All of the code needed to run this project is located at
https://bitbucket.org/alterationx10/8bitbox-adafruit

The Arduino sketch is located (from the source root directory) at

/Arduino/_8BitBox_Adafruit/_8BitBox_Adafruit.ino

The code is fairly commented, and is best explained while looking right at it.

Some concepts are highlighted/discussed below, but you should check out the source for all the details.

Defining some Variables:

Here are the variables defined at the top of the sketch, and used throughout the code.

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// Define our pins
int buzzerPin = 3;  // Piezo buzzer is hooked to pwm 3
int redPin = 9;     // Red LED hooked to pwm 9
int greenPin = 10;  // Green LED hooked to pwm 10
int bluePin = 11;   // Blue LED hooked to pwm 11

int commandByte;   // A variable for command parsing

// We will store our favorite color in the EEPROM
// NOTE:
// From http://playground.arduino.cc/Code/EEPROM-Flash :
// "The ATmega328 has 32 KiB of Flash program memory. 
//  This memory supports at least 10,000 writes or upload cycles."
int FAV_RED = 0;
int FAV_GREEN = 1;
int FAV_BLUE = 2;

// Define our pins
int buzzerPin = 3;  // Piezo buzzer is hooked to pwm 3
int redPin = 9;     // Red LED hooked to pwm 9
int greenPin = 10;  // Green LED hooked to pwm 10
int bluePin = 11;   // Blue LED hooked to pwm 11

int commandByte;   // A variable for command parsing

// We will store our favorite color in the EEPROM
// NOTE:
// From http://playground.arduino.cc/Code/EEPROM-Flash :
// "The ATmega328 has 32 KiB of Flash program memory. 
//  This memory supports at least 10,000 writes or upload cycles."
int FAV_RED = 0;
int FAV_GREEN = 1;
int FAV_BLUE = 2;

Defining some Functions:

Setting an LED:

Here is a snippet of a function used to set the value of the Red LED (similar functions are made for the G and B). Note that we use a common anode RGB LED, so we use analogWrite(pin, 255 - colorValue)!

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// Set the PWM of the Red LED
void setRed(int val) {
  // Sanitize the value
  if (val > 255) {
    val = 255;
  }
  if (val < 0) {
    val = 0;
  }  
  analogWrite(redPin, 255 - val);
}

// Set the PWM of the Red LED
void setRed(int val) {
  // Sanitize the value
  if (val > 255) {
    val = 255;
  }
  if (val < 0) {
    val = 0;
  }  
  analogWrite(redPin, 255 - val);
}

Making a blocking read:

Serial.read() will perform faster than we can send data to the Arduino, se we will need to know "how to speak" to the device using our own protocol. When we receive a known command of our protocol, we know there could be more data coming, so we need to do a blocking read to make sure we get it.

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// Serial.read() appears to go much faster than we can send text.
// Therefore, we add a method to do a blocking read.
int getNextByte() {
  while (Serial.available() == 0) {
    // BLOCK
  }
  return Serial.read();
}

// Serial.read() appears to go much faster than we can send text.
// Therefore, we add a method to do a blocking read.
int getNextByte() {
  while (Serial.available() == 0) {
    // BLOCK
  }
  return Serial.read();
}

The essential behavior of the sketch:

The loop() function of our sketch just checks to see if serial data is available, and if so, parse the command and perform an action.

Below is a snippet to show how it would parse for a command to set the Red LED to a certain value, using the two functions shown above.

In this example, we will send an "R" from the Android device as our protocol command to set the Red LED to a value, along with the value (0-255) to set it to.

If we receive an "R", then we know that there is one more byte on it's way as a value to set the LED to (0-255), so we then perform a blocking read to get it, and then use our function to set the value to the Red LED.

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void loop() {
  
   
  // All our loop currently does is check for serial data
  // and parse serial commands
  if (Serial.available() > 0) {
    
    // Read our command byte
    commandByte = Serial.read();
    // See if it matches any of our commands
   
    // Set the Red LED
    if (commandByte == 'R') {
      int redVal =  getNextByte();
      setRed(redVal);
    }
    
    // Parse for other commands in full sketch...
  }
}

void loop() {
  
   
  // All our loop currently does is check for serial data
  // and parse serial commands
  if (Serial.available() > 0) {
    
    // Read our command byte
    commandByte = Serial.read();
    // See if it matches any of our commands
   
    // Set the Red LED
    if (commandByte == 'R') {
      int redVal =  getNextByte();
      setRed(redVal);
    }
    
    // Parse for other commands in full sketch...
  }
}

This guide was first published on Jun 13, 2014. It was last updated on Jun 13, 2014.

This page (Arduino Code) was last updated on Jul 30, 2020.