int adc_key_val [5] = {50, 200, 400, 600, 800};

int NUM_KEYS = 5;

int adc_key_in;

int key = -1;

int oldkey = -1;

void setup ()

{

pinMode (13, OUTPUT); / / we\`ll use the debug LED to output a heartbeat

Serial.begin (9600); / / 9600 bps

}

void loop ()

{

adc_key_in = analogRead (0); / / read the value from the sensor

digitalWrite (13, LOW);

key = get_key (adc_key_in); / / convert into key press

if (key! = oldkey) / / if keypress is detected

{

delay (50); / / wait for debounce time

adc_key_in = analogRead (0); / / read the value from the sensor

key = get_key (adc_key_in); / / convert into key press

if (key! = oldkey)

{

oldkey = key;

if (key> = 0) {

digitalWrite (13, HIGH);

switch (key)

{

case 0: Serial.println ("S1 OK");

break;

case 1: Serial.println ("S2 OK");

break;

case 2: Serial.println ("S3 OK");

break;

case 3: Serial.println ("S4 OK");

break;

case 4: Serial.println ("S5 OK");

break;

}

}

}

}

delay (100);

}

/ / Convert ADC value to key number

int get_key (unsigned int input)

{

int k;

for (k = 0; k

{

if (input

{

return k;

}

}

if (k> = NUM_KEYS) k = -1; / / No valid key pressed

return k;

}