I2C没有应答信号，求助一下

static rt_err_t pmic_i2c_read(struct rt_i2c_bus_device *pmic_i2c_bus,
                              rt_uint8_t addr, rt_uint8_t reg, rt_uint16_t *data)
{
    struct rt_i2c_msg msg[2];
    rt_uint8_t send_buf[2];
    send_buf[0] = reg;
    msg[0].addr  = addr;
    msg[0].flags = RT_I2C_WR;
    msg[0].len   = 1;
    msg[0].buf   = send_buf;
    msg[1].addr  = addr;
    msg[1].flags = RT_I2C_RD;
    msg[1].len   = 2;
    msg[1].buf   = (rt_uint8_t *)data;
    if (rt_i2c_transfer(pmic_i2c_bus, msg, 2) == 2)
    {    
        return RT_EOK;
    }
    else
    {
        rt_kprintf("read reg 0x%x error\n", reg);
         return -RT_ERROR;
    }
}
static rt_err_t pmic_write(struct rt_i2c_bus_device *pmic_i2c_bus,
                    rt_uint8_t addr, rt_uint8_t reg, rt_uint16_t data)
{
    struct rt_i2c_msg msg;
    rt_uint8_t send_buf[2];
    send_buf[0] = reg;
    send_buf[1] = data>>8;
    send_buf[2] = data & 0xFF;
    msg.addr = addr;
    msg.flags = RT_I2C_WR;
    msg.len = 3;
    msg.buf = send_buf;
    if (rt_i2c_transfer(pmic_i2c_bus, &msg, 1) == 1)
    {            
        return RT_EOK;
    }     
    else
    {
        rt_kprintf("write reg 0x%x, data %d error\n", reg, data);
         return -RT_ERROR;
    }
}