SHT2x package

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1. Introduction

The SHT2x software package provides the basic function of using the temperature and humidity sensor sht20, as well as the optional function of the software average filter. This article introduces the basic functions of the software package and the Finsh/MSH test commands.

The basic functions are mainly determined by the sensor aht10: within the range of input voltage 1.8v-3.3v, the measuring range and accuracy of temperature and humidity are shown in the table below

Function	Range	Accuracy
Temperature	-40℃-125℃	±0.3℃
Humidity	0%-100%	±3%

1.1 Directory structure

Name	Description
sht20.h	Sensor header file
sht20.c	Sensor use source code
SConscript	RT-Thread default build script
README.md	Package Instructions
SHT20_datasheet.pdf	Official Data Sheet

1.2 License

The SHT2x software package complies with the Apache-2.0 license, see the LICENSE file for details.

1.3 Dependency

Rely on RT-Thread I2C device driver framework.

2 Get the package

To use the sht2x package, you need to select it in the package manager of RT-Thread. The specific path is as follows:

RT-Thread online packages
    peripheral libraries and drivers --->
        [*] sht2x: digital humidity and temperature sensor sht2x driver library --->
        [*] Enable average filter by software
        (10) The number of averaging
        (1000) Peroid of sampling data(unit ms)
               Version (latest) --->

The configuration instructions for each function are as follows:

• sht2x: digital humidity and temperature sensor sht2x driver library: choose to use the sht20 software package;
• Enable average filter by software: enable the average filter function of the software for collecting temperature and humidity;
• The number of averaging: the number of samples to average;
• Peroid of sampling data(unit ms): The period of sampling data, the time unit is ms;
• Version: Configure the software package version, the latest version is the default.

Then let RT-Thread's package manager automatically update, or use the pkgs --update command to update the package to the BSP.

3 Use sht2x package

According to the previous introduction, after obtaining the sht2x software package, you can use the sensor sht20 and Finsh/MSH commands to test according to the API provided below. The details are as follows.

3.1 API

3.1.1 Initialization

sht20_device_t sht20_init(const char *i2c_bus_name)

According to the bus name, the corresponding SHT20 device is automatically initialized. The specific parameters and return description are as follows

Parameters	Description
name	i2c device name
Back	Description
!= NULL	will return sht20 device object
= NULL	Find failed

3.1.2 Deinitialization

void sht20_deinit(sht20_device_t dev)

If the device is no longer used, deinitialization will reclaim the relevant resources of the sht20 device. The specific parameters are described in the following table

Parameters	Description
dev	sht20 device object

3.1.3 Read temperature

float sht20_read_temperature(sht20_device_t dev)

Read the temperature measurement value through the sht20 sensor, and return the floating-point temperature value. The specific parameters and return description are as follows

Parameters	Description
dev	sht20 device object
Back	Description
!= 0.0	Measuring temperature value
=0.0	Measurement failed

3.1.4 Read humidity

float sht20_read_humidity(sht20_device_t dev)

Read the humidity measurement value through the sht20 sensor and return the floating-point humidity value. The specific parameters and return description are as follows

Parameters	Description
dev	sht20 device object
Back	Description
!= 0.0	Measuring humidity value
=0.0	Measurement failed

3.1.5 Setting parameters

rt_err_t sht20_set_param(sht20_device_t dev, sht20_param_type_t type, rt_uint8_t value)

Use the sht20 parameter command to set the value of related parameters. The specific parameters and return description are as follows

Parameters	Description
dev	sht20 device object
type	sht20 command type
value	Set command value
Back	Description
RT_EOK	Set successfully
-RT_ERROR	Setting failed

There are three types of sht20 commands, as follows:

SHT20_PARAM_PRECISION         //Set ADC conversion digits
SHT20_PARAM_BATTERY_STATUS    //Set the battery reminder status
SHT20_PARAM_HEATING           //Set whether to heat

There are four types of ADC conversion bits, which are represented as follows

SHT20_RES_12_14BIT 0x00  // Humidity 12 bits, temperature 14 bits (default)
SHT20_RES_8_12BIT 0x01   // 8 bits for humidity, 12 bits for temperature
SHT20_RES_10_13BIT 0x80  // 10 bits for humidity, 12 bits for temperature
SHT20_RES_11_11BIT 0x81  // Humidity 11 bits, temperature 11 bits

3.1.6 Read parameters

rt_err_t sht20_get_param(sht20_device_t dev, sht20_param_type_t type, rt_uint8_t *value)

Through the sht20 parameter command, read the value of related parameters, the specific parameters and return description are as follows

Parameters	Description
dev	sht20 device object
type	sht20 command type
value	Get command value
Back	Description
RT_EOK	Successfully obtained
-RT_ERROR	Get failed

3.2 Finsh/MSH test commands

The sht2x software package provides a wealth of test commands, and the project only needs to enable the Finsh/MSH function on RT-Thread. When doing some application development and debugging based on sht2x, these commands will be very useful. It can accurately read the temperature and humidity measured by the sensor. For specific functions, you can enter sht20 to view the complete command list

msh />sht20
Usage:
sht20 probe <dev_name>-probe sensor by given name
sht20 read-read sensor sht20 data
msh />

3.2.1 Detect the sensor on the specified i2c bus

When using the sht20 command for the first time, directly enter sht20 probe <dev_name>, where <dev_name> is the designated i2c bus, for example: i2c0`. If there is this sensor, no error will be prompted; if there is no such sensor on the bus, it will display a prompt that the relevant device cannot be found, the log is as follows:

msh />sht20 probe i2c1 #Detection is successful, no error log
msh />
msh />sht20 probe i2c88 #Detection failed, prompting that the corresponding I2C device could not be found
[E/sht20] can't find sht20 device on'i2c88'
msh />

3.2.2 Read data

After the detection is successful, enter sht20 read to get the temperature and humidity, including prompt information, the log is as follows:

msh />sht20 read
read sht20 sensor humidity: 54.7%
read sht20 sensor temperature: 27.3
msh />

4 Notes

Nothing.

5 Contact

• Maintenance: Ernest
• Homepage: https://github.com/RT-Thread-packages/sht2x