1. IoT
Programming the Particle Photon

2. Cloud Service
sensor
Browser
actuator
Photon

4. Pins Input Pin - reads voltage at that point in the circuit
Output Pin - allows voltage to flow out from that point in the circuit
Can be digital or analog

5. build.particle.io/ Build: Web IDE
Flash
Verify
Save

6. Build: Web IDE
Code
Library
Docs
Devices
Settings

7. New App:
void setup() { }
void loop() {

8. C stuff Define stuff before you use it. Arrays:
int[] nums = {1,2,3,4};
Constants:
Use “const” (not “final”)

9. C(++) Strings
Photons let you use Strings and some String functions like you’re used to:
String message = “message”;
You should know that underneath it is an array of characters with a null character at the end.

10. C Characters char letter = ‘c’; But chars are really ints.
int index = ‘c’ - ‘a’; // index is now 2.
if (letter >= ‘a’ && letter <= ‘z’) // if lowercase letter

11. Pointers Every variable has a name, a value, and a memory address.
Consider:
int x = 3;
&x refers to the address of variable x.

12. Pointers
To store the address of a variable, you need a pointer type. Declare variables with a star:
int x = 3;
int* ptr = &x;

13. Pointers
If you have a pointer variable, you can retrieve the value of the variable it points to.
int x = 3;
int* ptr = &x;
int y = *ptr; // What’s the value of y?

14. int x = 3; int* ptr = &x; int y = *ptr; ADD NAME TYPE VALUE 1000 x int
2000
ptr
int*
3000 y

15. int x = 3; int* ptr = &x; int y = *ptr; ADD NAME TYPE VALUE 1000 x int
2000
ptr
int*
3000 y

16. int x = 3; int* ptr = &x; int y = *ptr; ADD NAME TYPE VALUE 1000 x int
2000
ptr
int*
3000 y

17. Photon stuff
There are constants (ints) named after the pins and also for INPUT, OUTPUT, HIGH, LOW, …
Spark.function
Spark.variable
Be careful with the terminology

18. Hello World void setup(){ RGB.control(true); } void loop(){
RGB.color(255,0,0);
delay(2000); RGB.color(0,255,0);
delay(2000);
RGB.color(0,0,255);
delay(2000); }

19. Let’s add a light

20. Controlling the light int ledPin = D7; void setup(){
pinMode(ledPin, OUTPUT); }
...
digitalWrite(ledPin, HIGH); // light on
delay(1000); // wait one second
digitalWrite(ledPin, LOW); // light off

21. Input: Switches Use a pin as digital input.
Can be either a pull-up or pull-down (or neither, technically)

22. Pull-down Switch sits between the input pin and the voltage source.
Switch off = Low voltage
to input pin

23. Pull-down Issue with pull-down:
What if circuit is built with pin still in output
mode?
Can cause a short circuit before the code is flashed.

24. Pull-up Switch sits between pin and ground.
Switch off = High voltage reading
We generally use this as it is safer.

25. I/O!!
D7 -> 220R -> LED-> GND
D3 -> SWITCH-> GND

26. Code int ledPin = D7; int switchPin = D3; void setup(){
pinMode(ledPin, OUTPUT);
pinMode(switchPin, INPUT_PULLUP); }
void loop(){
if(digitalRead(switchPin) == LOW){ // Button is pressed
digitalWrite(ledPin,HIGH);
else{
digitalWrite(ledPin, LOW);
} }

27. Code Design
Write a Morse code flasher. When you press the button the flashing begins.
What are the variables? Functions?
How will we write it?

28. Before you go for it... String letters[] = {
".-", "-...", "-.-.", "-..", ".", "..-.", "--.", "....", "..", // A-I
".---", "-.-", ".-..", "--", "-.", "---", ".--.", "--.-", ".-.", // J-R
"...", "-", "..-", "...-", ".--", "-..-", "-.--", "--.." // S-Z };
Timing:
Dot: 200
Dash: 600
Between dots and dashes: 200
Between letters of a word: 400
Between words: 1400
Between messages: 5000

29. Analog Input The A0-A5 pins can be used for analog input.
They give a value from , telling how much voltage is at that point.

30. Analog Output Pin DAC (Digital-to-Analog converter)
gives true analog output
Other A pins (A4 & A5) give “fake” analog output using Pulse Width Modulation
Analog outputs are between 0 and 255

32. Code setup is same as before - tell what is input and what is output.
digitalRead becomes analogRead
digitalWrite becomes analogWrite

33. Try a program Set up A5 as an analog output.
Connect A5 -> 220 Resistor -> LED -> Ground
Set up A0 as an analog input.
Connect 3V3 -> Photoresistor -> A0 -> 1K Resistor -> Ground
Program: The darker the sensor, the brighter the LED.
(Note: Is very sensitive. Try different things. I divided by 500?????)