RT-Thread 设备驱动I2C浅析及使用
由于 I2C 可以控制多从机的属性，设备驱动模型分为 I2C总线设备（类似与Linux里面的I2C适配器） + I2C从设备；
系统I2C设备驱动主要实现 I2C 总线设备驱动，而具体的I2C 从设备的实现则调用I2C总线设备ops
访问 I2C 总线设备
一般情况下 MCU 的 I2C 器件都是作为主机和从机通讯，在 RT-Thread 中将 I2C 主机虚拟为 I2C总线设备，I2C 从机通过 I2C 设备接口和 I2C 总线通讯，相关接口如下所示：
| 函数 | 描述 |
|---|---|
| rt_device_find() | 根据 I2C 总线设备名称查找设备获取设备句柄 |
| rt_i2c_transfer() | 传输数据 |
使用方式参考官方文档即可，在此不做赘述。
驱动源码分析
i2c_core.c i2c总线协议控制的核心实现
i2c_dev.c i2c总线设备框架输线
i2c-bit-ops.c I/O模拟I2C的驱动实现
drv_soft_i2c.c I/O模拟I2C的底层硬件支持
先分析 I2C 总线设备注册的流程
在 drv_soft_i2c.c 中
INIT_BOARD_EXPORT(rt_hw_i2c_init);
则 OS 运行时会自启动 rt_hw_i2c_init 进行 模拟I2C 相关硬件IO的初始化
rt_hw_i2c_init -> rt_i2c_bit_add_bus -> rt_i2c_bus_device_register -> rt_i2c_bus_device_device_init -> rt_device_register
初始的配置
#ifdef BSP_USING_I2C1
#define I2C1_BUS_CONFIG \
{ \
.scl = BSP_I2C1_SCL_PIN, \
.sda = BSP_I2C1_SDA_PIN, \
.bus_name = "i2c1", \
}
#endif
这样使用时就可以通过 "i2c1" 来控制从设备了
I2C传输功能源码分析
rt_i2c_transfer -> i2c_bit_xfer
static rt_size_t i2c_bit_xfer(struct rt_i2c_bus_device *bus,
struct rt_i2c_msg msgs[],
rt_uint32_t num)
{
struct rt_i2c_msg *msg;
struct rt_i2c_bit_ops *ops = bus->priv;
rt_int32_t i, ret;
rt_uint16_t ignore_nack; bit_dbg("send start condition\n");
i2c_start(ops);
for (i = ; i < num; i++)
{
msg = &msgs[i];
ignore_nack = msg->flags & RT_I2C_IGNORE_NACK;
if (!(msg->flags & RT_I2C_NO_START)) // 没有RT_I2C_NO_START
{
if (i) // 主要用于读操作
{
i2c_restart(ops);
}
ret = i2c_bit_send_address(bus, msg); //发送器件地址
if ((ret != RT_EOK) && !ignore_nack)
{
bit_dbg("receive NACK from device addr 0x%02x msg %d\n",
msgs[i].addr, i);
goto out;
}
}
if (msg->flags & RT_I2C_RD) //读取数据
{
ret = i2c_recv_bytes(bus, msg);
if (ret >= )
bit_dbg("read %d byte%s\n", ret, ret == ? "" : "s");
if (ret < msg->len)
{
if (ret >= )
ret = -RT_EIO;
goto out;
}
}
else //发送数据
{
ret = i2c_send_bytes(bus, msg);
if (ret >= )
bit_dbg("write %d byte%s\n", ret, ret == ? "" : "s");
if (ret < msg->len)
{
if (ret >= )
ret = -RT_ERROR;
goto out;
}
}
}
ret = i; out:
bit_dbg("send stop condition\n");
i2c_stop(ops); return ret;
}
我们以 24c02 的 读写 来分析 i2C驱动
static rt_size_t at24cxx_write(rt_device_t dev, rt_off_t pos, const void *buffer, rt_size_t size)
{
struct at24cxx_device *at24cxx;
const struct at24cxx_config *cfg;
struct rt_i2c_msg msg[];
rt_uint8_t mem_addr[] = {,};
rt_size_t ret = ;
RT_ASSERT(dev != ); at24cxx = (struct at24cxx_device *) dev; RT_ASSERT(at24cxx->parent.user_data != );
cfg = (const struct at24cxx_config *) at24cxx->parent.user_data; if(pos > cfg->size)
{
return ;
} if(pos + size > cfg->size)
{
size = cfg->size - pos;
} // 写入寻址地址
msg[].addr = cfg->addr;
msg[].flags = cfg->flags | RT_I2C_WR;
if(cfg->size < ) // at24c01 at24c02, 一页8字节，寻址地址8位
{
mem_addr[] = (rt_uint8_t) pos;
msg[].buf = (rt_uint8_t *) mem_addr;
msg[].len = ;
}
else // at24c04/08/16 一页16字节，寻址地址9/10/11位
{
mem_addr[] = (pos >> );
mem_addr[] = (rt_uint8_t) pos;
msg[].buf = (rt_uint8_t *) mem_addr;
msg[].len = ;
} // 使用RT_I2C_NO_START，直接写入buffer数据
msg[].addr = cfg->addr;
msg[].flags = cfg->flags | RT_I2C_WR | RT_I2C_NO_START;
msg[].buf = (rt_uint8_t *) buffer;
msg[].len = size; ret = rt_i2c_transfer(at24cxx->bus, msg, );
return (ret == ) ? size : ;
}
static rt_size_t at24cxx_read(rt_device_t dev, rt_off_t pos, void *buffer, rt_size_t size)
{
struct at24cxx_device *at24cxx;
const struct at24cxx_config *cfg;
struct rt_i2c_msg msg[];
rt_uint8_t mem_addr[] = {,};
rt_size_t ret = ;
RT_ASSERT(dev != ); at24cxx = (struct at24cxx_device *) dev; RT_ASSERT(at24cxx->parent.user_data != );
cfg = (const struct at24cxx_config *) at24cxx->parent.user_data; if(pos >= cfg->size) //寻址地址超标
{
return ;
} if(pos + size > cfg->size) // size超标
{
size = cfg->size - pos;
} msg[].addr = cfg->addr;
msg[].flags = cfg->flags | RT_I2C_WR;
if(cfg->size < ) // at24c01 at24c02, 一页8字节，寻址地址8位
{
mem_addr[] = (rt_uint8_t) pos;
msg[].buf = (rt_uint8_t *) mem_addr;
msg[].len = ;
}
else // at24c04/08/16 一页16字节，寻址地址9/10/11位
{
mem_addr[] = (pos >> );
mem_addr[] = (rt_uint8_t) pos;
msg[].buf = (rt_uint8_t *) mem_addr;
msg[].len = ;
} msg[].addr = cfg->addr;
msg[].flags = cfg->flags | RT_I2C_RD;
msg[].buf = (rt_uint8_t *) buffer;
msg[].len = size; ret = rt_i2c_transfer(at24cxx->bus, msg, );
return (ret == ) ? size : ; }
可以看到 i2c 读写 EEPROM 通过发送多个 msg 来实现 写寻址地址在进行读写操作，同时通过 RT_I2C_NO_START 使用读写场景
i2C设备应用实例
24c02设备实例代码
#include <rtthread.h>
#include <rtdevice.h>
#include "at24cxx.h" /** at24cxx设备结构体 */
struct at24cxx_device
{
struct rt_device parent;
struct rt_i2c_bus_device *bus;
}; /* RT-Thread device interface */
static rt_err_t at24cxx_init(rt_device_t dev)
{
return RT_EOK;
} static rt_err_t at24cxx_open(rt_device_t dev, rt_uint16_t oflag)
{
return RT_EOK;
} static rt_err_t at24cxx_close(rt_device_t dev)
{
return RT_EOK;
} static rt_err_t at24cxx_control(rt_device_t dev, int cmd, void *args)
{
return RT_EOK;
} /**
* @brief at24cxx设备读操作
* @param[in] dev 设备句柄
* @param[in] pos i2c写寻址地址
* @param[in] *buffer 读出数据的指针
* @param[in] size 读出数据的长度
* @return 返回读出成功的字节数
* - 0 读出失败
* - Others 读出成功的字节数
*/
static rt_size_t at24cxx_read(rt_device_t dev, rt_off_t pos, void *buffer, rt_size_t size)
{
struct at24cxx_device *at24cxx;
const struct at24cxx_config *cfg;
struct rt_i2c_msg msg[];
rt_uint8_t mem_addr[] = {,};
rt_size_t ret = ;
RT_ASSERT(dev != ); at24cxx = (struct at24cxx_device *) dev; RT_ASSERT(at24cxx->parent.user_data != );
cfg = (const struct at24cxx_config *) at24cxx->parent.user_data; if(pos >= cfg->size) //寻址地址超标
{
return ;
} if(pos + size > cfg->size) // size超标
{
size = cfg->size - pos;
} msg[].addr = cfg->addr;
msg[].flags = cfg->flags | RT_I2C_WR;
if(cfg->size < ) // at24c01 at24c02, 一页8字节，寻址地址8位
{
mem_addr[] = (rt_uint8_t) pos;
msg[].buf = (rt_uint8_t *) mem_addr;
msg[].len = ;
}
else // at24c04/08/16 一页16字节，寻址地址9/10/11位
{
mem_addr[] = (pos >> );
mem_addr[] = (rt_uint8_t) pos;
msg[].buf = (rt_uint8_t *) mem_addr;
msg[].len = ;
} msg[].addr = cfg->addr;
msg[].flags = cfg->flags | RT_I2C_RD;
msg[].buf = (rt_uint8_t *) buffer;
msg[].len = size; ret = rt_i2c_transfer(at24cxx->bus, msg, );
return (ret == ) ? size : ; } /**
* @brief at24cxx设备写操作
* @param[in] dev 设备句柄
* @param[in] pos i2c写寻址地址
* @param[in] *buffer 写入数据的指针
* @param[in] size 写入数据的长度
* @return 返回写入成功的字节数
* - 0 写入失败
* - Others 写入成功的字节数
*/
#if 0 // 连续页写测试
static rt_size_t at24cxx_write(rt_device_t dev, rt_off_t pos, const void *buffer, rt_size_t size)
{
struct at24cxx_device *at24cxx;
const struct at24cxx_config *cfg;
struct rt_i2c_msg msg[];
rt_uint8_t mem_addr[] = {,};
rt_size_t ret = ;
RT_ASSERT(dev != ); at24cxx = (struct at24cxx_device *) dev; RT_ASSERT(at24cxx->parent.user_data != );
cfg = (const struct at24cxx_config *) at24cxx->parent.user_data; if(pos > cfg->size)
{
return ;
} if(pos + size > cfg->size)
{
size = cfg->size - pos;
} /*计算出要写的页数和分页*/
rt_uint8_t NumOfPage = ; // 总页写数，包括写的不完整页
rt_uint8_t Addr = ; // 页写的寻址地址
rt_uint8_t count = ; // 页写入的字节数
rt_uint8_t i; if(size > (PAGE_SIZE - pos%PAGE_SIZE))
{
count = PAGE_SIZE - pos%PAGE_SIZE; // 写入的第一页长度
NumOfPage = (size - count)/PAGE_SIZE; // 剩余写入的完整页数
if((size - (count + NumOfPage*PAGE_SIZE)) > )
NumOfPage = NumOfPage + ;
else
NumOfPage = NumOfPage + ;
}
else
{
NumOfPage = ;
} for(i=; i<NumOfPage; i++)
{
if(i == )
{
Addr = pos;
if(NumOfPage == )
{
count = size;
}
else
{
count = PAGE_SIZE - pos%PAGE_SIZE;
}
}
else if((i == NumOfPage-) && (NumOfPage > ))
{
Addr = pos - pos%PAGE_SIZE + i*PAGE_SIZE;
count = pos + size - Addr;
}
else
{
Addr = pos - pos%PAGE_SIZE + i*PAGE_SIZE;
count = PAGE_SIZE;
} // 写入寻址地址
msg[].addr = cfg->addr;
msg[].flags = cfg->flags | RT_I2C_WR;
if(cfg->size < ) // at24c01 at24c02, 一页8字节，寻址地址8位
{
mem_addr[] = (rt_uint8_t) Addr;
msg[].buf = (rt_uint8_t *) mem_addr;
msg[].len = ;
}
else // at24c04/08/16 一页16字节，寻址地址9/10/11位
{
mem_addr[] = (Addr >> );
mem_addr[] = (rt_uint8_t) Addr;
msg[].buf = (rt_uint8_t *) mem_addr;
msg[].len = ;
} // 使用RT_I2C_NO_START，直接写入buffer数据
msg[].addr = cfg->addr;
msg[].flags = cfg->flags | RT_I2C_WR | RT_I2C_NO_START;
msg[].buf = (rt_uint8_t *) buffer+count;
msg[].len = count; ret = rt_i2c_transfer(at24cxx->bus, msg, );
if(ret != )
return ;
}
return count;
}
#endif #if 1 // 不支持连续页写
static rt_size_t at24cxx_write(rt_device_t dev, rt_off_t pos, const void *buffer, rt_size_t size)
{
struct at24cxx_device *at24cxx;
const struct at24cxx_config *cfg;
struct rt_i2c_msg msg[];
rt_uint8_t mem_addr[] = {,};
rt_size_t ret = ;
RT_ASSERT(dev != ); at24cxx = (struct at24cxx_device *) dev; RT_ASSERT(at24cxx->parent.user_data != );
cfg = (const struct at24cxx_config *) at24cxx->parent.user_data; if(pos > cfg->size)
{
return ;
} if(pos + size > cfg->size)
{
size = cfg->size - pos;
} // 写入寻址地址
msg[].addr = cfg->addr;
msg[].flags = cfg->flags | RT_I2C_WR;
if(cfg->size < ) // at24c01 at24c02, 一页8字节，寻址地址8位
{
mem_addr[] = (rt_uint8_t) pos;
msg[].buf = (rt_uint8_t *) mem_addr;
msg[].len = ;
}
else // at24c04/08/16 一页16字节，寻址地址9/10/11位
{
mem_addr[] = (pos >> );
mem_addr[] = (rt_uint8_t) pos;
msg[].buf = (rt_uint8_t *) mem_addr;
msg[].len = ;
} // 使用RT_I2C_NO_START，直接写入buffer数据
msg[].addr = cfg->addr;
msg[].flags = cfg->flags | RT_I2C_WR | RT_I2C_NO_START;
msg[].buf = (rt_uint8_t *) buffer;
msg[].len = size; ret = rt_i2c_transfer(at24cxx->bus, msg, );
return (ret == ) ? size : ;
}
#endif #ifdef RT_USING_DEVICE_OPS
/** at24cxx设备操作ops */
const static struct rt_device_ops at24cxx_ops =
{
at24cxx_init,
at24cxx_open,
at24cxx_close,
at24cxx_read,
at24cxx_write,
at24cxx_control
};
#endif /**
* @brief at24cxx设备注册
* @param[in] *fm_device_name 设备名称
* @param[in] *i2c_bus i2c总线设备名称
* @param[in] *user_data 用户数据 at24cxx_config
* @return 函数执行结果
* - RT_EOK 执行成功
* - Others 失败
*/
rt_err_t at24cxx_register(const char *fm_device_name, const char *i2c_bus, void *user_data)
{
static struct at24cxx_device at24cxx_drv;
struct rt_i2c_bus_device *bus; bus = rt_i2c_bus_device_find(i2c_bus);
if (bus == RT_NULL)
{
return RT_ENOSYS;
} at24cxx_drv.bus = bus;
at24cxx_drv.parent.type = RT_Device_Class_Block;
#ifdef RT_USING_DEVICE_OPS
at24cxx_drv.parent.ops = &at24cxx_ops;
#else
at24cxx_drv.parent.init = at24cxx_init;
at24cxx_drv.parent.open = at24cxx_open;
at24cxx_drv.parent.close = at24cxx_close;
at24cxx_drv.parent.read = at24cxx_read;
at24cxx_drv.parent.write = at24cxx_write;
at24cxx_drv.parent.control = at24cxx_control;
#endif at24cxx_drv.parent.user_data = user_data; return rt_device_register(&at24cxx_drv.parent, fm_device_name, RT_DEVICE_FLAG_RDWR);
}
/** at24cxx设备用户操作配置结构体 */
struct at24cxx_config
{
rt_uint32_t size; //设备的总容量
rt_uint16_t addr; //设备地址
rt_uint16_t flags; //I2C操作标志
}; /**
* @brief at24cxx设备注册
* @param[in] *fm_device_name 设备名称
* @param[in] *i2c_bus i2c总线设备名称
* @param[in] *user_data 用户数据 at24cxx_config
* @return 函数执行结果
* - RT_EOK 执行成功
* - Others 失败
*/
extern rt_err_t at24cxx_register(const char *e2m_device_name, const char *i2c_bus, void *user_data);
24c02设备驱动使用示例
static struct at24cxx_config at24c02_config =
{
.size = , // 容量，单位字节
.addr = 0x50, // 注意该地址为没有移位之前的地址不是0xA0
.flags = ,
}; static void at24c02_sample(int argc, char *argv[])
{
rt_err_t ret;
rt_uint8_t test_data[] = {0x12, 0x34, 0x56, 0x78};
rt_uint8_t tmp_data[]; // memset(test_data, 0x55, 100); ret = at24cxx_register("at24c02", "i2c1", &at24c02_config); rt_device_t at24c02_dev = rt_device_find("at24c02");
if (at24c02_dev == RT_NULL)
{
rt_kprintf("at24c02 sample run failed! can't find %s device!\n", "at24c02");
return;
}
rt_device_open(at24c02_dev, RT_DEVICE_FLAG_RDWR); ret = rt_device_write(at24c02_dev, , test_data, );
if(ret != )
{
rt_kprintf("at24c02 write error %d\n", ret);
}
rt_thread_mdelay();
ret = rt_device_read(at24c02_dev, , tmp_data, );
if(ret != )
{
rt_kprintf("at24c02 read error %d\n", ret);
}
else
{
rt_kprintf("at24c02 read data %02x %02x %02x %02x\n", tmp_data[], tmp_data[], tmp_data[], tmp_data[]);
}
}
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