DESCRIPTION
The Kimat One Wire Keypad module instantly simplifies the implementation of a 4×4 or 3×4 keypad matrix. It uses just one analog pin as opposed to 7 or 8 pins without this module. It utilizes an array or resistors carefully chosen to allow unique voltage output for each keypress. It is then read by the
microcontroller/Arduino ADC (analog) pins for decoding.

FEATURES and SPECIFICATIONS

> Simplifies Connections. One 3 lines required: an analog line, a 5V and a Ground line
> Saves 6-7 IO pins
> Plugs directly into the keypad.
> Supports the common dome matrix 4×4 and 3×4 keypads
> Arduino Compatible
> Simple analog voltage output with distinct level for each key
> Library available

Kimat One Wire Keypad Module Pin	Module Pin Function
VCC	Connects to the 5V pin of the Arduino
AN	The analog voltage output. Connects to an analog input pin (ADC)
GND	Ground
KEYPAD 1-8	Connects to the keypad matrix

LIBRARY
We have adopted Andrew Mascolo Jr’s OnewireKeypad library:
https://github.com/AndrewMascolo/OnewireKeypad
We have tweaked the example to work specifically for the Kimat One Wire Keypad Module:

Example Code Using Library

#include <OnewireKeypad.h> 
char KEYS[] = { 
'1', '2', '3', 'A', 
'4', '5', '6', 'B', 
'7', '8', '9', 'C', 
'*', '0', '#', 'D' 
}; 
Kimat One Wire Keypad Module 
User Guide 
OnewireKeypad <Print, 16 > KP2(Serial, KEYS, 4, 4, A0, 4700, 1000, 10000, ExtremePrec ); 
void setup () { 
Serial.begin(115200); 
// This method is set in the constructor with a default value of 5.0 
// You only need to include this method if your Arduino is not supplying 5v to 
// the keypad. ie. ~4.7v or even with 3.3v Arduino boards too. 
//KP2.SetKeypadVoltage(5.0); 
KP2.SetKeypadVoltage(4.95); 
} 
void loop() 
{ 
if ( char key = KP2.Getkey() ) { 
switch (KP2.Key_State()) { 
case PRESSED: 
Serial << "Key: " << key << " State: "; 
Serial.println("PRESSED"); 
break; 
case RELEASED: 
Serial << "Key: " << key << " State: "; 
Serial.println("RELEASED"); 
break; 
case HELD: 
Serial << "Key: " << key << " State: "; 
Serial.println("HOLDING"); 
break; 
} 
} 
} 

Example Code with 16×2 LCD (I2C)

EXAMPLE CODE WITH 16x2 LCD 
Kimat One Wire Keypad Module 
User Guide 
#include <Wire.h> 
#include <LiquidCrystal_I2C.h> 
#include <OnewireKeypad.h> 
char KEYS[] = { 
'1', '2', '3', 'A', 
'4', '5', '6', 'B', 
'7', '8', '9', 'C', 
'*', '0', '#', 'D' 
}; 
LiquidCrystal_I2C lcd(0x3F,16,2); 
OnewireKeypad <Print, 16 > KP2(Serial, KEYS, 4, 4, A0, 4700, 1000, 10000, ExtremePrec ); 
void setup () { 
Serial.begin(115200); 
lcd.init(); 
lcd.backlight(); 
// This method is set in the constructor with a default value of 5.0 
// You only need to include this method if your Arduino is not supplying 5v to 
// the keypad. ie. ~4.7v or even with 3.3v Arduino boards too. 
//KP2.SetKeypadVoltage(5.0); 
KP2.SetKeypadVoltage(4.95); 
lcd.setCursor(0,0);lcd.print(" LAYAD CIRCUITS "); 
lcd.setCursor(0,1);lcd.print("LC 1-WIRE KEYPAD"); 
delay(2000); 
lcd.clear(); 
} 
void loop() 
{ 
if ( char key = KP2.Getkey() ) { 
switch (KP2.Key_State()) { 
case PRESSED: 
lcd.clear(); 
lcd.setCursor(0,0);lcd.print("LC 1-WIRE KEYPAD"); 
lcd.setCursor(2,1);lcd.print(key); 
lcd.setCursor(4,1);lcd.print(": PRESSED"); 
Serial.print(key); 
Serial.println(" PRESSED"); 
break; 
case RELEASED: 
lcd.clear(); 
lcd.setCursor(0,0);lcd.print("LC 1-WIRE KEYPAD"); 
lcd.setCursor(2,1);lcd.print(key); 
lcd.setCursor(4,1);lcd.print(": RELEASED"); 
Serial.print(key); 
Serial.println(" RELEASED"); 
break; 
case HELD: 
lcd.clear(); 
lcd.setCursor(0,0);lcd.print("LC 1-WIRE KEYPAD"); 
lcd.setCursor(2,1);lcd.print(key); 
lcd.setCursor(4,1);lcd.print(": HOLDING"); 
Serial.print(key); 
Serial.println(" HOLDING"); 
break; 
} 
} 
} 

Example Using Raw ADC values

Note: ADC values should be tuned on every individual circuit

const bool LC_KIMAT1WIRE_4x4 = 0;
const bool LC_KIMAT1WIRE_3x4 = 1;
const bool kpsize = LC_KIMAT1WIRE_3x4; // LC_KIMAT1WIRE_4x4 for 4x4 or LC_KIMAT1WIRE_3x4 for 3x4
const unsigned int KIMAT1WIRE_PIN = A1; // define the Arduino pin connected to AO

unsigned int rawadc;// ADC value
char key; // last key pressed
char lastkey; // previous key

void setup() {
  Serial.begin(9600);
  Serial.println(F("Press a Key to Print raw ADC value and decoded key"));
}

void loop() {

  rawadc = 0;
  for(byte i=0;i<10;i++)
  {
    rawadc += analogRead(KIMAT1WIRE_PIN);
  }
  rawadc /= 10;

  if(kpsize == LC_KIMAT1WIRE_4x4) // 4x4 keypad
  {
    // adjust the ADC raw values below according to your reading
    if(rawadc >= 1008)     { key = '1'; }
    else if(rawadc >= 875) { key = '2'; }
    else if(rawadc >= 820) { key = '3'; }
    else if(rawadc >= 760) { key = 'A'; }
    else if(rawadc >= 683) { key = '4'; }
    else if(rawadc >= 620) { key = '5'; }
    else if(rawadc >= 590) { key = '6'; }
    else if(rawadc >= 560) { key = 'B'; }
    else if(rawadc >= 510) { key = '7'; }
    else if(rawadc >= 490) { key = '8'; }
    else if(rawadc >= 465) { key = '9'; }
    else if(rawadc >= 442) { key = 'C'; }
    else if(rawadc >= 425) { key = '*'; }
    else if(rawadc >= 400) { key = '0'; }
    else if(rawadc >= 380) { key = '#'; }
    else if(rawadc >= 375) { key = 'D'; }
    else
    {
      key = NULL;
    }
  }
  else // 3x4 keypad
  {
    if(rawadc >= 1009)     { key = '1'; }
    else if(rawadc >= 865) { key = '2'; }
    else if(rawadc >= 820) { key = '3'; }
    else if(rawadc >= 680) { key = '4'; }
    else if(rawadc >= 620) { key = '5'; }
    else if(rawadc >= 590) { key = '6'; }
    else if(rawadc >= 510) { key = '7'; }
    else if(rawadc >= 485) { key = '8'; }
    else if(rawadc >= 470) { key = '9'; }
    else if(rawadc >= 420) { key = '*'; }
    else if(rawadc >= 395) { key = '0'; }
    else if(rawadc >= 380) { key = '#'; }
    else
    {
      key = NULL;
    }
  }

  if(key && (key != lastkey))
  {
    Serial.print(F("Raw Value="));
    Serial.print(rawadc);
    Serial.print(F("\tDecoded Key="));
    Serial.println(key);
  }
  lastkey = key;



}