GD32F303 软件模拟I2C

以下是 GD32F303 软件模拟 I2C 的示例代码：

#include "gd32f30x.h"
#include "i2c_sw.h"

#define I2C_SCL_PIN GPIO_PIN_10
#define I2C_SDA_PIN GPIO_PIN_11
#define I2C_GPIO_PORT GPIOB

#define I2C_SCL_HIGH()  GPIO_SetBits(I2C_GPIO_PORT, I2C_SCL_PIN)
#define I2C_SCL_LOW()   GPIO_ResetBits(I2C_GPIO_PORT, I2C_SCL_PIN)
#define I2C_SDA_HIGH()  GPIO_SetBits(I2C_GPIO_PORT, I2C_SDA_PIN)
#define I2C_SDA_LOW()   GPIO_ResetBits(I2C_GPIO_PORT, I2C_SDA_PIN)
#define I2C_SDA_READ()  GPIO_ReadInputDataBit(I2C_GPIO_PORT, I2C_SDA_PIN)

void i2c_sw_delay(void)
{
    volatile uint32_t i;
    for(i=0; i<100; i++);
}

void i2c_sw_init(void)
{
    GPIO_InitPara GPIO_InitStructure;

    RCC_AHBPeriphClock_Enable(RCC_AHBPERIPH_GPIOB);

    GPIO_InitStructure.GPIO_Pin = I2C_SCL_PIN | I2C_SDA_PIN;
    GPIO_InitStructure.GPIO_Mode = GPIO_MODE_OUT;
    GPIO_InitStructure.GPIO_Speed = GPIO_SPEED_50MHZ;
    GPIO_InitStructure.GPIO_OType = GPIO_OTYPE_PP;
    GPIO_InitStructure.GPIO_PuPd = GPIO_PUPD_PULLUP;
    GPIO_Init(I2C_GPIO_PORT, &GPIO_InitStructure);

    I2C_SCL_HIGH();
    I2C_SDA_HIGH();
}

void i2c_sw_start(void)
{
    I2C_SDA_HIGH();
    I2C_SCL_HIGH();
    i2c_sw_delay();
    I2C_SDA_LOW();
    i2c_sw_delay();
    I2C_SCL_LOW();
}

void i2c_sw_stop(void)
{
    I2C_SDA_LOW();
    I2C_SCL_HIGH();
    i2c_sw_delay();
    I2C_SDA_HIGH();
    i2c_sw_delay();
}

void i2c_sw_write_byte(uint8_t data)
{
    uint8_t i;
    for(i=0; i<8; i++)
    {
        if(data & 0x80)
            I2C_SDA_HIGH();
        else
            I2C_SDA_LOW();

        i2c_sw_delay();
        I2C_SCL_HIGH();
        i2c_sw_delay();
        I2C_SCL_LOW();
        i2c_sw_delay();
        data <<= 1;
    }

    I2C_SDA_HIGH();
    i2c_sw_delay();
    I2C_SCL_HIGH();
    i2c_sw_delay();
    I2C_SCL_LOW();
}

uint8_t i2c_sw_read_byte(void)
{
    uint8_t i, data = 0;
    I2C_SDA_HIGH();
    for(i=0; i<8; i++)
    {
        data <<= 1;
        I2C_SCL_HIGH();
        i2c_sw_delay();
        if(I2C_SDA_READ() != RESET)
            data |= 0x01;
        I2C_SCL_LOW();
        i2c_sw_delay();
    }

    return data;
}

void i2c_sw_write(uint8_t addr, uint8_t reg, uint8_t data)
{
    i2c_sw_start();
    i2c_sw_write_byte(addr << 1);
    i2c_sw_write_byte(reg);
    i2c_sw_write_byte(data);
    i2c_sw_stop();
}

uint8_t i2c_sw_read(uint8_t addr, uint8_t reg)
{
    uint8_t data;
    i2c_sw_start();
    i2c_sw_write_byte(addr << 1);
    i2c_sw_write_byte(reg);
    i2c_sw_start();
    i2c_sw_write_byte((addr << 1) | 0x01);
    data = i2c_sw_read_byte();
    i2c_sw_stop();
    return data;
}

使用方法：

1. 在主函数中调用 `i2c_sw_init()` 进行初始化。
2. 调用 `i2c_sw_write()` 写入数据，或调用 `i2c_sw_read()` 读取数据。
3. 注意在每次读写之前先调用 `i2c_sw_start()`，读写完成后调用 `i2c_sw_stop()`。