Introduction

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A CircuitPython driver for the MAX31856 Universal Thermocouple Amplifier

Dependencies

This driver depends on:

Please ensure all dependencies are available on the CircuitPython filesystem. This is easily achieved by downloading the Adafruit library and driver bundle.

Usage Example

import board
import busio
import digitalio
import adafruit_max31856

# create a spi object
spi = busio.SPI(board.SCK, board.MOSI, board.MISO)

# allocate a CS pin and set the direction
cs = digitalio.DigitalInOut(board.D5)
cs.direction = digitalio.Direction.OUTPUT

# create a thermocouple object with the above
thermocouple = adafruit_max31856.MAX31856(spi, cs)

# print the temperature!
print(thermocouple.temperature)

Contributing

Contributions are welcome! Please read our Code of Conduct before contributing to help this project stay welcoming.

Building locally

Zip release files

To build this library locally you’ll need to install the circuitpython-build-tools package.

python3 -m venv .env
source .env/bin/activate
pip install circuitpython-build-tools

Once installed, make sure you are in the virtual environment:

source .env/bin/activate

Then run the build:

circuitpython-build-bundles --filename_prefix adafruit-circuitpython-max31856 --library_location .

Sphinx documentation

Sphinx is used to build the documentation based on rST files and comments in the code. First, install dependencies (feel free to reuse the virtual environment from above):

python3 -m venv .env
source .env/bin/activate
pip install Sphinx sphinx-rtd-theme

Now, once you have the virtual environment activated:

cd docs
sphinx-build -E -W -b html . _build/html

This will output the documentation to docs/_build/html. Open the index.html in your browser to view them. It will also (due to -W) error out on any warning like Travis will. This is a good way to locally verify it will pass.

Table of Contents

Simple test

Ensure your device works with this simple test.

examples/max31856_simpletest.py
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import board
import busio
import digitalio
import adafruit_max31856
# create a spi object
spi = busio.SPI(board.SCK, board.MOSI, board.MISO)

# allocate a CS pin and set the direction
cs = digitalio.DigitalInOut(board.D0)
cs.direction = digitalio.Direction.OUTPUT

# create a thermocouple object with the above
thermocouple = adafruit_max31856.MAX31856(spi,cs)

# print the temperature!
print(thermocouple.temperature)

MAX31856

CircuitPython module for the MAX31856 Universal Thermocouple Amplifier. See examples/simpletest.py for an example of the usage.

  • Author(s): Bryan Siepert

Implementation Notes

Hardware:

Software and Dependencies:

class adafruit_max31856.MAX31856(spi, cs, thermocouple_type=3)

Driver for the MAX31856 Universal Thermocouple Amplifier

Parameters:
  • spi_bus (SPI) – The SPI bus the MAX31856 is connected to.
  • cs (Pin) – The pin used for the CS signal.
  • thermocouple_type (ThermocoupleType) – The type of thermocouple. Default is Type K.
fault

A dictionary with the status of each fault type where the key is the fault type and the value is a bool if the fault is currently active

Key Fault type
“cj_range” Cold junction range fault
“tc_range” Thermocouple range fault
“cj_high” Cold junction high threshold fault
“cj_low” Cold junction low threshold fault
“tc_high” Thermocouple high threshold fault
“tc_low” Thermocouple low threshold fault
“voltage” Over/under voltage fault
“open_tc” Thermocouple open circuit fault
reference_temperature

The temperature of the cold junction in degrees celsius. (read-only)

reference_temperature_thresholds

The cold junction’s low and high temperature thresholds as a (low_temp, high_temp) tuple

temperature

The temperature of the sensor and return its value in degrees celsius. (read-only)

temperature_thresholds

The thermocouple’s low and high temperature thresholds as a (low_temp, high_temp) tuple

class adafruit_max31856.ThermocoupleType

An enum-like class representing the different types of thermocouples that the MAX31856 can use. The values can be referenced like ThermocoupleType.K or ThermocoupleType.S Possible values are

  • ThermocoupleType.B
  • ThermocoupleType.E
  • ThermocoupleType.J
  • ThermocoupleType.K
  • ThermocoupleType.N
  • ThermocoupleType.R
  • ThermocoupleType.S
  • ThermocoupleType.T

Indices and tables