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circuitpython/esp8266/modules/ds18x20.py

51 lines
1.4 KiB

# DS18x20 temperature sensor driver for MicroPython.
# MIT license; Copyright (c) 2016 Damien P. George
from micropython import const
_CONVERT = const(0x44)
_RD_SCRATCH = const(0xbe)
_WR_SCRATCH = const(0x4e)
class DS18X20:
def __init__(self, onewire):
self.ow = onewire
self.buf = bytearray(9)
def scan(self):
return [rom for rom in self.ow.scan() if rom[0] == 0x10 or rom[0] == 0x28]
def convert_temp(self):
self.ow.reset(True)
self.ow.writebyte(self.ow.SKIP_ROM)
self.ow.writebyte(_CONVERT)
def read_scratch(self, rom):
self.ow.reset(True)
self.ow.select_rom(rom)
self.ow.writebyte(_RD_SCRATCH)
self.ow.readinto(self.buf)
if self.ow.crc8(self.buf):
raise Exception('CRC error')
return self.buf
def write_scratch(self, rom, buf):
self.ow.reset(True)
self.ow.select_rom(rom)
self.ow.writebyte(_WR_SCRATCH)
self.ow.write(buf)
def read_temp(self, rom):
buf = self.read_scratch(rom)
if rom[0] == 0x10:
if buf[1]:
t = buf[0] >> 1 | 0x80
t = -((~t + 1) & 0xff)
else:
t = buf[0] >> 1
return t - 0.25 + (buf[7] - buf[6]) / buf[7]
else:
t = buf[1] << 8 | buf[0]
if t & 0x8000: # sign bit set
t = -((t ^ 0xffff) + 1)
return t / 16