10. Controlling 1-wire devices¶
The 1-wire bus is a serial bus that uses just a single wire for communication (in addition to wires for ground and power). The DS18B20 temperature sensor is a very popular 1-wire device, and here we show how to use the onewire module to read from such a device.
For the following code to work you need to have at least one DS18B20 temperature sensor with its data line connected to GPIO12. You must also power the sensors and connect a 4.7k Ohm resistor between the data pin and the power pin.
import time import machine import onewire # the device is on GPIO12 dat = machine.Pin(12) # create the onewire object ds = onewire.DS18B20(onewire.OneWire(dat)) # scan for devices on the bus roms = ds.scan() print('found devices:', roms) # loop 10 times and print all temperatures for i in range(10): print('temperatures:', end=' ') ds.convert_temp() time.sleep_ms(750) for rom in roms: print(ds.read_temp(rom), end=' ') print()
Note that you must execute the
convert_temp() function to initiate a
temperature reading, then wait at least 750ms before reading the value.