Exploring the World of Electronic Engineering with PicoRuby
December 11, 2025
Based on the presentation “Exploring the World of Electronic Engineering with PicoRuby” by Hayao Kimura at Ruby World Conference 2025 .
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When people think of Ruby, they imagine expressive code, elegant APIs, and beautiful web apps—not motors spinning, sensors buzzing, or circuits glowing on a breadboard. But at Ruby World Conference 2025 , Hayao Kimura (freee K.K.) delivered a talk that flipped that assumption upside down.
His session, “Exploring the World of Electronic Engineering with PicoRuby,” showed how Ruby—yes, the same Ruby you use for Rails—can become a powerful tool for physical computing. And the best part? It makes electronics fun, accessible, and shockingly simple.
This article expands on that presentation, adds context, and enhances it with code examples and explanations to help you start your own PicoRuby journey.
Rediscovering Electronics Through Ruby
Kimura began with a relatable story: early curiosity in electronics, formal studies, then a long detour into web development. Microcontrollers felt distant… until PicoRuby brought the joy back.
The message is clear: You don’t need to be an electrical engineer to build hardware. You only need Ruby.
What Is PicoRuby?
PicoRuby is a lightweight Ruby implementation designed for tiny microcontrollers like the RP2040. What once required C, toolchains, and hours of debugging now looks like this:
led = GPIO.new(25, :OUT)
loop do
led.on
sleep 0.5
led.off
sleep 0.5
end
Small, readable, friendly—pure Ruby.
PicoRuby gives you:
- GPIO input and output
- ADC (analog sensors)
- PWM (motors, LEDs, buzzers)
- UART, SPI, I²C
- Interrupts
- Almost no setup friction
You flash a .uf2 file, connect via serial, write Ruby, and start making things blink, spin, measure, or react.
The “Killer App”: Ruby for Custom Keyboards
Many developers first encounter PicoRuby through programmable keyboards. Firmware like prk_firmware makes it possible to define keymaps in Ruby. It’s an instantly rewarding entry point because your keyboard is something you use every day.
And once you realize you can program hardware in Ruby… you want to build more.
Much more.
A Hands-On Example: Building a Ruby-Powered RC Car
One of the most inspiring components of Kimura’s presentation is a fully functional remote-controlled car built with:
- An RP2040 board running PicoRuby
- A motor driver
- Two DC motors
- A joystick module
- A handful of wires and a breadboard
It’s not just proof-of-concept—it’s simple enough for beginners and powerful enough to understand real-world hardware.
Reading a Joystick with Ruby
A joystick outputs analog voltages. With PicoRuby, reading those values feels natural:
class JoyStick
def initialize(vertical_pin:, horizontal_pin:)
@adc_vertical = ADC.new(vertical_pin)
@adc_horizontal = ADC.new(horizontal_pin)
end
def vertical
@adc_vertical.read
end
def horizontal
@adc_horizontal.read
end
end
No registers. No bit shifting. No headaches.
read returns a number you can use to control the car’s movement.
Driving Motors with PWM
DC motors need PWM signals. Kimura used a dual PWM setup per motor: one signal for forward, one for reverse.
class Motor
def initialize(positive_pin:, negative_pin:)
@pos = PWM.new(positive_pin, frequency: 100_000, duty: 0)
@neg = PWM.new(negative_pin, frequency: 100_000, duty: 0)
end
def update(duty)
if duty >= 0
@pos.duty(duty)
@neg.duty(0)
else
@pos.duty(0)
@neg.duty(-duty)
end
end
end
Again: elegant, readable, and unmistakably Ruby.
Bringing It All Together
The Car class acts as the orchestrator, converting joystick values into motor speeds.
class Car
NEUTRAL = 2000 # Example offset for joystick center
def initialize
@left = Motor.new(positive_pin: 19, negative_pin: 18)
@right = Motor.new(positive_pin: 17, negative_pin: 16)
@js = JoyStick.new(vertical_pin: 26, horizontal_pin: 27)
end
def start!
loop do
calculate_duty
@left.update(@left_duty)
@right.update(@right_duty)
end
end
private
def calculate_duty
vertical = @js.vertical - NEUTRAL
horizontal = @js.horizontal - NEUTRAL
# Convert analog values into motor speeds
@left_duty = vertical + horizontal
@right_duty = vertical - horizontal
end
end
A complete, working robot—written in Ruby.
This is the magic of PicoRuby.
When Firmware Gets Easy, Creativity Explodes
Kimura showed additional projects born from playing with PicoRuby:
- Custom keyboard mods
- Sensor experiments
- A hand-crafted FM radio
- Beautifully designed enclosures and physical builds
Once firmware feels effortless, makers naturally move to the physical world: 3D printing, woodworking, analog circuits, enclosure design.
PicoRuby becomes an amplifier for creativity.
The Future of PicoRuby
The presentation closed with a roadmap:
- Runtime Gems to reuse Ruby components directly on embedded devices
- Better documentation for newcomers
- A complete book on PicoRuby’s internals and practical use cases
- Continued support for educational programs like mruby Girls Matsue 1st
The message: PicoRuby is growing—and you can be part of that growth.
Why This Matters
Kimura’s talk at Ruby World Conference 2025 revealed something profound:
Ruby is not limited to web apps. It can move motors, read sensors, and bring devices to life.
For developers who have always wanted to explore electronics but felt overwhelmed, PicoRuby is the bridge you’ve been waiting for.
You already know Ruby. Now you can use it to build robots.
Final Thought
If you’ve ever thought “I wish I could build hardware, but it looks difficult,” PicoRuby proves the opposite.
Start with an LED. Then a sensor. Then a keyboard. Then a robot.
Ruby can take you all the way.
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