This project explains the basic method for using the GR-COTTON board equipped with LED lights to send a message to a smartphone.


You will need a GR-COTTON board and a USB cable (Micro B type).

Make sure the white jumper on the reverse side of GR-COTTON is moved to the “3V3 USB” side. If it is set to the BATT side, remove and reinsert it into the USB side.


Importing the Library

1. Obtain the Picalico Library

Please note that the Picalico library was dicontinued in 2016. However, information on this product can still be found on the Japanese version of the Casio Picalico website.

Go to the Picalico FREE user agreement page and download “GR-COTTON sample code/library.”


2. Import the Library

Start up the web compiler or IDE for GR and open the GR-COTTON sketch.

Import the library based on the usage environments.

For Web Compiler:

Open the context menu in the project folder and click on “upload.”


Upload the zip folder containing the downloaded library as is. This completes the import.


For IDE for GR:

Go to the menu and select Sketch → Import Library → Add Library, and select the target zip file. This completes the import process.


Sample Program for Temperature Display

This sample sends the temperature to a smartphone using the Picalico library. Copy and paste the sample into the sketch and write the sketch to GR-COTTON to make the LED blink in red, blue and green.

#include <arduino.h>
#include <PicalicoClass.h>
Picalico pica(LOW); // set LED to active high
// the setup routine runs once when you press reset:
void setup() {
    pica.attach(22, 23, 24); //set pins red, green and blue
    pica.writeTemperature(getTemperature(0)); // write temperature into picalico
// the loop routine runs over and over again forever:
void loop() {

Read a Blinking Light with Picalico Reader

Install the Picalico Reader with the smartphone app.

When Picalico Reader recognizes the blinking light on GR-COTTON, it displays the temperature.

Picalico Reader can also display characters, numbers, percentages, and time, so use this sample program to expand your options!