I2C 是 philips 公司开发的一种简单的串行总线协议,用来连接微控制器与外围设备。I2C需要使用两根线:CLK时钟线和SDA数据线,I2C允许在这两根线上连接多个主机和从机。

I2C原型

/* I2C总线 */
struct i2c_bus
{
    struct i2c_device *owner;
    uint8_t lock;

    void *data;

    const struct i2c_bus_ops *ops;
};

• owner:总线拥有设备。
• lock：总线锁。
• data:总线数据。
• ops:操作方法。

/* I2C设备 */
struct i2c_device
{
    uint8_t addr;

struct i2c_bus *bus;
};

• addr:设备地址。

I2C总线方法原型（需要适配的接口）

struct i2c_bus_ops
{
    void (*clk_ctrl)(i2c_bus_t i2c_bus, uint8_t state);
    void (*sda_ctrl)(i2c_bus_t i2c_bus, uint8_t state);
    uint8_t (*read)(i2c_bus_t i2c_bus);
};

• clk_ctrl：控制时钟线。
• sda_ctrl：控制数据线。
• read：读取数据线。

初始化I2C总线

void i2c_bus_init(i2c_bus_t bus, const struct i2c_bus_ops *ops, void *data);

初始化I2C设备

void i2c_device_init(i2c_device_t device, uint8_t addr, i2c_bus_t bus);

向I2C设备寄存器写入数据

void i2c_device_write_reg(i2c_device_t device, uint8_t reg, uint8_t data);

从I2C设备寄存器读取数据

void i2c_device_write_reg(i2c_device_t device, uint8_t reg, uint8_t data);

向I2C设备传输数据（先写入再读取）

void i2c_device_transfer(i2c_device_t device,
                         const uint8_t *write_buffer,
                         size_t write_size,
                         uint8_t *read_buffer,
                         size_t read_size);

使用示例：

/* 定义I2C总线和设备 */
struct i2c_bus i2c_bus;
struct i2c_device i2c_device1;
struct i2c_device i2c_device2;

/* 适配I2C总线接口 */
void clk_ctrl(i2c_bus_t i2c_bus, uint8_t state)
{
    GPIO_WriteBit(GPIOA, GPIO_Pin_0, state);
}
void sda_ctrl(i2c_bus_t i2c_bus, uint8_t state)
{
    GPIO_WriteBit(GPIOA, GPIO_Pin_1, state);
}

uint8_t read(i2c_bus_t i2c_bus)
{
    return GPIO_ReadInputDataBit(GPIOA,GPIO_Pin_1);
}

/* 定义I2C总线方法 */
struct i2c_bus_ops i2c_ops =
{
    clk_ctrl,
    sda_ctrl,
    read
};

int main(void)
{
    /* 初始化I2C总线 */
    i2c_bus_init(&i2c_bus, &i2c_ops, NULL);
    
    /* 初始化I2C设备 */
    i2c_device_init(&i2c_device1, 0x34, &i2c_bus);
    i2c_device_init(&i2c_device2, 0x57, &i2c_bus);

    /* I2C设备写入数据 */
    i2c_device_write_reg(&i2c_device1, 0x12, 0xAA);
    i2c_device_write_reg(&i2c_device2, 0x12, 0xAA);
    
    /* I2C设备读取数据 */
    uint8_t data1 = i2c_device_read_reg(&i2c_device1, 0x12);
    uint8_t data2 = i2c_device_read_reg(&i2c_device2, 0x12);
    
    uint8 write_buffer[2] = {0x10, 0x11};
    uint8 read_buffer[2] = {0, 0};

    /* 向I2C设备传输数据 */
    i2c_device_transfer(&i2c_device1, write_buffer, sizeof(write_buffer), read_buffer, sizeof(read_buffer));
    i2c_device_transfer(&i2c_device2, write_buffer, sizeof(write_buffer), read_buffer, sizeof(read_buffer));
}

下载代码（路径：mr-library/ package / soft_i2c）

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