_WriteAddr(0x4C, 0);
    I2C_WriteByte(0x02);    // Set pointer to temperature register
    I2C_Start();
    I2C_WriteAddr(0x4C, 1);
    msb = I2C_ReadByte(1);
    lsb = I2C_ReadByte(0);
    I2C_Stop();

    temp = ((uint16_t)msb << 8) | lsb;

    return ((float)temp / 256.0) - 273.15;   // Convert temperature to degrees Celsius
}

int main(void)
{
    float temp;

    I2C_Init();
    LTC2990_Init();

    while (1)
    {
        temp = LTC2990_ReadTemp();
        // Do something with temperature value
    }
}

以上代码中，通过定义SDA_PIN和SCL_PIN来指定使用哪些GPIO引脚作为I2C数据和时钟线，然后通过I2C_Init函数初始化这些GPIO引脚。接下来，通过I2C_Start和I2C_Stop函数实现I2C总线的起始和停止信号。通过I2C_WriteBit和I2C_ReadBit函数实现写入和读取单个比特位，通过I2C_WriteByte和I2C_ReadByte函数实现写入和读取一个字节。最后，通过I2C_WriteAddr函数将设备地址和读写标志写入I2C总线，然后通过LTC2990_ReadTemp函数读取LTC2990的温度值。