# The MIT License (MIT)
#
# Copyright (c) 2017 Carter Nelson for Adafruit Industries
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
"""
`adafruit_ds18x20`
====================================================
Driver for Dallas 1-Wire temperature sensor.
* Author(s): Carter Nelson
"""
__version__ = "0.0.0-auto.0"
__repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_DS18x20.git"
import time
from micropython import const
from adafruit_onewire.device import OneWireDevice
_CONVERT = b"\x44"
_RD_SCRATCH = b"\xBE"
_WR_SCRATCH = b"\x4E"
_CONVERSION_TIMEOUT = const(1)
RESOLUTION = (9, 10, 11, 12)
# Maximum conversion delay in seconds, from DS18B20 datasheet.
_CONVERSION_DELAY = {9: 0.09375, 10: 0.1875, 11: 0.375, 12: 0.750}
[docs]class DS18X20:
"""Class which provides interface to DS18X20 temperature sensor."""
def __init__(self, bus, address):
if address.family_code == 0x10 or address.family_code == 0x28:
self._address = address
self._device = OneWireDevice(bus, address)
self._buf = bytearray(9)
self._conv_delay = _CONVERSION_DELAY[12] # pessimistic default
else:
raise ValueError("Incorrect family code in device address.")
@property
def temperature(self):
"""The temperature in degrees Celsius."""
self._convert_temp()
return self._read_temp()
@property
def resolution(self):
"""The programmable resolution. 9, 10, 11, or 12 bits."""
return RESOLUTION[self._read_scratch()[4] >> 5 & 0x03]
@resolution.setter
def resolution(self, bits):
if bits not in RESOLUTION:
raise ValueError("Incorrect resolution. Must be 9, 10, 11, or 12.")
self._buf[0] = 0 # TH register
self._buf[1] = 0 # TL register
self._buf[2] = RESOLUTION.index(bits) << 5 | 0x1F # configuration register
self._write_scratch(self._buf)
def _convert_temp(self, timeout=_CONVERSION_TIMEOUT):
with self._device as dev:
dev.write(_CONVERT)
start_time = time.monotonic()
if timeout > 0:
dev.readinto(self._buf, end=1)
# 0 = conversion in progress, 1 = conversion done
while self._buf[0] == 0x00:
if time.monotonic() - start_time > timeout:
raise RuntimeError(
"Timeout waiting for conversion to complete."
)
dev.readinto(self._buf, end=1)
return time.monotonic() - start_time
def _read_temp(self):
# pylint: disable=invalid-name
buf = self._read_scratch()
if self._address.family_code == 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]
t = buf[1] << 8 | buf[0]
if t & 0x8000: # sign bit set
t = -((t ^ 0xFFFF) + 1)
return t / 16
def _read_scratch(self):
with self._device as dev:
dev.write(_RD_SCRATCH)
dev.readinto(self._buf)
return self._buf
def _write_scratch(self, buf):
with self._device as dev:
dev.write(_WR_SCRATCH)
dev.write(buf, end=3)
[docs] def start_temperature_read(self):
"""Start asynchronous conversion, returns immediately.
Returns maximum conversion delay [seconds] based on resolution."""
with self._device as dev:
dev.write(_CONVERT)
return _CONVERSION_DELAY[self.resolution]
[docs] def read_temperature(self):
"""Read the temperature. No polling of the conversion busy bit
(assumes that the conversion has completed)."""
return self._read_temp()