The Arduino code presented below works well on Gemma v1 and v2. But if you have an M0 board you must use the CircuitPython code on the next page of this guide, no Arduino IDE required!
Make sure to to download the Mini MLX90614, NeoPixel and TinyWireM Library. Below is a sample sketch that will change the color of the NeoPixel ring depending on temperature values - copy it into your Adafruit Arduino IDE as-is and then mod the temperature values to make it your own. Remember that to program GEMMA you need to download the special Adafruit version of the Arduino IDE from the Introduction to GEMMA guide.
// SPDX-FileCopyrightText: 2018 Limor Fried for Adafruit Industries
// SPDX-License-Identifier: MIT

This is a library for the MLX90614 temperature sensor SPECIFICALLY

Requires the latest TinyWireM with repeated-start support

NOT FOR REGULAR ARDUINOS! Use the regular Adafruit_MLX90614 for that

  Designed specifically to work with the MLX90614 sensors in the
  adafruit shop

  These sensors use I2C to communicate, 2 pins are required to  
  Adafruit invests time and resources providing this open source code, 
  please support Adafruit and open-source hardware by purchasing 
  products from Adafruit!

  Written by Limor Fried/Ladyada for Adafruit in any redistribution

#include <Adafruit_MLX90614.h>
#include <Adafruit_NeoPixel.h>

// change these to adjust the range of temperatures you want to measure 
// (these are in Farenheit)
#define COLDTEMP 60
#define HOTTEMP  80

#define PIN 1
Adafruit_NeoPixel strip = Adafruit_NeoPixel(24, PIN, NEO_GRB + NEO_KHZ800);

Adafruit_MLX90614 mlx = Adafruit_MLX90614();

void setup() {
  strip.begin();; // Initialize all pixels to 'off'

void loop() {
  uint8_t red, blue;
  float temp = mlx.readObjectTempF();

  if (temp < COLDTEMP) temp = COLDTEMP;
  if (temp > HOTTEMP) temp = HOTTEMP;

  // map temperature to red/blue color
  // hotter temp -> more red
  red = map(temp, COLDTEMP, HOTTEMP, 0, 255);  
  // hotter temp -> less blue
  blue = map(temp, COLDTEMP, HOTTEMP, 255, 0);  

  colorWipe(strip.Color(red, 0, blue), 0);
  delay(50); // can adjust this for faster/slower updates

// Fill the dots one after the other with a color
void colorWipe(uint32_t c, uint8_t wait) {
  for(uint16_t i=0; i<strip.numPixels(); i++) {
      strip.setPixelColor(i, c);;

This guide was first published on Apr 10, 2014. It was last updated on May 21, 2024.

This page (Arduino Code) was last updated on May 21, 2024.

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