# The MIT License (MIT)
#
# Copyright (c) 2017 Radomir Dopieralski 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_max31855``
===========================
This is a CircuitPython driver for the Maxim Integrated MAX31855 thermocouple
amplifier module.
* Author(s): Radomir Dopieralski
Implementation Notes
--------------------
**Hardware:**
* Adafruit `MAX31855 Thermocouple Amplifier Breakout
<https://www.adafruit.com/product/269>`_ (Product ID: 269)
**Software and Dependencies:**
* Adafruit CircuitPython firmware for the ESP8622 and M0-based boards:
https://github.com/adafruit/circuitpython/releases
* Adafruit's Bus Device library: https://github.com/adafruit/Adafruit_CircuitPython_BusDevice
"""
try:
import struct
except ImportError:
import ustruct as struct
from adafruit_bus_device.spi_device import SPIDevice
__version__ = "0.0.0-auto.0"
__repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_MAX31855.git"
[docs]class MAX31855:
"""
Driver for the MAX31855 thermocouple amplifier.
"""
def __init__(self, spi, cs):
self.spi_device = SPIDevice(spi, cs)
self.data = bytearray(4)
def _read(self, internal=False):
with self.spi_device as spi:
spi.readinto(self.data) #pylint: disable=no-member
if self.data[3] & 0x01:
raise RuntimeError("thermocouple not connected")
if self.data[3] & 0x02:
raise RuntimeError("short circuit to ground")
if self.data[3] & 0x04:
raise RuntimeError("short circuit to power")
if self.data[1] & 0x01:
raise RuntimeError("faulty reading")
temp, refer = struct.unpack('>hh', self.data)
refer >>= 4
temp >>= 2
if internal:
return refer
return temp
@property
def temperature(self):
"""Thermocouple temperature in degrees Celsius."""
return self._read() / 4
@property
def reference_temperature(self):
"""Internal reference temperature in degrees Celsius."""
return self._read(True) * 0.625