Now that we have everything hooked up and the code ready to go, let's test it out.

  • Save the CircuitPython file as "" on your computer.
  • Plug the Circuit Playground Express into your computer. 
  • Drag the "" file onto your CIRCUITPY drive that should show up in your operating system file explorer/finder program.

Test it Out!

  • Open up "" from the Circuit Playground Express on Mu
  • Click the "Serial" button on the top tool bar in Mu 1.0.0 or greater
  • Hit CTRL + D on your keyboard to re-load the code and start receiving sensor values.
  • You should start to see the sensor values being printed in the REPL.
  • Do these values make sense? Are the lower or higher than what you want?
  • It was a hot day for me so the temperature being at 29.7 C made sense.
  • Try wrapping your hand in the temperature sensor and watch the values increase.
  • Try touching the nails and see what happens to the moisture values.


Use the cup of dirt from before with some water in it to calibrate your moisture sensors (aka nails). Put enough water in the soil so that the soil is at a consistency of a damp sponge. Try changing the "dry" and "wet" moisture values at the beginning of the program so that the NeoPixels turn green when the nails are in the ideal moisture environment you have created.

DRY_VALUE = 3100  # calibrate this by hand!
WET_VALUE = 4000  # calibrate this by hand!
tempThreshhold = 43 #celius temperature of threshold for ideal compost temperature

Once the sensors are calibrated, the wiring and code are good to go. It's time to start the build!

This guide was first published on Aug 29, 2018. It was last updated on Jun 15, 2024.

This page (Testing and Calibration) was last updated on Mar 08, 2024.

Text editor powered by tinymce.