Controlling multiple buttons with only one Arduino's analog port

Sometimes when we need to handle a set of buttons it may take most part of digital ports and limit the device capabilities. In these cases that we don't have enough available digital ports, a good solution is to use an analog port to handle a series of buttons and resistors.

Versão em português desse artigo: Controlando mútiplos botões com somente uma porta analógica do Arduino.

The ebl-arduino's ButtonEvent class is now capable to handle series of analog buttons. Consider the following breadboard project:

Note that it's a 10k resistors series. Click here to download the Fritzing source file for this project.

In order to handle these buttons you should proceed as the source code bellow:

#include <ButtonEvent.h>

short Button1 = 230;
short Button2 = 365;
short Button3 = 460;

void setup() {
  //initial buffer for 3 buttons
  ButtonEvent.initialCapacity = sizeof(ButtonInformation)*3;

  ButtonEvent.addButton(0,        //analog button pin
                        Button1,  //analog value
                        20,       //deviation
                        onDown,   //onDown event function
                        onUp,     //onUp event function
                        onHold,   //onHold event function
                        1000,     //hold time in milliseconds
                        onDouble, //onDouble event function
                        200);     //double time interval

  ButtonEvent.addButton(0,        //analog button pin
                        Button2,  //analog value
                        20,       //deviation
                        onDown,   //onDown event function
                        onUp,     //onUp event function
                        onHold,   //onHold event function
                        1000,     //hold time in milliseconds
                        onDouble, //onDouble event function
                        200);     //double time interval

  ButtonEvent.addButton(0,        //analog button pin
                        Button3,  //analog value
                        20,       //deviation
                        onDown,   //onDown event function
                        onUp,     //onUp event function
                        onHold,   //onHold event function
                        1000,     //hold time in milliseconds
                        onDouble, //onDouble event function
                        200);     //double time interval

  Serial.begin(9600);
}


void loop() {
  ButtonEvent.loop();
}

void onDown(ButtonInformation* Sender) {
  Serial.print("Button ");

  if (Sender->analogValue == Button1)
    Serial.print(1);
  else if (Sender->analogValue == Button2)
    Serial.print(2);
  else if (Sender->analogValue == Button3)
      Serial.print(3);

  Serial.println(" down!");
}

void onUp(ButtonInformation* Sender) {
  Serial.print("Button ");

  if (Sender->analogValue == Button1)
    Serial.print(1);
  else if (Sender->analogValue == Button2)
    Serial.print(2);
  else if (Sender->analogValue == Button3)
      Serial.print(3);

  Serial.println(" up!");
}

void onHold(ButtonInformation* Sender) {
  Serial.print("Button ");

  if (Sender->analogValue == Button1)
    Serial.print(1);
  else if (Sender->analogValue == Button2)
    Serial.print(2);
  else if (Sender->analogValue == Button3)
      Serial.print(3);

  Serial.print(" hold for ");
  Serial.print(Sender->holdMillis);
  Serial.println("ms!");
}

void onDouble(ButtonInformation* Sender) {
  Serial.print("Button ");

  if (Sender->analogValue == Button1)
    Serial.print(1);
  else if (Sender->analogValue == Button2)
    Serial.print(2);
  else if (Sender->analogValue == Button3)
      Serial.print(3);

  Serial.print(" double click in ");
  Serial.print(Sender->doubleMillis);
  Serial.println("ms!");
}

This project has their own repository with more information about the classes, usage instructions and download options. It could be accessed through the URL http://code.google.com/p/ebl-arduino/.