68 lines
2.0 KiB
Python
68 lines
2.0 KiB
Python
# DS18x20 temperature sensor driver for MicroPython.
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# MIT license; Copyright (c) 2016 Damien P. George
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import onewire
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from machine import Pin
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from micropython import const
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_CONVERT = const(0x44)
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_RD_SCRATCH = const(0xBE)
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_WR_SCRATCH = const(0x4E)
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class DS18X20:
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__species = {}
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__first_init = True
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def __new__(cls, pin, *args, **kwargs):
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if pin not in cls.__species.keys():
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cls.__first_init = True
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cls.__species[pin] = object.__new__(cls)
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return cls.__species[pin]
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def __init__(self, pin):
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if self.__first_init:
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self.__first_init = False
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self._ow = onewire.OneWire(Pin(pin, pull=Pin.PULL_UP))
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self._buf = bytearray(9)
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self._roms = self.scan()
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if len(self._roms) == 0:
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raise AttributeError("Cannot find a DS18X20")
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def scan(self):
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return [rom for rom in self._ow.scan() if rom[0] in (0x10, 0x22, 0x28)]
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def convert_temp(self):
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self._ow.reset(True)
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self._ow.writebyte(self._ow.SKIP_ROM)
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self._ow.writebyte(_CONVERT)
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def read_scratch(self, rom):
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self._ow.reset(True)
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self._ow.select_rom(rom)
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self._ow.writebyte(_RD_SCRATCH)
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self._ow.readinto(self._buf)
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if self._ow.crc8(self._buf):
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raise Exception("CRC error")
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return self._buf
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def read_temp(self, rom):
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buf = self.read_scratch(rom)
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if rom[0] == 0x10:
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if buf[1]:
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t = buf[0] >> 1 | 0x80
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t = -((~t + 1) & 0xFF)
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else:
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t = buf[0] >> 1
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return t - 0.25 + (buf[7] - buf[6]) / buf[7]
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else:
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t = buf[1] << 8 | buf[0]
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if t & 0x8000: # sign bit set
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t = -((t ^ 0xFFFF) + 1)
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return t / 16
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def temperature(self):
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temp = []
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self.convert_temp()
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for rom in self._roms:
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temp.append(round(self.read_temp(rom), 2))
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return temp [0] if len(temp) == 1 else tuple(temp)
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