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"""
Onewire interface using w1 sysfs
"""
import os
import errno
import re
import sys
import time
import random
class OnewireException(Exception):
pass
class SensorNotPresent(OnewireException):
pass
class ReadFailed(OnewireException):
pass
class OutOfRange(OnewireException):
pass
_sensors = {}
with open(os.path.join(os.path.realpath(os.path.dirname(__file__)), 'onewire-sensors.txt'), 'r') as sensors_file:
for line in sensors_file:
line = line.strip()
address, name = line.split(' ', 1)
_sensors[name] = address
def sensors():
return list(_sensors.keys())
class SensorFacade(object):
def __init__(self, addr, name):
self._addr = addr
self._name = name
self._cached = None
self._cachets = None
self._backoff = None
def _path(self):
addr = self._addr.replace('.', '-').lower()
return '/sys/devices/w1_bus_master1/{0}/w1_slave'.format(addr)
def get_temperature(self):
path = self._path()
try: os.stat(path)
except OSError, ose:
if ose.errno == errno.ENOENT:
raise SensorNotPresent, path
else:
raise
with open(path, 'r') as w1_file:
w1_data = w1_file.read()
if w1_data.strip() == '':
raise ReadFailed, path
match = re.search(r'\st=(\d+)', w1_data)
temp = float(match.group(1)) / 1000
return temp
@property
def temperature(self):
if self._cachets > time.time() - 50:
return self._cached
if self._backoff > time.time():
if self._cachets > time.time() - 250:
return self._cached
return None
try:
rv = self.get_temperature()
if rv > 65 or rv < -25:
raise OutOfRange, (self._path(), rv)
self._cached = rv
self._cachets = time.time()
self._backoff = None
print '\033[32m', self._name, 'read', self._cached, '\033[m'
return self._cached
except SensorNotPresent:
self._backoff = time.time() + 2 + random.expovariate(1./3.) * 2
print '\033[31m', self._name, 'SensorNotPresent back-off', self._backoff - time.time(), '\033[m'
if self._cachets > time.time() - 250:
return self._cached
raise
except OutOfRange:
self._backoff = time.time() + 15 + random.expovariate(1./4.) * 10
print '\033[33m', self._name, 'OutOfRange back-off', self._backoff - time.time(), '\033[m'
if self._cachets > time.time() - 250:
return self._cached
raise
def sensor(name):
if name not in _sensors:
raise OnewireException('Don\'t know about sensor %s' % name)
return SensorFacade('%s' % _sensors[name], name)
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