micropython_ds18x20's Introduction

micropython_ds18x20

this is a really basic tutorial for using the Dallas DS18b20 temperature sensor
on the esp8266 port of micropython

i used the lolin esp8266 D1 mini board and a cheap ds18b20 breakout shield .

the ds18b20 sensors are often sold in a waterproof sealed unit with just the wires exposed. You will need to pull up the data line (normally yellow or white) to VCC with a 4.7kOhm resistor. I am not covering this aspect in this tutorial but this is explained well elsewhere

OneWire and ds18x20 micropython library are both in the standard esp8266 port of micropython so it is really easy to get started.
The data line on this particular shield is connected to D2 on the Wemos (GPIO 4)
create a dat object to specify the Pin the one wire data is supplied through
pass the dat object into a onewire , and pass that into a ds18x20
each ds18b20 has a 64bit address fixed at manufacture which you access by the scan function, you need this address to run the read_temp function
a convert_temp function is called every time a reading is taken
then you can run read_temp function which returns temp in Celcius

dat = machine.Pin(4) 
ds = ds18x20.DS18X20(onewire.OneWire(dat))
roms = ds.scan() #this should return a single entry in a byte array
while True:
    ds.convert_temp()
    time.sleep_ms(750) #temp conversion takes 750ms from datasheet
    temp = ds.read_temp(roms[0])
    print(temp)
    time.sleep(5)

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