Hook your sensor up to pin A1/D2 and ground. In the photo above we're testing an analog velostat step sensor as seen in the Firewalker Sneakers. You can also debug a digital sensor like the on/off antics of the vibration switches or tilt ball

Load this code onto your GEMMA using a regular USB cable:

// GEMMA serial debugging

#include <SoftwareSerial.h>

#define SENSOR_PIN       1 // Analog input for sensor

// Establish software serial on digital pins 0 and 1
SoftwareSerial mySerial = SoftwareSerial(0,1); 

int sensorValue;       // Current filtered pressure reading

void setup() {

  // Set internal pullup resistor for sensor pin (analog 1 is digital 2)
  pinMode(2, INPUT_PULLUP); 


void loop() {
  sensorValue = analogRead(SENSOR_PIN);


Make sure you have the console cable driver installed, then it should show up like a regular serial port in the Arduino serial monitor.

Once you can see your sensor values, you can adjust your program to trigger events at different thresholds!

This guide was first published on Aug 20, 2014. It was last updated on Mar 08, 2024.

This page (Use it!) was last updated on Aug 19, 2014.

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