kiln-controller-max31856/lib/max31855spi.py

37 wiersze
1.1 KiB
Python

#!/usr/bin/python
import logging
from Adafruit_MAX31855 import MAX31855
class MAX31855SPI(object):
'''Python driver for [MAX38155 Cold-Junction Compensated Thermocouple-to-Digital Converter](http://www.maximintegrated.com/datasheet/index.mvp/id/7273)
Requires:
- adafruit's MAX31855 SPI-only device library
'''
def __init__(self, spi_dev):
self.max31855 = MAX31855.MAX31855(spi=spi_dev)
self.log = logging.getLogger(__name__)
def get(self):
'''Reads SPI bus and returns current value of thermocouple.'''
state = self.max31855.readState()
self.log.debug("status %s" % state)
if state['openCircuit']:
raise MAX31855Error('Not Connected')
elif state['shortGND']:
raise MAX31855Error('Short to Ground')
elif state['shortVCC']:
raise MAX31855Error('Short to VCC')
elif state['fault']:
raise MAX31855Error('Unknown Error')
return self.max31855.readLinearizedTempC()
class MAX31855SPIError(Exception):
def __init__(self, value):
self.value = value
def __str__(self):
return repr(self.value)