It's easy to use the MLX90640 sensor with Python and CircuitPython, and the Adafruit CircuitPython MLX90640 module. This module allows you to easily write Python code that reads temperature using the thermal camera.
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 MLX90640 to your board for an I2C connection, exactly as shown below. Here's an example of wiring a Feather M4 to the sensor with I2C:
- Board 3V to sensor VIN (red wire)
- Board GND to sensor GND (black wire)
- Board SCL to sensor SCL (yellow wire)
- Board SDA to sensor SDA (blue wire)
Python Computer Wiring
Since there are 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 I2C:
- Pi 3V to sensor VCC (red wire)
- Pi GND to sensor GND (black wire)
- Pi SCL to sensor SCL (yellow wire)
- Pi SDA to sensor SDA (blue wire)
CircuitPython Installation of MLX90640 Library
You'll need to install the Adafruit CircuitPython MLX90640 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. Our CircuitPython starter guide has a great page on how to install the library bundle.
You'll need to manually install the necessary libraries from the bundle:
- adafruit_mlx90640.mpy
- adafruit_bus_device
Before continuing, make sure your board's lib folder has the adafruit_mlx90640.mpy, and adafruit_bus_device files and folders copied over.
Python Installation of MLX90640 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-mlx90640
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 run the mlx90640_simpletest.py
program which prints the temperatures or shows them as ASCII. As this example is too complicated to run from the REPL, you'll save the following code to your board as code.py and connect to the serial console to see the output.
# SPDX-FileCopyrightText: 2021 ladyada for Adafruit Industries # SPDX-License-Identifier: MIT import time import board import busio import adafruit_mlx90640 PRINT_TEMPERATURES = False PRINT_ASCIIART = True i2c = busio.I2C(board.SCL, board.SDA, frequency=800000) # i2c = board.STEMMA_I2C() # For using the built-in STEMMA QT connector on a microcontroller mlx = adafruit_mlx90640.MLX90640(i2c) print("MLX addr detected on I2C") print([hex(i) for i in mlx.serial_number]) mlx.refresh_rate = adafruit_mlx90640.RefreshRate.REFRESH_2_HZ frame = [0] * 768 while True: stamp = time.monotonic() try: mlx.getFrame(frame) except ValueError: # these happen, no biggie - retry continue print("Read 2 frames in %0.2f s" % (time.monotonic() - stamp)) for h in range(24): for w in range(32): t = frame[h * 32 + w] if PRINT_TEMPERATURES: print("%0.1f, " % t, end="") if PRINT_ASCIIART: c = "&" # pylint: disable=multiple-statements if t < 20: c = " " elif t < 23: c = "." elif t < 25: c = "-" elif t < 27: c = "*" elif t < 29: c = "+" elif t < 31: c = "x" elif t < 33: c = "%" elif t < 35: c = "#" elif t < 37: c = "X" # pylint: enable=multiple-statements print(c, end="") print() print()
If you change the values for the variables at the top of the program, you can switch from printing out an ASCII image to printing out the temperatures in a grid. Change PRINT_TEMPERATURES
to True
and PRINT_ASCIIART
to False
, so that the two lines are as follows:
PRINT_TEMPERATURES = True PRINT_ASCIIART = False
Connect to the serial console to see the temperatures printed out in a grid. Fitting them all in a proper grid involved making my terminal window significantly larger than the default size.
That's all there is to using the MLX90640 with CircuitPython!
Page last edited January 22, 2025
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