The document provides an overview of building connected devices using the Electric Imp platform, which allows developers to connect microcontrollers to the internet and build applications involving hardware, firmware, web services and apps. It discusses what goes into an internet of things application and demonstrates how to get an imp device online, program digital and analog inputs/outputs, create HTTP handlers, and make HTTP requests to control devices from an agent.

1. Building Connected Things
with Electric Imp
These slides are licensed under the MIT License
http://opensource.org/licenses/MIT
SSID: impdemo
PW: electric
Matt Haines | Tom Byrne
matt@electricimp.com | tom@electricimp.com
@beardedinventor | @tlbyrn

2. Agenda
The Internet of Things
• What is the Internet of Things
• What does the Internet of Things space look like
• What goes into an Internet of Things application
• Overview of the Electric Imp platform
Workshop – Your first imp project
• Getting your first imp online
• Digital I/O
• Building a basic HTTPS request handler
• Making HTTP requests

3. The Internet of Things (2025)
50B
Connected
Devices
$6.2T
Economic
Impact
McKinsey Global Institute, 2013

4. Internet of Things Verticals

5. What Goes Into an IoT Application
• Hardware
• Microcontrollers, radios, sensors, actuators, etc
• Firmware
• Device logic, drivers, network stack, etc
• Server Code
• Heavy processing, external device API, data storage, etc
• External Web Services
• Weather APIs, Twitter, Twilio, Gmail/email, IFTTT, etc
• App / Website / Etc
• User interface, OAuth, etc
• Areas of knowledge required:
• Electrical Engineering, embedded software, security, backend/server
development, web development, database admin, app development, …

6. The Electric Imp Platform
Connectivity Infrastructure
In-house
Great products
Focus on the
core business
Platform
Server Infrastructure
In-house
Great products
Focus on the
core business
Platform

7. The Electric Imp Platform – Overview

8. The Electric Imp Platform - Devices
• 32-Bit ARM Cortex M3 processor
• 802.11 b/g/n WiFi
• Open WiFi, WEP, WPA, WPA2
• 80 KB* code space (device – 'firmware')
• 6/12 Configurable GPIO Pins
• Digital In/Out
• Analog In
• 12 bit DAC (Analog Out)
• PWM Out
• I2C, UART, SPI
* This value changes a little bit each release (the imp originally only had about 40 KB of code space)

9. The Electric Imp Platform - Agents
• Micro-server than can act on behalf of a device
• Runs on the Electric Imp Servers
• 1 MB code space
• 1MB RAM
• Allows you to do things that you typically can’t on an embedded processor
• Process incoming HTTP requests (create APIs for your device)
• Make outgoing HTTP requests (interact with external APIs)
• Persist small amounts of data

10. Let’s get started

11. BlinkUp - Getting Online
• Create an Electric Imp Account: https://ide.electricimp.com
• Download the Electric Imp mobile app:
• Android: play.google.com/store/apps/details?id=com.electricimp.electricimp
• iPhone: itunes.apple.com/us/app/electric-imp
• Sign into the app with your Electric Imp Account
• Enter WiFi credentials:
• SSID: impdemo
• PW: electric
• Power up your imp
• The imp’s internal LED must be blinking before continuing to the next step
• Click BlinkUp in the mobile app
• Hold screen of phone against blinking light of imp until BlinkUp is complete
• Your device should now be blinking green (online)*
* Your imp will stop blinking after 1 minute to save power (it is still powered on)

12. BlinkUp Example
* Your imp will stop blinking after 1 minute to save power (it is still powered on)

13. Creating a New Model

14. Creating a New Model

15. Creating a New Model

16. Creating a New Model

17. Digital Output - Circuit

18. Digital Output - Device Code
// Device Code
led <- hardware.pin9;
led.configure(DIGITAL_OUT);
state <- 0;
function blink() {
imp.wakeup(1.0, blink);
state = 1 – state;
led.write(state);
}
blink();

19. Blocking Loops are Bad!
// Device Code
// NOTE: THIS IS BAD CODE:
led <- hardware.pin9;
led.configure(DIGITAL_OUT);
function loop() {
local state = 0;
while (1) {
led.write(state);
state = 1 – state;
imp.sleep(1.0);
}
}
loop();

20. Digital Input – Circuit

21. Digital Input - Device Code
// Device Code:
led <- hardware.pin9;
led.configure(DIGITAL_OUT);
button <- hardware.pin1;
function onButton() {
local state = button.read();
led.write(state);
}
button.configure(DIGITAL_IN_PULLUP, onButton);

22. Event Driven Programming and Callbacks
• Squirrel is an Event Driven Language
• Behaviour is defined by events and callbacks
• An event is a pre-programmed thing that can happen:
• The timeout on an imp.wakeup ends
• The state of a DIGITAL_IN pin changes
• A message is passed from the device to the agent or vice versa
• An agent receives an incoming HTTP request
• A callback is a function bound to a event:
• imp.wakeup(5, blink);
• Tells the imp to run the function called blink in 5 seconds
• button.configure(DIGITAL_IN, onButton);
• Tells the imp to run the function called onButton when the state of the pin
assigned to button changes

23. HTTP Handlers
• Each device has an agent – a tiny micro servers that act on behalf of their device
• Each agent has a unique URL associated with it (see below)
• http.onrequest binds a callback to the 'received incoming HTTP Request' event

24. HTTP Handler – Agent Code
// Agent Code:
function httpHandler(request, response) {
if ("state" in request.query) {
local state = request.query["state"];
device.send("led", state);
}
response.send(200, "OK");
}
http.onrequest(httpHandler);

25. HTTP Handler – Device Code
// Device Code:
led <- hardware.pin9;
led.configure(DIGITAL_OUT);
function ledHandler(data) {
if (data == "0") {
server.log("LED OFF")
led.write(0);
} else {
server.log("LED ON");
led.write(1);
}
}
agent.on("led", ledHandler);

26. Passing Messages

27. Making HTTP Requests – Device Code
// Device Code:
led <- hardware.pin9;
led.configure(DIGITAL_OUT);
function ledHandler(data) {
if (data == "0") {
server.log("LED OFF")
led.write(0);
} else {
server.log("LED ON");
led.write(1);
}
}
agent.on("led", ledHandler);

28. Making HTTP Requests – Agent Code
// Add to the bottom of your agent code:
const URL = "https://agent.electricimp.com/RO5HOrveo4I1";
function buttonPressHandler(state) {
local url = URL + "?state=" + state;
local request = http.get(url);
request.sendasync(function(resp) {
server.log(resp.statuscode + " - " + resp.body);
});
}
device.on("buttonPress", buttonPressHandler)

29. Passing Messages

30. Other activities
• Device:
• Try to control your LED with PWM
• electricimp.com/docs/examples/pwm-led
• Bonus: Try to control the brightness with a web request
• Create multiple “states” for your LED (on, off, blinking slow, blinking fast)
• Make the button switch between states
• Agent:
• Grab the Wunderground API code
• github.com/electricimp/reference/tree/master/webservices/wunderground
• Grab weather every 5 mins and change the brightness of the LED based on
the temperature
• Bonus: Create an Umbrella reminder to keep by your front door:
• Every morning the agent checks the weather
• If there’s > 50% chance of rain, LED turns on
• Grab the Twitter API
• github.com/electricimp/reference/tree/master/webservices/twitter
• Make your imp tweet whenever the button is pressed
• Bonus: Control the state of the LED based on a Twitter stream
• Turn the light on whenever something is tweeted with a tracked tag
• Click the button to clear the light

31. Electric Imp Resource
Getting Started Guide electricimp.com/docs/getting-started
API Documentation electricimp.com/docs/api
Squirrel Documentation electricimp.com/docs/squirrel
Reference Code github.com/electricimp/reference
Community Blog community.electricimp.com
Forums forums.electricimp.com