You can also use an Arduino Uno instead of a console cable. We spliced alligator clips with breadboard wires and connected D0 on GEMMA to pin 0 (aka RX) on the Arduino Uno board, D1 on GEMMA to Arduino pin 1 (aka TX), GEMMA GND to Arduino GND, and clip your sensor between GEMMA A1/D2 and GND.
Load a blank sketch onto your Arduino Uno:
Load the code from the previous page onto your GEMMA. Power GEMMA over USB or with a battery, open up the serial montitor and watch your sensor values pour in!