COTTON Sketch Reference

Let’s have a bit of fun creating unique gadgets with the GR-COTTON board and web compiler provided by the Gadget Renesas Project. The GR-COTTON board comes mounted with a very small microcontroller (MCU). By programming this IC, you can make lights flash, emit various noises and trigger objects to move!

This reference describes libraries for writing programs for the GR-COTTON board and HTTP API for controlling the web compiler.

The GR-COTTON board is compatible with Arduino, with the libraries being nearly the same. The only key difference is, in Arduino, programs are called "sketches". For simplicity, we call a programs "sketches" for GR-COTTON as well.

Here's a little explanation about sketches. Take a look at the sample sketch below. This is a simple sketch that turns on a red LED on the GR-COTTON board.

#include <Arduino.h>
void setup(){
    pinMode(22, OUTPUT);
}
 
void loop(){
    digitalWrite(22, HIGH);
    delay(200);
    digitalWrite(22, LOW);
    delay(200);
}

Arduino requires a unique description, setup() and loop(), to be included in the sketch. The setup() function is called only once after reset or power-on. Then, the loop() function is executed repeatedly. For example, the sketch to the right turns the LED on and off the using pinMode(), digitalWrite(), and delay() functions. The pinMode() in the setup() defines which pin to use for driving the LED. Then, the digitalWrite() turns the LED on and off. The delay() defines on and off time. When using the GR-COTTON board, always describe #include <RLduino78.h>, the library that includes all these Arduino compatible functions, in the first line.

The best thing about Arduino is its plentiful choice of libraries. These libraries make it easy to not only turn on LEDs, but also emit noises, run motors and connect to networks. Check out the lineup in the LIBRARY tab from the menu above.

The image below describes the pin layout for the GR-COTTON board. There are many cases where you will use the library with a pin number. For example, the following description:

digitalWrite(2, LOW);

This means to set pin2 to LOW. And, from A0 to A7 can be used to read an analog value. For example, the following description:

analogRead(A0);

March 30, 2018: Updated Serial and Ethernet. Added SoftwareSerial.

        #include <Arduino.h>
        void setup() 
        { 
          Serial.begin(9600);
          Serial.println("Hello");
        } 
        

        #include <Arduino.h>
        #include <servo.h> 
          
        Servo servo0;
        void setup() 
        { 
          servo0.attach(9);
          servo0.write(90);  // set servo to mid-point
        } 
        

Feel free to go to the Renesas Engineering Community with questions, problems or comments. Other users, both veterans and newbies, are there to help!