Presentation from FullStack 2017 in London, on JerryScript and JavaScript for IoT devices.

1. JavaScript
FullStack
14 July 2017
all the things

2. Developer Evangelist
Internet of Things

7. https://sloanreview.mit.edu/case-study/ge-big-bet-on-data-and-analytics/

8. ASM

9. PIR Motion sensor
Magic (aka code)
Interwebs
Motion detected
Pls call police

10. 1 var events = 0;
2
3 sensor.onmotiondetected = function() {
4 if (++events > 5) {
5 // intruder!
6 my_awesome_api.post("/call/police", 1);
7 }
8 };

11. <3 JS over C++
• Way faster to develop, debugging and testing are easier
• Harder to break (no off-by-one errors, pointers, seg faults,
memory management)
• Portable to other platforms
• Event system is a natural fit
• Functional language is more expressive

12. Downsides
Running a VM has additional cost
Abstraction may leak
Embedded developers will yell at you

15. Application processor Microcontroller
Raspberry Pi 3 C.H.I.P. micro:bitNUCLEO-F401RE
Full operating system
Hundreds of MB of RAM
Relatively expensive and bulky
Processor, RAM, Storage
Kilobytes of RAM and flash
Slow and needs bare-metal

16. One year on AA battery 0.137 mA
220 mARaspberry Pi 3 (idle)
0.020 mAMicrocontroller w/ BLE
Eddystone, 1s interval, lowest power mode

17. JerryScript Espruino

18. JerryScript
• JavaScript VM
• Originally developed by Samsung
• Managed by JavaScript Foundation
• University of Szeged, Intel, ARM, Samsung, and more
• Runs in 64K of RAM; 200K of ROM
• But... like V8, it's just a VM. Need bindings!

19. Architecture - JS on a microcontroller
JS Application
JS <> C++ bindings
JavaScriptVM
Operating System
(RTOS and drivers)
Startup, peripherals, etc.
JerryScript ARM mbed OS 5
mbed.js

20. 1. Get a dev board (*)
2. $ git clone http://github.com/janjongboom/mbed-js-repl-example
3. $ gulp --target=YOUR_BOARD_NAME
4. Drag .bin file to your board
Getting started
* https://developer.mbed.org/platforms/

22. Digital, analog,
I2C, SPI
Talking to sensors

23. New drivers
Written in C++
Exposed through JS API
http://github.com/janjongboom/mbed-js-wrapper-generator

24. Architecture - JS on a microcontroller
JS Application
JS <> C++ bindings
JavaScriptVM
Operating System
(RTOS and drivers)
Startup, peripherals, etc.
JerryScript ARM mbed OS 5
mbed.js

25. Architecture - JS on a microcontroller
JS Application
JS <> C++ bindings
JavaScriptVM
Operating System
(RTOS and drivers)
Startup, peripherals, etc.
JerryScript ARM mbed OS 5
mbed.js
Your drivers
Using APIs
from mbed.js

26. Demo time!

27. Future...
Code sharing between ecosystems
Adopt a generic module system (like NAPI)
Create standard JS APIs for I2C, SPI, etc.
JerryScript is open source, so come and help!

28. And to us, C++ was the ultimate in Roman
decadence. I mean, it was equivalent to going
and vomiting so you could eat more.
- Steve Yegge
http://steve-yegge.blogspot.co.uk/2008/05/

29. Thank you!
@janjongboom

30. Links
• https://developer.mbed.org/javascript-on-mbed/
• https://github.com/jerryscript-project/jerryscript
• https://github.com/ARMmbed/mbed-js-example
• https://github.com/ARMmbed/mbed-js-ble-example
• https://github.com/janjongboom/mbed-js-repl-example
• https://github.com/janjongboom/mbed-js-wrapper-generator