class TemperatureSensor:
class _Const:
CONVERT = const(0x44)
RD_SCRATCH = const(0xbe)
def __init__(self, pin):
self._onewire = OneWire(pin)
self._buffer = bytearray(9)
self._rom = [rom for rom in self._onewire.scan() if rom[0] in (0x10, 0x22, 0x28)][0]
self._convert_temp()
def _convert_temp(self):
self._onewire.reset(True)
self._onewire.writebyte(self._onewire.SKIP_ROM)
self._onewire.writebyte(self._Const.CONVERT)
def _read_scratch(self):
self._onewire.reset(True)
self._onewire.select_rom(self._rom)
self._onewire.writebyte(TemperatureSensor._Const.RD_SCRATCH)
self._onewire.readinto(self._buffer)
if self._onewire.crc8(self._buffer):
raise Exception('Temperature sensor::CRC error')
return self._buffer
def read(self):
buffer = self._read_scratch()
if self._rom[0] == 0x10:
if self._buffer[1]:
t = self._buffer[0] >> 1 | 0x80
t = -((~t + 1) & 0xff)
else:
t = self._buffer[0] >> 1
return t - 0.25 + (self._buffer[7] - self._buffer[6]) / self._buffer[7]
else:
t = self._buffer[1] << 8 | self._buffer[0]
if t & 0x8000:
t = -((t ^ 0xffff) + 1)
return t / 16
