Open the door of embedded systems to IoT (the Internet of things) !

mruby on LEGO Mindstorms EV3 ®

Takehiko YOSHIDA@chihayafuru

Agenda

Self-introduction What's LEGO Mindstorms◦ Standard Programming Environment

◦ Extended Programming Environment (ev3dev)

Can we use mruby in embedded systems?◦ Example of a light sensor for Mindstorms RCX

◦ APIs for EV3s color sensor implemented with mruby

Concluding Remarks Demonstration of the "RUBY JINJA"

Self-introduction

I'm from Matsumoto city, Nagano.

I work in a manufacturer of information-related equipment as a programmer.

Takehiko YOSHIDA@chihayafuru

A hierarchy ofa Japanese manufacturing industry

Samurai

Farmer

Artisan

Trader

Mechanical Engineer

Electrical Engineer

Software Engineer

What's LEGO Mindstorms

Educational Tool ＞ Toy

STEM education◦ Science

◦ Technology

◦ Engineering

◦ Mathematics

History of LEGO Mindstorms

1st gen.Mindstorms RCX

2nd gen.Mindstorms NXT

3rd gen.Mindstorms EV3

Release DATE 1998 2006 2013

CPUH8

16MHzARM7

48 MHzARM9

300 MHz

RAM 32 KB 64 KB 16 MB

Standard Firmware Architecture

OS (Linux)

SystemProgram

Device driver (kernel module)

VM (Virtual Machine)

UserProgram

DirectCommand

Extended Firmware

ev3dev◦ full Debian 7 (wheezy)

Linux Distribution.

◦ customized for the LEGO MINDSTORM

EV3 controller.

◦ Bootable from microSD/SDHC card

Available Programming Language

C / C++

Python

JavaScript (Node.js)

Lua

Go

Ruby

What's mruby ?

mruby is the lightweight implementation of Ruby language complying to (part of) the ISO standard. Its syntax is Ruby 1.9 compatible.

mruby can be linked and embedded into your application.

https://github.com/mruby/mruby

Can we use "mruby"in embedded systems ?

Real-time constraint• Can mruby meet the deadline ?• A process of GC (Garbage Collection)

deactivate other interrupts.

An example of a light sensor for1st gen. Mindstorms RCX

LED Light

Photo Detector

Circuit diagram of general light sensor

Signal

Power

Common

Out

In

LED

Photodiode(Photo Detector)

Connector of Mindstorms RCX

Circuit diagram of the RCX’s light sensor

Signal

Power

Common

Out

In

Waveforms of a signal voltage from the Light Sensor for RCX

Oscilloscope

reflected light is strong reflected light is weak

delay of programmed cycle

Color Sensor API with mruby for Mindstorms EV3

Initializer of Color sensor

Ev3Color.new(port)

port : "in1", "in2", "in3" , "in4"

Connector of Mindstorms EV3

3 modes of Color Sensor

Ev3Color#mode=(mode)

EV3Color.Mode.COL-REFLECTEV3Color.Mode.COL-AMBIENTEV3Color.Mode.RGB-RAW

Evolution of Mindstorms

Intelligent

Brick

Light

Sensor

1st gen.

Mindstorms RCX

2nd gen.

Mindstorms NXT

3rd gen.

Mindstorms EV3

ANALOG

ANALOG

DIGITAL

Concluding Remarks

What is mruby suitable for ?

What is mruby NOT suitable for ?

What is mruby NOT suitable for ?

Reaching a hardware limit under software control.

Be willing to work in the background of mechanics and electronics, and struggle with C/C++, assembly language.

What is mruby suitable for ?

High-functional / Multi-functional electric devices

Newly-developed Cloud servicesCreating new value with mashup technology

References

LEGO Mindstorms®http://www.lego.com/en-us/mindstorms/

ev3devhttp://www.ev3dev.org/

mrubyhttps://github.com/mruby/mruby

mruby-ev3devhttps://github.com/chihayafuru/mruby-ev3dev