knockbox.ino

/* Detects patterns of knocks and replies

    By Paul Mandel http://www.mand3l.com/work/#knock-box

    Adapted from code by Steve Hoefer http://grathio.com
    Version 0.1.10.20.10
    Licensed under Creative Commons Attribution-Noncommercial-Share Alike 3.0
    http://creativecommons.org/licenses/by-nc-sa/3.0/us/
    (In short: Do what you want, just be sure to include this line and the four above it, and don't sell it or use it in anything you sell without contacting me.)
 */

// Pin definitions
const int knockSensor = 0;                 // Piezo sensor on pin 0.
const int knockOverride = 6;             // Button to override if piezo not available
const int programSwitch = 2;             // If this is high we program a new code.
const int lockMotor = 3;                     // Gear motor used to turn the lock.
const int redLED = 4;                            // Status LED
const int greenLED = 5;                        // Status LED
const int playbackLED = 13;                 // Indicator LED to play back knock pattern
const int playbackSpeaker = 7;           // Speaker to play back knock pattern

// Tuning constants.    Could be made vars and hoooked to potentiometers for soft configuration, etc.
const int threshold = 3;                     // Minimum signal from the piezo to register as a knock
const int rejectValue = 50;                // If an individual knock is off by this percentage of a knock we don't unlock..
const int averageRejectValue = 50; // If the average timing of the knocks is off by this percent we don't unlock.
const int knockFadeTime = 100;         // milliseconds we allow a knock to fade before we listen for another one. (Debounce timer.)
const int knockPlaybackTime = 50;      // millisecnds we play back a knock for.
const int lockTurnTime = 650;            // milliseconds that we run the motor to get it to go a half turn.

const int maximumKnocks = 20;             // Maximum number of knocks to listen for.
const int knockComplete = 1200;         // Longest time to wait for a knock before we assume that it's finished.
const int knockReset = 300;


// Variables.
int shaveAndAHaircut[maximumKnocks] = {50, 50, 25, 50, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};    // Initial setup: "Shave and a Hair Cut, two bits."
int response[maximumKnocks] = {400, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};   // Standard response to "shave and a haircut"
int knockReadings[maximumKnocks];     // When someone knocks this array fills with delays between knocks.
int knockSensorValue = 0;                     // Last reading of the knock sensor.
int knockOverrideValue = 0;                   // Last reading of the knock override sensor
int programButtonPressed = false;     // Flag so we remember the programming button setting at the end of the cycle.

void setup() {
    pinMode(lockMotor, OUTPUT);
    pinMode(redLED, OUTPUT);
    pinMode(greenLED, OUTPUT);
    pinMode(programSwitch, INPUT);

    pinMode(knockOverride, INPUT);
    digitalWrite(knockOverride, HIGH);

    pinMode(playbackLED, OUTPUT);
    digitalWrite(playbackLED, LOW);

    Serial.begin(9600);                             			// Uncomment the Serial.bla lines for debugging.
    Serial.println("Program start.");    			// but feel free to comment them out after it's working right.

    digitalWrite(greenLED, HIGH);            // Green LED on, everything is go.
}

void loop() {
    // Listen for any knock at all.
    knockSensorValue = analogRead(knockSensor);
    knockOverrideValue = digitalRead(knockOverride);

/*
    if (digitalRead(programSwitch)==HIGH){    // is the program button pressed?
        programButtonPressed = true;                    // Yes, so lets save that state
        digitalWrite(redLED, HIGH);                     // and turn on the red light too so we know we're programming.
    } else {
        programButtonPressed = false;
        digitalWrite(redLED, LOW);
    }
*/
    if (knockSensorValue >=threshold){
        listenToSecretKnock();
    }
}

// Records the timing of knocks.
void listenToSecretKnock(){
    Serial.println("knock starting");

    // First lets reset the listening array.
    for (int i = 0;i<maximumKnocks;i++){
        knockReadings[i]=0;
    }

    int currentKnockNumber=0;                 			// Incrementer for the array.
    int startTime=millis();                     			// Reference for when this knock started.
    int now=millis();

    delay(knockFadeTime);

    do {
        //listen for the next knock or wait for it to timeout.
        knockSensorValue = analogRead(knockSensor);
        knockOverrideValue = digitalRead(knockOverride);

        if (knockSensorValue >=threshold){                                     //got another knock...
            //record the delay time.
            Serial.println("knock.");
            now=millis();
            knockReadings[currentKnockNumber] = now-startTime;
            currentKnockNumber ++;                                                         //increment the counter
            startTime=now;
            // and reset our timer for the next knock
            digitalWrite(greenLED, LOW);
            if (programButtonPressed==true){
                digitalWrite(redLED, LOW);                                             // and the red one too if we're programming a new knock.
            }
            delay(knockFadeTime);                                                            // again, a little delay to let the knock decay.
            digitalWrite(greenLED, HIGH);
            if (programButtonPressed==true){
                digitalWrite(redLED, HIGH);
            }
        }

        now=millis();

        //did we timeout or run out of knocks?
    } while ((now-startTime < knockComplete) && (currentKnockNumber < maximumKnocks));
    Serial.println('Finished recording knock');

    if (matchKnock()) {
        for (int i=0;i<maximumKnocks;i++) {
            knockReadings[i] = response[i];
        }
    }

    // We've got our knock recorded, let's play it back.
    Serial.println('playback starting');
    for (int i=0;i<currentKnockNumber+1;i++) {
        digitalWrite(playbackLED, HIGH);
        delay(knockPlaybackTime);
        digitalWrite(playbackLED, LOW);
        if (knockReadings[i] > 0) {
            delay(knockReadings[i] - knockPlaybackTime);
        } else {
            delay(knockReset);
            break;
        }
    }
    Serial.println('Done with playback');
}


// Runs the motor (or whatever) to unlock the door.
void triggerDoorUnlock(){
    Serial.println("Door unlocked!");
    int i=0;

    // turn the motor on for a bit.
    digitalWrite(lockMotor, HIGH);
    digitalWrite(greenLED, HIGH);                        // And the green LED too.

    delay(lockTurnTime);                                        // Wait a bit.

    digitalWrite(lockMotor, LOW);                        // Turn the motor off.

    // Blink the green LED a few times for more visual feedback.
    for (i=0; i < 5; i++){
            digitalWrite(greenLED, LOW);
            delay(100);
            digitalWrite(greenLED, HIGH);
            delay(100);
    }

}

// Sees if our knock matches the secret.
// returns true if it's a good knock, false if it's not.
// todo: break it into smaller functions for readability.
boolean matchKnock(){
    int i=0;

    // simplest check first: Did we get the right number of knocks?
    int currentKnockCount = 0;
    int secretKnockCount = 0;
    int maxKnockInterval = 0; 			// We use this later to normalize the times.

    for (i=0;i<maximumKnocks;i++){
        if (knockReadings[i] > 0){
            currentKnockCount++;
        }
        if (shaveAndAHaircut[i] > 0){					//todo: precalculate this.
            secretKnockCount++;
        }

        if (knockReadings[i] > maxKnockInterval){	// collect normalization data while we're looping.
            maxKnockInterval = knockReadings[i];
        }
    }

    if (currentKnockCount != secretKnockCount){
        return false;
    }

    // Now we compare the relative intervals of our knocks, not the absolute time between them.
    // (ie: if you do the same pattern slow or fast it should still open the door.)
    // This makes it less picky, which while making it less secure can also make it
    // less of a pain to use if your tempo is a little slow or fast.

    int totaltimeDifferences=0;
    int timeDiff=0;
    for (i=0;i<maximumKnocks;i++){ // Normalize the times
        int knockReadingsi = map(knockReadings[i],0, maxKnockInterval, 0, 100);
        timeDiff = abs(knockReadingsi-shaveAndAHaircut[i]);
        if (timeDiff > rejectValue){ // Individual value too far out of whack
            return false;
        }
        totaltimeDifferences += timeDiff;
    }
    // It can also fail if the whole thing is too inaccurate.
    if (totaltimeDifferences/secretKnockCount>averageRejectValue){
        return false;
    }

    return true;

}