Adding more is the next step. We're going to go over what you need to do to modify and extend an Arduino sketch.
reopen and modify the blink sketch like you did in lesson 1 if you have shut down the IDE, then where it now says
int led = A0;
you need to add more lines:
int led = A0;
int led2 = A1; // second LED
int led3 = A2; // third LED
and you need to set the pin mode for where we're going to connect the LEDs, so go to void setup(), and modify it.
pinMode(led, OUTPUT);
pinMode(led2, OUTPUT);
pinMode(led3, OUTPUT);
and finally you need to modify the content of void loop() from this:
digitalWrite(led, HIGH);
delay(1000);
digitalWrite(led, LOW);
delay(1000);
to this:
digitalWrite(led, HIGH); // turn on LED1
delay(1000);
digitalWrite(led, LOW); // then turn it off
digitalWrite(led2, HIGH); // and turn on LED2
delay(1000);
digitalWrite(led2, LOW); // then turn it off
digitalWrite(led3, HIGH); // and turn on LED3
delay(1000);
digitalWrite(led3, LOW); // then turn it off
Notice we don't add a delay between setting led to LOW and setting led2 to HIGH. This is because we want the second LED to light up as soon as the first one has gone out, making it look like the light is moving from one LED to another.
Add another two LEDs with their anodes (positive legs) in A1 and A2. Upload the sketch and you should see the three LEDs light up in sequence.
Whenever you add a new output to your sketch, you need to make sure you set the pinMode for the pin you are going to be using. Usually, you want to setup some int values for the pins so it is a little easier to know what each pin is for. You have to use digitalWrite to set whether the pin is outputting a GND (LOW) or VCC (HIGH) value.
We're limited to only having 6 LEDs when powering them directly from the pins. There are a number of different ways around this limit, but the one we will be exploring later involves adding another chip to the setup, a shift register, and that will let us power 8 (or even more) LEDs from only three pins.