It's easy to use the MAX31856 sensor with Python and CircuitPython, and the Adafruit CircuitPython MAX31856 module. This module allows you to easily write Python code that reads the temperature from the thermocouple.
You can use this sensor with any CircuitPython microcontroller board or with a computer that has GPIO and Python thanks to Adafruit_Blinka, our CircuitPython-for-Python compatibility library.
CircuitPython Microcontroller Wiring
First, wire up a MAX31856 to your board exactly as shown on the previous pages for Arduino. Here's an example of wiring a Feather M0 to the sensor:
- Board 3V to sensor VIN
- Board GND to sensor GND
- Board SCK to sensor SCK
- Board MISO to sensor SDO
- Board MOSI to sensor SDI
- Board D5 to sensor CS (or any other free digital I/O pin)
Once wired to the microcontroller, make sure you connect a thermocouple to the terminal on the breakout board.
Python Computer Wiring
Since there's dozens of Linux computers/boards you can use, this shows wiring for Raspberry Pi. For other platforms, please visit the guide for CircuitPython on Linux to see whether your platform is supported.
Here's the Raspberry Pi wired with SPI:
- Pi 3V to sensor VIN
- Pi GND to sensor GND
- Pi SCK to sensor SCK
- Pi MISO to sensor SDO
- Pi MOSI to sensor SDI
- Pi D5 to sensor CS (or any other free digital I/O pin)
Once wired to the Raspberry Pi, make sure you connect a thermocouple to the terminal on the breakout board.
CircuitPython Installation of MAX31856 Library
Next, you'll need to install the Adafruit CircuitPython MAX31856 library on your CircuitPython board
First, make sure you are running the latest version of Adafruit CircuitPython for your board.
Next you'll need to install the necessary libraries to use the hardware. Carefully follow the steps to find and install these libraries from Adafruit's CircuitPython library bundle. For example the Circuit Playground Express guide has a great page on how to install the library bundle for both Express and non-Express boards.
Remember for non-Express boards like the Trinket M0, Gemma M0, and Feather/Metro M0 basic you'll need to manually install the necessary libraries from the bundle:
- adafruit_max31856.mpy
- adafruit_bus_device
Before continuing, make sure your board's lib folder has the adafruit_max31856.mpy, and adafruit_bus_device files and folders copied over.
Next connect to the board's serial REPL so you are at the CircuitPython >>> prompt.
Python Installation of MAX31856 Library
You'll need to install the Adafruit_Blinka library that provides the CircuitPython support in Python. This may also require enabling I2C on your platform and verifying you are running Python 3. Since each platform is a little different, and Linux changes often, please visit the CircuitPython on Linux guide to get your computer ready!
Once that's done, from your command line run the following command:
sudo pip3 install adafruit-circuitpython-max31856
If your default Python is version 3 you may need to run 'pip' instead. Just make sure you aren't trying to use CircuitPython on Python 2.x, it isn't supported!
CircuitPython & Python Usage
To demonstrate the usage of the sensor, initialize it and read the temperature. Remember to attach a thermocouple to the terminal on the breakout!
First initialize the SPI connection and library by running:
import board import digitalio import adafruit_max31856 spi = board.SPI() cs = digitalio.DigitalInOut(board.D5) cs.direction = digitalio.Direction.OUTPUT thermocouple = adafruit_max31856.MAX31856(spi,cs)
Now you can read the temperature property to retrieve the temperature from the sensor in degrees Celsius:
print(thermocouple.temperature)
That's all there is to reading temperature with the MAX31856 and CircuitPython code!
# SPDX-FileCopyrightText: 2021 ladyada for Adafruit Industries # SPDX-License-Identifier: MIT import board import digitalio import adafruit_max31856 # Create sensor object, communicating over the board's default SPI bus spi = board.SPI() # 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)
