Product Introduction:

       The product adopts industrial grade chip, high-precision imported SHT20 temperature and humidity sensor to ensure the excellent reliability, high precision and interchangeability of the product. Using RS485 hardware interface (with lightning protection design), the protocol layer is compatible with standard industrial Modbus-Rtu protocol. This product integrates the MODBUS protocol and the common protocol. The user can choose the communication protocol. The common protocol has an automatic upload function (connecting RS485 through the serial port adjustment tool will automatically output temperature and humidity).

0x03:Read keep register

0x04: Read input register

0x06:Write a single keep register

0x10:Write more keep registers

Modbus Frame format:

Master send format:

The responseformat of slave:

MODBUSCOMMAND

Master read temperature command frame(0x04):

The response data from slave:

Temperature value=0x131,converted to a decimal 305,the actual temperature value = 305 / 10 = 30.5°

Note: the temperature is signed hexadecimal number, temperature value = 0xFF33, converted to a decimal - 205, the actual temperature = -20.5 °;

Master read humidity command frame(0x04)

The response data from slave:

Humidity value = 0x222, converted to a decimal 546, actual humidity value = 546/10 = 54.6 %;

Continuous read temperature and humidity command frame(0x04):

The response data from slave:

Read keep register(0x03):

Readdevice address from the slave:

The response data from slave:

Modify the contents of the registers(0x06):

Modify the slave address register:

Modify the slave address:0x08 = 8

The response data from slave(And send the same):

Continuously change keep registers(0x10):

Slave address :0x20 = 32

Baud rate :0x2580 = 9600

The response data from slave:

General Protocal

The default baud rates9600 (the user can set), 8 bits of data, one stop, no check

RS485

CMD	instructions
READ	Report triggered a temperature and humidity (27.4°,67.7% 温度27.4°湿度67.7%)
AUTO	Start the temperature and humidity automatically report function(Same as above)
STOP	Stop the temperature and humidity automatically report function
BR:XXXX	Set the baud rate 9600~19200 (BR:9600)
TC:XX.X	Set the temperature calibration(-10.0~10.0) (TC:02.0温度修正值为2.0°)
HC:XX.X	Set the humidityration(-10.0~10.0) (HC:-05.1 湿度修正值为 -5.1%)
HZ:XXX	Set the temperature and humidity reporting rate(0.5,1,2,5,10) (HZ:2 reporting rate 2Hz)
PARAM	Read the system current Settings

PARAM CMD:

TC:0.0,HC:0.0,BR:9600,HZ:1  ->Temp calibration 0.0, Humi calibration0.0, Baud rate 9600,report rate 1Hz

SLAVE_ADD:1                      ->MODBU Slave address 1