RT4.0.1版本I2C挂接E2PROM注意事项

发布于 2019-09-12 12:11:56 浏览：1135 订阅该版

MCU是STM32F103, I2C挂接AT24C128, RT系统调试I2C时序时的注意事项:
RT系统版本:

\ | /
- RT -     Thread Operating System
 / | \     4.0.1 build Sep 11 2019
 2006 - 2019 Copyright by rt-thread team

1. 地址问题, RT系统I2C驱动地址是左移了一位的, (i2c_bit_send_address函数) 如下:
        /* 7-bit addr */
        addr1 = msg->addr << 1;
        if (flags & RT_I2C_RD)
            addr1 |= 1;
        ret = i2c_send_address(bus, addr1, retries);

但是E2PROM地址不需要左移, 所以初始化时地址要右移一位:

#define EP24C128_SIZE (16*1024)
	static struct ep24c128_config ep24cfg = {EP24C128_SIZE,           //24c128 16KByte
											 0x50, 	         //24c128 addr 0xA0, 需要右移一位
											 0};
	stm32f1_i2c_init("i2cE2");
	ep24c128_register("ep24c128", "i2cE2", &ep24cfg);
	gParamDev_t = rt_device_find("ep24c128");
        rt_device_open(gParamDev_t, RT_DEVICE_OFLAG_RDWR);

2. SDA引脚问题, SDA引脚初始化为推挽输出, 在获取IO电平时要切换为输入
static void setSDAMode(uint32_t mode)
{
	static GPIO_InitTypeDef GPIO_InitStruct = {SDA_Pin, 
									      GPIO_MODE_OUTPUT_PP,
									      GPIO_NOPULL,
									      GPIO_SPEED_FREQ_MEDIUM};
	GPIO_InitStruct.Mode = mode;
	HAL_GPIO_Init(SDA_Port, &GPIO_InitStruct);
}

static void stm32f1_set_sda(void *data, rt_int32_t state)
{
	setSDAMode(GPIO_MODE_OUTPUT_PP);
	HAL_GPIO_WritePin(SDA_Port, SDA_Pin, (GPIO_PinState)state);
}

static rt_int32_t  stm32f1_get_sda(void *data)
{
	setSDAMode(GPIO_MODE_INPUT);
	return (rt_int32_t)GetIo(SDA_Port, SDA_Pin);
}
这样做效率不是很高, RT在i2c-bit-ops.c中没有进行切换, 需要自行处理

3. 调试时打开RT_I2C_BIT_DEBUG选项可以方便查找问题
send start condition
ACK
ACK
ACK
write 2 bytes
ACK
recieve bytes: 0xff, NACK
read 1 byte
send stop condition