keypadResistanceLookupRobotDun4x4AnalogOut.ino

// BETLOG - 2018-10-18
// mean/average based lookup tables for the RobotDyn 4x4 key 1 analog out pin keypad
#define         PIN_KB_IO           A0
unsigned long   LIMIT_freq        = 20;
unsigned long   LIMIT_keyRepeat   = 1000;
const char KEY_ARRAY[]= {
    '1','2','3','4',
    '5','6','7','8',
    '9','0','A','B',
    'C','D','E','F'
};
int OHMS_ARRAY[]= {
    1023,930,850,790,
    680,640,600,570,
    512,487,465,445,
    410,330,277,238
};
//-----
int             KEY_ARRAY_SIZE  = sizeof(KEY_ARRAY);
int             MID_ARRAY[sizeof(KEY_ARRAY)];
char            keyValueIs = "";
char            keyValueWas = "";
unsigned long   nowWas;
unsigned long   nowIs;
unsigned long   keyPressedTime;
int             messageState = 0;
int analogValue;
int i;
int target;
int upper;
int lower;
//-------------------
void setup(){
    pinMode(PIN_KB_IO, INPUT);
    for(i=0; i<=sizeof(KEY_ARRAY)-1; i++){
        MID_ARRAY[i]=OHMS_ARRAY[i]-( ( OHMS_ARRAY[i]-OHMS_ARRAY[i+1] ) /2);
    }
    nowWas = keyPressedTime  = millis();
    Serial.begin(9600);
    Serial.println("READY");
}
void loop(){
    analogValue = analogRead(PIN_KB_IO);
    if ( analogValue > 200 ){
        nowIs= millis();
        if( nowIs > nowWas + LIMIT_freq ){
            nowWas = nowIs;
            for(i=0; i<KEY_ARRAY_SIZE; i++){
                target= OHMS_ARRAY[i];
                lower= MID_ARRAY[i];
                upper= MID_ARRAY[i-1];
                if ( i == 0 ){
                    upper=target;
                } else if ( i == KEY_ARRAY_SIZE ){
                    lower=target;
                }
                if ( analogValue >= lower && analogValue <= upper ){
                    keyValueIs = KEY_ARRAY[i];
                    if ( messageState == 0 ){
                        Serial.print(keyValueIs);
                        Serial.print(" :PRESSED.. ");
                        messageState = 1;
                        keyPressedTime = nowIs;
                        }
                    } else if ( messageState == 1 ){
                        if ( nowIs > keyPressedTime + LIMIT_keyRepeat ){
                            Serial.print(" ..HELD.. ");
                            messageState = 2;
                        }
                    }
                    break;
                }
            }
        }
    } else if ( messageState != 0 ) {
        Serial.println(" ..RELEASED");
        keyValueIs = "";
        messageState = 0;
        keyPressedTime = 0;
    }
}