Sensor experiment - 485 air temperature and humidity

Uh huh ~

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Materials and wiring

MR Development board

Single chip microcomputer TTL turn RS485 modular

Wiring instructions

Development board	TTL turn RS485 modular
A3	TXD
A2	RXD
5v	VCC
GND	GND

485 Temperature and humidity sensor module

Industrial grade chips are used , High precision import SHT20 Temperature and humidity sensor . use RS485 Hardware interface , The protocol layer is compatible with standard industry Modbus-Rtu agreement .

Wiring instructions

TTL turn RS485 modular	485 Temperature and humidity sensor	Development board
A+	TXD_A Yellow line
B-	RXD_B The white line
5v		5V Red thread
GND	GND Black line

PS： basic 485 The wiring is the same

The sample program

Get the temperature

main.py

# main.py -- put your code here!
from pyb import UART,delay
u2 = UART(2, baudrate=9600)
barray = bytearray([0x01,0x04,0x00,0x01,0x00,0x01,0x60,0x0a])  # Query frame 

while True:
    u2.write(barray)
    delay(1000) 
    if(u2.any()):
        u2by=u2.read()        #  What is returned is the content of the allowed frame 
        aa=u2by
        wendux = int.from_bytes(aa[3:5],'big')  #  temperature 
        wendu=wendux/10
        print(wendu," degree ")

Pay attention to this 485 Housing with sensor , It has an effect on the measured temperature , You can lose 2~3 degree , Is the actual temperature . Or open the shell .

Get humidity

# main.py -- put your code here!
from pyb import UART,delay
u2 = UART(2, baudrate=9600)
barray = bytearray([0x01,0x04,0x00,0x02,0x00,0x01,0x90,0x0a])  # Query frame 

while True:
    u2.write(barray)
    delay(1000) 
    if(u2.any()):
        u2by=u2.read()        #  What is returned is the content of the allowed frame 
        aa=u2by
        shidux = int.from_bytes(aa[3:5],'big')  #  humidity 
        shidu=shidux/10
        print(shidu,"%")