It's easy to use the MAX31855 sensor with Python and CircuitPython, and the Adafruit CircuitPython MAX31855 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 MAX31855 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 Vdd
- Board GND to sensor GND
- Board SCK to sensor CLK
- Board MISO to sensor DO
- Board D5 to sensor CS (or any other free digital I/O pin)
Python Computer Wiring
Since there's dozens of Linux computers/boards you can use we will show 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 3.3V to sensor Vin
- Pi GND to sensor GND
- Pi SCLK to sensor CLK
- Pi MISO to sensor DO
- Pi GPIO 5 to sensor CS
CircuitPython Installation of MAX31855 Library
Next you'll need to install the Adafruit CircuitPython MAX31855 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. You can do this in two ways:
1. Easy: In the example at the bottom of the page, click the blue "Download Project Bundle" button to get the example code and libraries for the version of CircuitPython you're using.
2. Manual method: 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_max31855.mpy
- adafruit_bus_device
Before continuing make sure your board's lib folder or root filesystem has the adafruit_max31855.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 MAX31855 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 (even though this uses SPI not I2C) 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-max31855
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 we'll initialize it and read the temperature. First initialize the SPI connection and library by running:
import board import digitalio import adafruit_max31855 spi = board.SPI() cs = digitalio.DigitalInOut(board.D5) max31855 = adafruit_max31855.MAX31855(spi, cs)
Now you can read the temperature property to retrieve the temperature from the sensor in degrees Celsius:
print('Temperature: {} degrees C'.format(max31855.temperature))
That's all there is to reading temperature with the MAX31855 and CircuitPython code!
# SPDX-FileCopyrightText: 2021 ladyada for Adafruit Industries
# SPDX-License-Identifier: MIT
import time
import board
import digitalio
import adafruit_max31855
spi = board.SPI()
cs = digitalio.DigitalInOut(board.D5)
max31855 = adafruit_max31855.MAX31855(spi, cs)
while True:
tempC = max31855.temperature
tempF = tempC * 9 / 5 + 32
print("Temperature: {} C {} F ".format(tempC, tempF))
time.sleep(2.0)
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