rtthread用gpio模拟iic

在RT-Thread中，可以利用GPIO模拟IIC总线。以下是一个简单的例子：

#include <rtthread.h>
#include <rtdevice.h>

#define IIC_SCL_PIN     GET_PIN(B, 10)
#define IIC_SDA_PIN     GET_PIN(B, 11)

static void iic_gpio_delay(void)
{
    rt_thread_mdelay(1);
}

static void iic_gpio_set_sda(rt_bool_t value)
{
    rt_pin_write(IIC_SDA_PIN, value);
}

static void iic_gpio_set_scl(rt_bool_t value)
{
    rt_pin_write(IIC_SCL_PIN, value);
}

static rt_bool_t iic_gpio_get_sda(void)
{
    return rt_pin_read(IIC_SDA_PIN);
}

static void iic_gpio_start(void)
{
    iic_gpio_set_sda(RT_TRUE);
    iic_gpio_set_scl(RT_TRUE);
    iic_gpio_delay();
    iic_gpio_set_sda(RT_FALSE);
    iic_gpio_delay();
    iic_gpio_set_scl(RT_FALSE);
}

static void iic_gpio_stop(void)
{
    iic_gpio_set_sda(RT_FALSE);
    iic_gpio_set_scl(RT_TRUE);
    iic_gpio_delay();
    iic_gpio_set_sda(RT_TRUE);
    iic_gpio_delay();
}

static rt_bool_t iic_gpio_write_byte(rt_uint8_t data)
{
    rt_uint8_t i;

    for (i = 0; i < 8; i++)
    {
        iic_gpio_set_sda((data & 0x80) ? RT_TRUE : RT_FALSE);
        iic_gpio_set_scl(RT_TRUE);
        iic_gpio_delay();
        iic_gpio_set_scl(RT_FALSE);
        iic_gpio_delay();
        data <<= 1;
    }

    iic_gpio_set_sda(RT_TRUE);
    iic_gpio_set_scl(RT_TRUE);
    iic_gpio_delay();

    if (iic_gpio_get_sda())
    {
        return RT_FALSE;
    }

    iic_gpio_set_scl(RT_FALSE);

    return RT_TRUE;
}

static rt_uint8_t iic_gpio_read_byte(rt_bool_t ack)
{
    rt_uint8_t i;
    rt_uint8_t data = 0;

    iic_gpio_set_sda(RT_TRUE);

    for (i = 0; i < 8; i++)
    {
        iic_gpio_set_scl(RT_TRUE);
        iic_gpio_delay();
        data <<= 1;
        data |= iic_gpio_get_sda() ? 0x01 : 0x00;
        iic_gpio_set_scl(RT_FALSE);
        iic_gpio_delay();
    }

    if (ack)
    {
        iic_gpio_set_sda(RT_FALSE);
    }

    iic_gpio_set_scl(RT_TRUE);
    iic_gpio_delay();
    iic_gpio_set_scl(RT_FALSE);
    iic_gpio_delay();

    if (ack)
    {
        iic_gpio_set_sda(RT_TRUE);
    }

    return data;
}

static rt_err_t iic_gpio_transfer(rt_uint8_t addr, rt_uint8_t *buf, rt_uint16_t len, rt_bool_t read)
{
    rt_uint8_t i;
    rt_err_t result = RT_EOK;

    iic_gpio_start();

    if (!iic_gpio_write_byte(addr))
    {
        result = -RT_EIO;
        goto __exit;
    }

    if (read)
    {
        for (i = 0; i < len - 1; i++)
        {
            buf[i] = iic_gpio_read_byte(RT_TRUE);
        }

        buf[len - 1] = iic_gpio_read_byte(RT_FALSE);
    }
    else
    {
        for (i = 0; i < len; i++)
        {
            if (!iic_gpio_write_byte(buf[i]))
            {
                result = -RT_EIO;
                goto __exit;
            }
        }
    }

__exit:

    iic_gpio_stop();

    return result;
}

rt_err_t iic_gpio_init(void)
{
    rt_pin_mode(IIC_SCL_PIN, PIN_MODE_OUTPUT_OD);
    rt_pin_mode(IIC_SDA_PIN, PIN_MODE_OUTPUT_OD);
    rt_pin_write(IIC_SCL_PIN, RT_TRUE);
    rt_pin_write(IIC_SDA_PIN, RT_TRUE);

    return RT_EOK;
}

#ifdef RT_USING_FINSH
#include <finsh.h>

static void iic_gpio_test(void)
{
    rt_uint8_t buf[8];

    rt_memset(buf, 0, sizeof(buf));

    iic_gpio_transfer(0x50, buf, sizeof(buf), RT_FALSE);

    rt_kprintf("write: ");

    for (int i = 0; i < sizeof(buf); i++)
    {
        rt_kprintf("%02X ", buf[i]);
    }

    rt_kprintf("\n");

    rt_kprintf("read: ");

    rt_memset(buf, 0, sizeof(buf));

    iic_gpio_transfer(0x50, buf, sizeof(buf), RT_TRUE);

    for (int i = 0; i < sizeof(buf); i++)
    {
        rt_kprintf("%02X ", buf[i]);
    }

    rt_kprintf("\n");
}

FINSH_FUNCTION_EXPORT(iic_gpio_test, iic gpio test)
#endif /* RT_USING_FINSH */

在这个例子中，我们使用GPIO B10和B11作为IIC总线的SCL和SDA引脚。我们定义了一个iic_gpio_transfer函数来实现IIC总线的读写操作。我们还定义了一些辅助函数来模拟IIC总线的信号，如iic_gpio_start、iic_gpio_stop、iic_gpio_write_byte和iic_gpio_read_byte函数。最后，我们在FINSH shell中定义了一个iic_gpio_test函数来测试我们的IIC模拟代码。