1 Pin & 6 Buttons - Analog Keyboard

• We can use a microprocessor with more pins.
• We can use i2c, one-wire, UART ( How to use ESP8266 with PCF8574 - 4 input and 4 output).
• We can use the encoder ( Arduino PWM LED dimmer - 6x10W LED)
• Or we can use an analog keyboard.

This article can also see here:

1 pin & 6 buttons - Analog Keyboard

Components I used in this example.

• Arduino mini pro
• Buttons switch
• 6 x Resistors 1k ohm
• OLED i2c dispaly
• Some wires

Connection of analog keyboard to Arduino.

The method to read the key is very simple. Each key gives different output voltage so using the analog-digital converter recognize which key was pressed. Because reading from the analog input may be slightly different, it is safe to check whether the value is in the range.

#define CHECK_KEY( __v0__, __v1__) __v0__ >= (__v1__ - 10) && __v0__ < (__v1__ + 10)

byte GetKeyNumber(int key){
  byte num = 255;
  
  //0, 90, 170, 236, 293, 340
  if( key < 10 ){
    num = 0;
  }else if( CHECK_KEY(key, 90) ){
    num = 1;
  }else if( CHECK_KEY(key, 170) ){
    num = 2;
  }else if( CHECK_KEY(key, 236) ){
    num = 3;
  }else if( CHECK_KEY(key, 293) ){
    num = 4;
  }else if( CHECK_KEY(key, 340) ){
    num = 5;
  }
  return num;
}