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