92 lines
2.4 KiB
Python
92 lines
2.4 KiB
Python
# 1-Wire 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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import _onewire as _ow
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class OneWireError(Exception):
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pass
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class OneWire:
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SEARCH_ROM = const(0xf0)
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MATCH_ROM = const(0x55)
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SKIP_ROM = const(0xcc)
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def __init__(self, pin):
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self.pin = pin
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self.pin.init(pin.OPEN_DRAIN)
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def reset(self, required=False):
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reset = _ow.reset(self.pin)
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if required and not reset:
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raise OneWireError
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return reset
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def readbit(self):
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return _ow.readbit(self.pin)
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def readbyte(self):
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return _ow.readbyte(self.pin)
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def readinto(self, buf):
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for i in range(len(buf)):
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buf[i] = _ow.readbyte(self.pin)
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def writebit(self, value):
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return _ow.writebit(self.pin, value)
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def writebyte(self, value):
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return _ow.writebyte(self.pin, value)
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def write(self, buf):
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for b in buf:
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_ow.writebyte(self.pin, b)
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def select_rom(self, rom):
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self.reset()
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self.writebyte(MATCH_ROM)
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self.write(rom)
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def scan(self):
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devices = []
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diff = 65
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rom = False
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for i in range(0xff):
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rom, diff = self._search_rom(rom, diff)
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if rom:
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devices += [rom]
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if diff == 0:
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break
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return devices
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def _search_rom(self, l_rom, diff):
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if not self.reset():
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return None, 0
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self.writebyte(SEARCH_ROM)
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if not l_rom:
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l_rom = bytearray(8)
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rom = bytearray(8)
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next_diff = 0
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i = 64
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for byte in range(8):
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r_b = 0
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for bit in range(8):
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b = self.readbit()
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if self.readbit():
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if b: # there are no devices or there is an error on the bus
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return None, 0
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else:
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if not b: # collision, two devices with different bit meaning
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if diff > i or ((l_rom[byte] & (1 << bit)) and diff != i):
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b = 1
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next_diff = i
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self.writebit(b)
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if b:
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r_b |= 1 << bit
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i -= 1
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rom[byte] = r_b
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return rom, next_diff
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def crc8(self, data):
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return _ow.crc8(data)
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