RT-Thread-Renesa Version Board开发RT-Thread 之I2C驱动应用（SHT20）RT-Thread问答社区

Renesa Version Board开发RT-Thread 之I2C驱动应用（SHT20）

发布于 2024-07-28 13:07:41 浏览：180 订阅该版

[tocm]

# 概述
本文主要介绍如何使用Renesa Version Board上的I2C接口在RT -Thread框架下功能的应用。笔者基于SHT-Sensor详细介绍了配置的方法。还介绍了RT -Thread框架下I2C驱动的接口函数。

# 1 硬件接口介绍
## 1.1  Version Board上的I2C硬件接口
Renesa Version Board板卡扩展口提供一个标准的I2C接口，其命名如下：

![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20240728/e9f61bf093056c1f2820a3aa6ce09def.png.webp)
在如下网址能看见该IO所对应的Pin引脚：

```json
https://www.rt-thread.org/document/site/#/rt-thread-version/rt-thread-standard/hw-board/ra8d1-vision-board/ra8d1-vision-board
```

![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20240728/20bfe797ff2bc21d8273aa7e710dba79.png.webp)
## 1.2 SHT20
### 1.2.1 SHT20简介
SHT20是由Sensirion公司推出的一款数字温湿度传感器。它采用先进的CMOSens®技术，具有高精度、低功耗和长期稳定性的特点。

SHT20的测量范围涵盖了-40℃至125℃的温度和0%至100%的湿度，精确度分别为±0.3℃和±3%RH。它使用了数字式输出接口，可以通过I2C总线进行数据通信，并支持温度和湿度的实时测量。

SHT20的封装形式小巧，尺寸为3x3x1.1mm，适合各种应用场景。它具有低功耗特性，工作电压范围为2.1V至3.6V，供电电流在典型条件下为1.2mA。此外，SHT20还具有快速响应时间和强大的抗干扰能力。

### 1.2.2 SHT-20模块电路
1）SHT20硬件接口图

![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20240728/a988632b64134039f61657303346fa6f.png)

2) sensor模块电路

![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20240728/553b41989c97eba55e059b07a6225f90.png)
SHT-20实物图：

![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20240728/dfc11c8e91705116862c43f034a9f77d.png.webp)

# 2  软件实现
## 2.1 软件版本信息

![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20240728/774df2742336f20656b64a5aa8e386b4.png)

## 2.2 RT-Thread Studio创建项目
打开RT-Thread Studio,File->RT-Thread Project，打开之后看见如下页面，输入项目名称，创建项目。

![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20240728/b1159084b0429f0cac194d86c767f17e.png)

## 2.3  FSP配置I2C接口
1）选择SCI3接口，配置为I2C模式，该接口对应的IO口为P408和P409

![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20240728/49ca88b8c48f7454cebe5800c8d973c9.png.webp)

2）在Stacks面板上配置驱动的相关信息

![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20240728/726bc359c304d1d40db64865a7b57f05.png.webp)

完成以上两个步骤之后，就可以重新生成项目代码。

3） RT-Thread Studio打开驱动接口，配置完成后，使用Ctrl+S保存文件。

![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20240728/c3715eee45ed0150458dca7bbc1bed50.png.webp)

## 2.4 使能Sensor驱动
打开RT-Thread Setting，搜索sht2，找到该驱动后使能该驱动。

![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20240728/56ebafbf326a7504845377cd801b683d.png.webp)

在项目目录中，packages中已经加载该驱动程序。

![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20240728/5b8df529e7789c5233c8d116377f3062.png)

# 3 RT-Thread驱动架构
## 3.1 接口函数
一般来说，MCU的I2C设备作为主从设备进行通信。在RT-Thread中，I2C主机被虚拟化为I2C总线设备。I2C从站通过I2C设备接口与I2C总线通信。相关接口如下:

![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20240728/cd4f0645fc03eef4203d9f1ae88a93b5.png)
### 3.1.1 查找设备函数
在使用I2C总线设备之前，需要根据I2C总线设备名称获取设备句柄，以便对I2C总线设备进行操作。设备功能如下:

```c
rt_device_t rt_device_find(const char* name);
```

![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20240728/fc3f591764e7f37d7cf1c6383474a2e0.png)

**举个例子：**

注册到系统的I2C设备名称为i2co2、i2c1等。使用示例如下:

```c
#define AHT10_I2C_BUS_NAME      "i2c1"  /* Sensor connected I2C bus device name */
struct rt_i2c_bus_device *i2c_bus;      /* I2C bus device handle */

/* Find the I2C bus device and get the I2C bus device handle */
i2c_bus = (struct rt_i2c_bus_device *)rt_device_find(name);
```
### 3.1.2 数据传输函数
可以通过获取I2C总线设备句柄来使用' rt_i2c_transfer() '进行数据传输。函数原型如下:

```c
rt_size_t rt_i2c_transfer(struct rt_i2c_bus_device *bus,
                          struct rt_i2c_msg         msgs[],
                          rt_uint32_t               num);
```

![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20240728/46d3f339d09cb94a14d96db904531db0.png)

** 一个应用实例：**

Message结构体定义
 
```c
struct rt_i2c_msg
{
    rt_uint16_t addr;    /* Slave address */
    rt_uint16_t flags;   /* Reading, writing signs, etc. */
    rt_uint16_t len;     /* Read and write data bytes */
    rt_uint8_t  *buf;    /* Read and write data buffer pointer　*/
}
```
 读数据函数实现
 
```c
/* Read sensor register data */
static rt_err_t read_regs(struct rt_i2c_bus_device *bus, rt_uint8_t len, rt_uint8_t *buf)
{
    struct rt_i2c_msg msgs;

msgs.addr = AHT10_ADDR;     /* Slave address */
    msgs.flags = RT_I2C_RD;     /* Read flag */
    msgs.buf = buf;             /* Read and write data buffer pointer　*/
    msgs.len = len;             /* Read and write data bytes */

/* Call the I2C device interface to transfer data */
    if (rt_i2c_transfer(bus, &msgs, 1) == 1)
    {
        return RT_EOK;
    }
    else
    {
        return -RT_ERROR;
    }
}
```
## 3.3 驱动Demo
RT-Thread提供了一个Demo,其详细代码如下：

```c
/*
 * Program listing: This is an I2C device usage routine
 * The routine exports the i2c_aht10_sample command to the control terminal
 * Command call format: i2c_aht10_sample i2c1
 * Command explanation: The second parameter of the command is the name of the I2C bus device to be used. If it is empty, the default I2C bus device is used.
 * Program function: read the temperature and humidity data of the aht10 sensor and print.
*/

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

#define AHT10_I2C_BUS_NAME          "i2c1"  /* Sensor connected I2C bus device name */
#define AHT10_ADDR                  0x38    /* Slave address */
#define AHT10_CALIBRATION_CMD       0xE1    /* Calibration command */
#define AHT10_NORMAL_CMD            0xA8    /* General command */
#define AHT10_GET_DATA              0xAC    /* Get data command */

static struct rt_i2c_bus_device *i2c_bus = RT_NULL;     /* I2C bus device handle */
static rt_bool_t initialized = RT_FALSE;                /* Sensor initialization status */

/* Write sensor register */
static rt_err_t write_reg(struct rt_i2c_bus_device *bus, rt_uint8_t reg, rt_uint8_t *data)
{
    rt_uint8_t buf[3];
    struct rt_i2c_msg msgs;

buf[0] = reg; //cmd
    buf[1] = data[0];
    buf[2] = data[1];

msgs.addr = AHT10_ADDR;
    msgs.flags = RT_I2C_WR;
    msgs.buf = buf;
    msgs.len = 3;

/* Call the I2C device interface to transfer data */
    if (rt_i2c_transfer(bus, &msgs, 1) == 1)
    {
        return RT_EOK;
    }
    else
    {
        return -RT_ERROR;
    }
}

/* Read sensor register data */
static rt_err_t read_regs(struct rt_i2c_bus_device *bus, rt_uint8_t len, rt_uint8_t *buf)
{
    struct rt_i2c_msg msgs;

msgs.addr = AHT10_ADDR;
    msgs.flags = RT_I2C_RD;
    msgs.buf = buf;
    msgs.len = len;

/* Call the I2C device interface to transfer data */
    if (rt_i2c_transfer(bus, &msgs, 1) == 1)
    {
        return RT_EOK;
    }
    else
    {
        return -RT_ERROR;
    }
}

static void read_temp_humi(float *cur_temp, float *cur_humi)
{
    rt_uint8_t temp[6];

write_reg(i2c_bus, AHT10_GET_DATA, 0);      /* send command */
    rt_thread_mdelay(400);
    read_regs(i2c_bus, 6, temp);                /* obtian sensor data */

/* Humidity data conversion */
    *cur_humi = (temp[1] << 12 | temp[2] << 4 | (temp[3] & 0xf0) >> 4) * 100.0 / (1 << 20);
    /* Temperature data conversion */
    *cur_temp = ((temp[3] & 0xf) << 16 | temp[4] << 8 | temp[5]) * 200.0 / (1 << 20) - 50;
}

static void aht10_init(const char *name)
{
    rt_uint8_t temp[2] = {0, 0};

/* Find the I2C bus device and get the I2C bus device handle */
    i2c_bus = (struct rt_i2c_bus_device *)rt_device_find(name);

if (i2c_bus == RT_NULL)
    {
        rt_kprintf("can't find %s device!\n", name);
    }
    else
    {
        write_reg(i2c_bus, AHT10_NORMAL_CMD, temp);
        rt_thread_mdelay(400);

temp[0] = 0x08;
        temp[1] = 0x00;
        write_reg(i2c_bus, AHT10_CALIBRATION_CMD, temp);
        rt_thread_mdelay(400);
        initialized = RT_TRUE;
    }
}

static void i2c_aht10_sample(int argc, char *argv[])
{
    float humidity, temperature;
    char name[RT_NAME_MAX];

humidity = 0.0;
    temperature = 0.0;

if (argc == 2)
    {
        rt_strncpy(name, argv[1], RT_NAME_MAX);
    }
    else
    {
        rt_strncpy(name, AHT10_I2C_BUS_NAME, RT_NAME_MAX);
    }

if (!initialized)
    {
        /* Sensor initialization */
        aht10_init(name);
    }
    if (initialized)
    {
        /* Read temperature and humidity data */
        read_temp_humi(&temperature, &humidity);

rt_kprintf("read aht10 sensor humidity   : %d.%d %%\n", (int)humidity, (int)(humidity * 10) % 10);
        rt_kprintf("read aht10 sensor temperature: %d.%d \n", (int)temperature, (int)(temperature * 10) % 10);
    }
    else
    {
        rt_kprintf("initialize sensor failed!\n");
    }
}
/* Export to the msh command list */
MSH_CMD_EXPORT(i2c_aht10_sample, i2c aht10 sample);
```
# 4 系统测试
## 4.1 硬件环境
将SHT20的电源和通信接口与Version Board连接起来，其连接图如下：

![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20240728/1b9a62044e45b3e52ae1a076ba20aa05.png)
硬件实物图如下：

![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20240728/6723b275d5f582b0475617b0e19993d9.png.webp)

## 4.2 软件测试方法介绍
 RT-Thread已经提供了SHT20相关的测试命令，其具体测试方法如下：

### 4.2.1 探测传感器
sht2x 软件包提供了丰富的测试命令，项目只要在 RT-Thread 上开启 Finsh/MSH 功能即可。在做一些基于 sht2x 的应用开发、调试时，这些命令会非常实用，它可以准确的读取指传感器测量的温度与湿度。具体功能可以输入 sht20 ，可以查看完整的命令列表：

![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20240728/b56c3ba43f4fe9eb76be419030b1edc9.png)
具体方法如下：

```shell
msh />sht20 probe i2c1      #探测成功，没有错误日志
msh />
msh />sht20 probe i2c88     #探测失败，提示对应的 I2C 设备找不到
[E/sht20] can't find sht20 device on 'i2c88'
msh />
```

### 4.2.2 读取数据
探测成功之后，输入 sht20 read 即可获取温度与湿度，包括提示信息，日志如下：

```shell
msh />sht20 read
read sht20 sensor humidity   : 54.7 %
read sht20 sensor temperature: 27.3 
msh />
```
## 4.3 板卡级测试
### 4.3.1 准备测试环境
1）使用Ctrl+B组合键，编译项目代码，如下编译成功，可以看见如下log：

![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20240728/78b21330857ebbc2a37c20e1b50c913d.png)
2）下载代码到板卡中

![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20240728/b2f5167af4bb08d489c82378ab04b577.png.webp)
3）打开串口终端工具，如果代码能正常工作，可以看见如下log：

![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20240728/2679fd8e703fa753cca9b14ac042997d.png)

###  4.3.2 测试
1）查询I2C驱动接口信息，使用如下命令：

```shell
list device
```

![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20240728/1b083693aa7f44330a004a052e8f93fc.png)

2）检测SHT20在线状态

探测失败状态：

```shell
sht20 probe sci3
```

![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20240728/202ec3a8ab999aaea47e0facd654e4bc.png.webp)

探测成功状态：
 
```shell
sht20 probe sci3i
```

![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20240728/3ff72ca2111b685c1e2bf37977d4c96b.png)

改变环境温度，观察传感器温湿度的变化情况：

![screenshot_image.png](https://oss-club.rt-thread.org/uploads/20240728/636ea8e48bfb6fcc095c79ecbcff24da.png.webp)

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