This document discusses using JavaScript on microcontrollers. It outlines how to set up JerryScript, a JavaScript VM, on an ARM microcontroller with Mbed OS to run JavaScript applications. It also describes how to create C++ drivers and expose them to JavaScript through bindings. The document provides code examples and demos running JavaScript on a microcontroller board to interact with sensors. It envisions further standardizing JavaScript APIs for microcontrollers and improving code sharing across ecosystems.

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