rtt标准版的软件i2c使用

软件i2c配置

在rtt配备的env环境中，通过menuconfig进入项目配置界面，依次选择Hardware Drivers Config -> On-chip Peripheral Drivers -> Enable I2C1 BUS (software simulation)

在使能软件i2c后，会进入i2c的scl和sda的io配置，在rtt中stm32的多类gpio（如PA、PB）被降维编码为一维id，如

  • PC0: $2*16 + 0 = 32$
  • PF1: $5*16 + 1 = 81$

通过UI界面配置的结果，如SCL和SDA对应的io pin口，可以在rtconfig.h中看到对应的宏定义接口。

i2c设备的封装

rtt中的i2c设备是对rt_device类型设备的再封装，对应i2c总线设备的类（结构体）的父类即为rt_device。

i2c总线设备结构体如下所示

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/*for i2c bus driver*/
struct rt_i2c_bus_device
{
    struct rt_device parent;
    const struct rt_i2c_bus_device_ops *ops;
    rt_uint16_t  flags;
    struct rt_mutex lock;
    rt_uint32_t  timeout;
    rt_uint32_t  retries;
    void *priv;
};

device封装格式与linux类似，ops指的是针对当前字符设备操作的一组函数指针，如open、close、read以及write等。

i2c总线设备的使用

  1. 声明i2c设备
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#define I2C_BUS_NAME          "i2c1"                    /* 传感器连接的I2C总线设备名称 */
static struct rt_i2c_bus_device *i2c_bus = RT_NULL;     /* I2C总线设备句柄 */
  1. 通过rt_device类的find方法连接总线设备句柄
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i2c_bus = (struct rt_i2c_bus_device *)rt_device_find(I2C_BUS_NAME);
if (i2c_bus == RT_NULL) {
    rt_kprintf("can't find %s device!\n", I2C_BUS_NAME);
    return -RT_ERROR;
}
  1. rt_device类的open方法尝试开启设备，并检查函数返回（引用设备，每次open使设备ref++）
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if (rt_device_open(&i2c_bus->parent, RT_NULL) != RT_EOK) {
    rt_kprintf("open %s device failed!\n", I2C_BUS_NAME);
    return -RT_ERROR;
}
  1. 读写数据-transfer方法
  • RT_I2C_WR：写标志
  • RT_I2C_RD：读标志
  • RT_I2C_ADDR_10BIT：10bit地址模式
  • RT_I2C_NO_START：无起始位，与无结束位实现拼接
  • RT_I2C_NO_STOP：同上
  • RT_I2C_IGNORE_NACK：发送时无视来自接收方的NACK
  • RT_I2C_NO_READ_ACK：读取时不产生ACK
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/*?
 * I2C bus transfer
 *
 * @param bus the I2C bus device
 * @param msgs the I2C message array
 * @param num the number of I2C message
 *
 * @return the number of messages sent
 */
rt_size_t rt_i2c_transfer(struct rt_i2c_bus_device *bus,
                          struct rt_i2c_msg         msgs[],
                          rt_uint32_t               num);

struct rt_i2c_msg msgs; /* i2c消息结构体 */
msgs.addr = addr;       /* i2c从机地址 */
msgs.buf = buf;         /* 数据缓冲区 */
msgs.len = len;         /* 数据长度 */
msgs.flags = RT_I2C_WR; /* 写标志 */

if (rt_i2c_transfer(i2c_bus, &msgs, 1) != 1){
    return -RT_ERROR;
}
  1. 读写数据-master封装方法
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/*?
 * I2C master send data
 *
 * @param[in] *bus the I2C bus device
 * @param[in] addr the I2C slave address
 * @param[in] flags the I2C message flags
 * @param[in] *buf the data buffer
 * @param[in] count the data buffer length
 *
 * @return the number of bytes sent
 */
rt_size_t rt_i2c_master_send(struct rt_i2c_bus_device *bus,
                             rt_uint16_t               addr,
                             rt_uint16_t               flags,
                             const rt_uint8_t         *buf,
                             rt_uint32_t               count);
/*?
 * I2C master receive data
 *
 * @param[in] *bus the I2C bus device
 * @param[in] addr the I2C slave address
 * @param[in] flags the I2C message flags
 * @param[out] *buf the data buffer
 * @param[out] count the received data length
 *
 * @return the number of bytes receive
 */
rt_size_t rt_i2c_master_recv(struct rt_i2c_bus_device *bus,
                             rt_uint16_t               addr,
                             rt_uint16_t               flags,
                             rt_uint8_t               *buf,
                             rt_uint32_t               count);
  1. 关闭设备（取消引用，ref–）
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if (rt_device_close(&i2c_bus->parent) != RT_EOK) {
    rt_kprintf("close %s device failed!\n", I2C_BUS_NAME);
    return -RT_ERROR;
}