# StartHardware – Tutorials for Arduino

Arduino, Electronics, Fun

## Unit 20 – My digital cat 2/2

Let’s program our digital cat. It’s still a way to go.

We have to teach the digital pet some things. It should blink with the eyes (LEDs). It should purr when it’s stroked. It should grumble when it is ignored. Let’s start with the blinking.

Blinking eyes is actually not that different from the blinking LED example we discussed in the very beginning of that course. The LEDs can be connected to two digital Arduino pins. That means we need the commands pinMode and digitalWrite twice. The code could look like that:

``````int ledPin1 = 10;
int ledPin2 = 11;

void setup() {
pinMode(ledPin1, OUTPUT);
pinMode(ledPin2, OUTPUT);
}

void loop() {
digitalWrite(ledPin1, HIGH);
digitalWrite(ledPin2, HIGH);
delay(5000);
digitalWrite(ledPin1, LOW);
digitalWrite(ledPin2, LOW);
delay(50);
}``````

Now, both LED blink always in in the same speed. That is a bit boring, no? We should randomly blink the LEDs. Fortunately, there is a random-command.

### Info: random();

The random(maximum)-command creates a random number between 0 and the as argument given number (maximum). This number is never reached. If you write random(5) the random results are 0, 1, 2, 3 and 4.

Let’s generate a random number between 0 and 500. The eyes (LEDs) should switch off when the random number equals 1. That will create random intervals for eye blinking. Now, we put in a small delay at the end of the program. That will give us the needed break to see, that there is something really happening.

``````int ledPin1 = 10;
int ledPin2 = 11;

void setup() {
pinMode(ledPin1, OUTPUT);
pinMode(ledPin2, OUTPUT);
}

void loop() {
// LEDs on
digitalWrite(ledPin1, HIGH);
digitalWrite(ledPin2, HIGH);

if (random(500)==1){
digitalWrite(ledPin1, LOW);
digitalWrite(ledPin2, LOW);
delay(50);
}

delay(10);
}``````

### Purring

The digital pet should purr when it is stroked. To detect if it is stroked, we will use a digital sensor inside. When you stroke it, your hand will cover up some light and the sensor can detect that.

But at first Arduino hast to measure the normal light when the pet is not stroked. It can do it when it is connected to the USB but we have to code it. Let’s store that value into the variable lightNormal: lightNormal=analogRead(sensorPin);

The variable sensorThreshold is used to calibrate the brightness difference when it should start to purr. That is done with if(analogRead(sensorPin)> lightNormal + sensorThreshold){…}. It may be that you have to change the value. Just try out other values if it doesn’t purr.

That is the code without blinking eyes:

``````int sensorPin = 0;
int sensorThreshold = 20;

int lightNormal;

void setup() {
}

void loop() {
// Schnurren
tone(speakerPin,0.001);
} else {
noTone(speakerPin);
}

delay(10);
}``````

### Grumble

But what if nobody plays with the pet? When it is ignored for to long, it will play a little melody to get attention. We do it like we did with he blinking eyes. We use a random command. Of course, the pet must not grumble while it is stroked. So we have to connect two conditions. We can do that in the if-statement using the double et-sign (&&).

``````int sensorPin = 0;
int sensorThreshold = 20;

int speakerPin = 9;

int lightNormal;

void setup() {
}

void loop() {

// Meckern
tone(speakerPin,1200);
delay(100);
tone(speakerPin,800);
delay(200);
tone(speakerPin,1000);
delay(200);
tone(speakerPin,1200);
delay(100);
}

delay(10);
}``````

If your digital pet should grumble or not is of course up to you 😉

Here you can find the complete code for the digital pet:

``````int ledPin1 = 10;
int ledPin2 = 11;

int sensorPin = 0;
int sensorThreshold = 20;

int speakerPin = 9;

int lightNormal;

void setup() {
pinMode(ledPin1, OUTPUT);
pinMode(ledPin2, OUTPUT);

}

void loop() {
// LEDs on
digitalWrite(ledPin1, HIGH);
digitalWrite(ledPin2, HIGH);

if (random(500)==1){
digitalWrite(ledPin1, LOW);
digitalWrite(ledPin2, LOW);
delay(50);
}

// purring
tone(speakerPin,0.001);
} else {
noTone(speakerPin);
}

// grumbling
tone(speakerPin,1200);
delay(100);
tone(speakerPin,800);
delay(200);
tone(speakerPin,1000);
delay(200);
tone(speakerPin,1200);
delay(100);
}

delay(10);
}``````

Wow! That was complicated. Time to tinker something!