53 lines
1.4 KiB
Python
53 lines
1.4 KiB
Python
# DS18x20 temperature sensor driver for MicroPython.
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# MIT license; Copyright (c) 2016 Damien P. George
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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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def __init__(self, onewire):
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self.ow = onewire
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self.buf = bytearray(9)
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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 write_scratch(self, rom, buf):
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self.ow.reset(True)
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self.ow.select_rom(rom)
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self.ow.writebyte(_WR_SCRATCH)
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self.ow.write(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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