A Beginner's Complete Guide to Microcontroller Programming with Ruby

HASUMI Hitoshi

2023-09-21

A Beginner's Complete
Guide to Microcontroller
Programming with Ruby
hasumikin
Euruko 2023
Vilnius, Lithuania
21st - 23rd September 2023

Part 1
Preparation
Part 2
Getting Started with Microcontroller
Part 3
Exploring PicoRuby Further
Part 4
PicoRuby Under the Hood

self.inspect
Hitoshi HASUMI
hasumikin (GitHub ,ex-Twitter, Bluesky and Threads)
Creator of PicoRuby and PRK Firmware
Committer of CRuby's IRB and Reline
First prize of Fukuoka Ruby Award
(2020 and 2022 )
A final nominee of Ruby Prize 2021

Setup (minimal)
Raspberry Pi Pico
Or other RP2040-based controller
USB cable
Terminal emulator on laptop
RP2040

Raspberry Pi Pico
Raspberry Pi Pico: Microcontroller board
MCU: RP2040
Cortex-Mzero+ (dual)
264 KB RAM
2 MB flash ROM
It generally runs without an OS (bere metal)
ref) Raspberry Pi: Single-board computer
It generally needs an OS like Raspberry Pi OS or Windows
for Arm

Terminal emulator
Linux -> GTKTerm
Windows -> Tera Term
macOS -> PuTTY (I'm not sure )
Traditional CUI/TUI tools may have CR/LF
trouble
cu
screen
minicom

Let's begin 1/4
Download the latest
`R2P2-*.uf2`
from GitHub
https://github.com/picoruby/R2P2/releases

Let's begin 1/4
BTW, R2P2 stands for
Ruby on Raspberry Pi Pico

Let's begin 2/4
Connect Pi Pico and PC while
pressing the BOOTSEL button
You'll find "RPI-RP2" drive in file manager
https://www.raspberrypi.org/documentation/rp2040/getting-started

Let's begin 3/4
Drag & drop `R2P2-*.uf2` into RPI-RP2 drive

Let's begin 4/4
Open a proper
serial port on
terminal emulator

R2P2 Shell should start [Demo]
Unix-like shell running on Raspberry Pi Pico
You can use some
commands like `cd`,
`ls`, `mkdir`, and `irb`

PicoIRB [Demo]
PicoRuby's IRB is running within the R2P2 shell
on Raspberry Pi Pico
Your Ruby snippet is compiled into mruby VM
code and executed on the fly
It means PicoRuby contains an mruby compiler which can
run on a one-chip microcontroller (will be mentioned later)

Part 2
Getting Started with
Microcontroller

GPIO (General Purpose Input/Output)
Fundamental digital I/O
Variety of uses:
Input: Detects on-off state of switch and button
Output: Makes a voltage
You can even implement a communication protocol by
controlling GPIO in milli/micro sec

GPIO --- Blinking LED [Demo]
irb> led = GPIO.new(25, GPIO::OUT)
irb> 5.times do
irb*
led.write 1
irb*
sleep 1
irb*
led.write 0
irb*
sleep 1
irb* end
GPIO25 internally connects to on-board LED through a resistor

GPIO --- Blinking LED by discrete parts
Parts list:
LED (RED)
Resistor (1kΩ)

GPIO --- Blinking LED by discrete parts
irb> pin = GPIO.new(15, GPIO::OUT)

GPIO --- Blinking LED by discrete parts
GPIO15 ===> 1kΩ ===> LED ===> GND
<----- 1.5V -----><--- 1.8V ---->
<------------ 3.3V ------------->
RP2040's logic level: 3.3V
LED voltage drop: 1.8V
(according to LED's datasheet)
Current: (3.3V - 1.8V) / 1kΩ = 1.5mA
(calculated by Ohm's Law)

Study time: Physics
Ohm's Law
V = I * R ⇔ I = V / R ⇔ R = V / I
Kirchhoff's Circuit Laws
Current law: The algebraic sum of currents in a network of
conductors meeting at a point is zero
Voltage law: The directed sum of the potential differences
(voltages) around any closed loop is zero

ADC (Analog to Digital Converter)
ADC handles values in-between by converting
an analog voltage to a digital value
e.g. RP2040's ADC has 12 bits depth and
accordingly takes a raw value from 0 (0 V) to
4095 (3.3 V)
Typical usage:
Temperature sensor
Joystick

ADC --- Temperature [Demo]
irb>
irb>
irb>
irb>
irb*
irb*
irb*
irb*
require 'adc'
adc = ADC.new(:temperature)
adc.read_raw
while true
voltage = adc.read_voltage
puts 27 - (voltage - 0.706) / 0.001721
sleep 1
end
RP2040 has an in-chip temperature sensor that
connects to an ADC channel

ADC --- Temperature by discrete parts
Parts list:
Resistor
Rref: 10kΩ
Thermistor
10kΩ (at 25℃ = 298.15K)
B const: 3950
T0: 298.15 (kelvin)

$ADC --- Temperature by discrete parts irb> require 'adc' irb> Rref = 10000.0 irb> B = 3950.0 irb> T0 = 298.15 irb> def kelvin_temp(rth) irb* temp_inverse = 1 / B * Math.log(rth / Rref) + (1 / T0) irb* 1 / temp_inverse irb* end irb> rth = (3.3 / adc.read_voltage - 1) * Rref irb> puts "#{kelvin_temp(rth) - 273.15} C" => 28.1234 C$ Part 3
Exploring PicoRuby Further

PicoRuby applications
R2P2
Unix-like shell system written in PicoRuby
You may want to say an Operating System in Ruby
PRK Firmware
Keyboard firmware framework for DIY keyboard
You can write your keymap and keyboard's behavior with
Ruby

R2P2 (again)
IRB
Multiple-line editor
Built-in commands and executables (all written
in Ruby)
You can write your own external command

Executables in R2P2
# date
puts Time.now.to_s
# mkdir
Dir.mkdir(ARGV[0])

Write a Ruby script file [Demo]
$> vim hello.rb
Edit the file and save it.
puts "Hello World!"
Then run it.
$> ./hello.rb

$GPIO and ADC work together [Demo] require 'adc' def calc_temp(volt) 27 - (volt - 0.706) / 0.001721 end adc = ADC.new(:temperature) led = GPIO.new(25, GPIO::OUT) while true temp = calc_temp(adc.read_voltage) puts "temp: #{temp} C" led.write(30 < temp ? 1 : 0) sleep 1 end$ R2P2 [Demo]
`/home/app.rb` automatically runs on start up
# You can stop by Ctrl-C
led = GPIO.new(25, GPIO::OUT)
while true
led.write 1
puts "Hello World!"
sleep 1
led.write 0
sleep 1
end

R2P2 [Demo]
`/home/app.rb` automatically runs on start up
# You can stop by Ctrl-C
led = GPIO.new(25, GPIO::OUT)
while true
led.write 1
puts "Hello World!"
sleep 1
led.write 0
sleep 1
end

Serial communication protocols
SPI: High speed, full duplex. e.g. Acceleration
sensor, Color display, etc.
I2C: Low speed, Addressing network with fewer
wires. e.g. RTC, Temperature sensor and
Charactor display, etc.
UART: Buffered asyncronous communication.
e.g. Terminal emulator, Wireless module like BLE
and LTE/5G, etc.

I2C and UART
Parts list:
PCF8523 RTC module
FTDI USB to TTL Serial
Adapter Cable (3.3V)

I2C and UART
github.com/picoruby/rp2040-peripheral-demo
Example of I2C (RTC)
and UART (USB serial)
Watch the demo video
in README.md
Also an example of
how to build your own app

PRK Firmware - Meishi2
require "consumer_key"
kbd = Keyboard.new
kbd.init_pins(
[ 6, 7 ],
# row0, row1
[ 28, 27 ] # col0, col1
)
kbd.add_layer :default, %i[ RAISE KC_2 KC_A KC_4 ]
kbd.add_layer :raise,
%i[ RAISE
KC_AUDIO_VOL_UP
KC_AUDIO_VOL_DOWN
KC_AUDIO_MUTE ]
kbd.define_mode_key :RAISE, [ :KC_SPACE, :raise, 200, 200 ]
kbd.start!

mruby and PicoRuby
mruby
General purpose embedded Ruby implementation written
by Matz
PicoRuby
Another implementation of murby targeting on one-chip
microcontroller (smaller foot print)
Based on the mruby's VM code standard

$Small foot print $ valgrind --tool=massif --stacks=yes path/to/(mruby|picoruby) -e 'puts "Hello World!"' \ \ \ \ `massif.out.[pid]` file will be created. Then, $ ms_print massif.out.1234 | less$

Small foot print
--------------------------------------------------------------------------------
Command:
mruby -e 'puts "Hello World!"'
Massif arguments:
--stacks=yes
ms_print arguments: massif.out.18391
--------------------------------------------------------------------------------
KB
133.5^
#
|
#
|
#
|
#
|
#
|
#
|
#
|
#
|
@
:@:::@:#:
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@:@@@::::@:::@:#::
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::@::::::@::::::::@:@@@::::@:::@:#::
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@:::::::::@@::::@:::@::::::@:::::: :@:@@@::::@:::@:#::
|
@@@:::@:::::::::@ :: :@:::@::::::@:::::: :@:@@@::::@:::@:#::
|
@ :: @:::::::::@ :: :@:::@::::::@:::::: :@:@@@::::@:::@:#::
|
@ :: @:::::::::@ :: :@:::@::::::@:::::: :@:@@@::::@:::@:#::
|
@ :: @:::::::::@ :: :@:::@::::::@:::::: :@:@@@::::@:::@:#::
|
@ :: @:::::::::@ :: :@:::@::::::@:::::: :@:@@@::::@:::@:#::
|
@ :: @:::::::::@ :: :@:::@::::::@:::::: :@:@@@::::@:::@:#::
|
@ :: @:::::::::@ :: :@:::@::::::@:::::: :@:@@@::::@:::@:#::
| @
@ :: @:::::::::@ :: :@:::@::::::@:::::: :@:@@@::::@:::@:#::
0 +----------------------------------------------------------------------->Mi
0
1.281
# Note: Measured in 64 bit Ubuntu

Small foot print
--------------------------------------------------------------------------------
Command:
picoruby -e 'puts "Hello World!"'
Massif arguments:
--stacks=yes
ms_print arguments: massif.out.21752
--------------------------------------------------------------------------------
KB
9.820^
#
|
@:#:::
|
@:#:::::
|
@:#:::::
|
@:#:::::
|
@
@:#:::::
|
@
@:#:::::
|
@
: @:#:::::
|
@
::: @:#:::::
|
@
: ::: @:#:::::
|
@
::@::::@:#:::::@
|
@
::@::::@:#:::::@
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@:
:::::@::::@:#:::::@
|
@:::
:: :::@::::@:#:::::@
|
@::
::: :::@::::@:#:::::@
|
@:: :
::: :::@::::@:#:::::@
|
@:: :
::: :::@::::@:#:::::@
|
:@:: :
:
:: :@:@: :
:@@: ::@::::: ::: :::@::::@:#:::::@
|
:@:: :::::::::::::::@:@:@:::::@ ::: @:: : :::: :::@::::@:#:::::@
|::::::@::@:: :::
::: :::::@:@:@:: ::@ : : @:: : :::: :::@::::@:#:::::@
0 +----------------------------------------------------------------------->ki
0
324.5
# Note: Measured in 64 bit Ubuntu

Small foot print
RAM consumption of `puts "Hello World!"`
mruby: 133.5 KB (on 64 bit)
PicoRuby: 9.82 KB (on 64 bit)
RP2040 (32 bit) has 264 KB RAM
Only small applications written in mruby should work
R2P2 and PRK Firmware should be written in PicoRuby

PicoRuby ecosystem
Picogems
PRK Firmware is also a Picogem
Peripheral gems
picoruby-gpio
picoruby-adc
picoruby-i2c
picoruby-spi
picoruby-uart
Peripheral interface guide
https://github.com/mruby/microcontroller-peripheral-interface-guide

PicoRuby ecosystem
Build system forked from mruby
You can build your application in a similar way to mruby
You can also write your gem and host it on your GitHub
RP2040 is the only target as of now though,
Carefully designed to keep portability

Restriction of PicoRuby
Minimum built-in classes and methods
Doesn't support
Some syntax like heredoc and numbered parameters
Module due to VM implementation
No strict distinction between instance methods
and singleton methods
Some bugs (because I'm lazy ).
See github.com/picoruby/picoruby/issues

Conclusion
PicoRuby is a Ruby implementaiton targeting on
one-chip microcontroller
You can develop your microcontroller
application step by step using the R2P2 and IRB
You need only R2P2 to run small applications
Future work
BLE and WiFi with Raspberry Pi Pico W (soon)
Porting to microcontrollers other than RP2040 (someday)

RubyKaigi 2024
[ad]
In Okinawa
May 15th - 17th
1000+ attendees, tons of tech talks
and various parties
https://098free.com/photos/14262/

That's all! Visit repos and stargaze
github.com/picoruby/picoruby
github.com/picoruby/R2P2
github.com/picoruby/prk_firmware
github.com/picoruby/rp2040-peripheral-demo

$Small foot print $ valgrind --tool=massif --stacks=yes path/to/(mruby|picoruby) -e 'puts "Hello World!"' \ \ \ \ `massif.out.[pid]` file will be created. Then, $ ms_print massif.out.1234 | less$

Description

Presentation slide for Euruko 2023

Text

Page: 1

A Beginner's Complete
Guide to Microcontroller
Programming with Ruby
hasumikin
Euruko 2023
Vilnius, Lithuania
21st - 23rd September 2023

Page: 2

Part 1
Preparation
Part 2
Getting Started with Microcontroller
Part 3
Exploring PicoRuby Further
Part 4
PicoRuby Under the Hood

Page: 3

self.inspect
Hitoshi HASUMI
hasumikin (GitHub ,ex-Twitter, Bluesky and Threads)
Creator of PicoRuby and PRK Firmware
Committer of CRuby's IRB and Reline
First prize of Fukuoka Ruby Award
(2020 and 2022 )
A final nominee of Ruby Prize 2021

Page: 4

Part 1
Preparation

Page: 5

Setup (minimal)
Raspberry Pi Pico
Or other RP2040-based controller
USB cable
Terminal emulator on laptop
RP2040

Page: 6

Raspberry Pi Pico
Raspberry Pi Pico: Microcontroller board
MCU: RP2040
Cortex-Mzero+ (dual)
264 KB RAM
2 MB flash ROM
It generally runs without an OS (bere metal)
ref) Raspberry Pi: Single-board computer
It generally needs an OS like Raspberry Pi OS or Windows
for Arm

Page: 7

Terminal emulator
Linux -> GTKTerm
Windows -> Tera Term
macOS -> PuTTY (I'm not sure )
Traditional CUI/TUI tools may have CR/LF
trouble
cu
screen
minicom

Page: 8

Let's begin 1/4
Download the latest
`R2P2-*.uf2`
from GitHub
https://github.com/picoruby/R2P2/releases

Page: 9

Let's begin 1/4
BTW, R2P2 stands for
Ruby on Raspberry Pi Pico

Page: 10

Let's begin 2/4
Connect Pi Pico and PC while
pressing the BOOTSEL button
You'll find "RPI-RP2" drive in file manager
https://www.raspberrypi.org/documentation/rp2040/getting-started

Page: 11

Let's begin 3/4
Drag & drop `R2P2-*.uf2` into RPI-RP2 drive

Page: 12

Let's begin 4/4
Open a proper
serial port on
terminal emulator

Page: 13

R2P2 Shell should start [Demo]
Unix-like shell running on Raspberry Pi Pico
You can use some
commands like `cd`,
`ls`, `mkdir`, and `irb`

Page: 14

PicoIRB [Demo]
PicoRuby's IRB is running within the R2P2 shell
on Raspberry Pi Pico
Your Ruby snippet is compiled into mruby VM
code and executed on the fly
It means PicoRuby contains an mruby compiler which can
run on a one-chip microcontroller (will be mentioned later)

Page: 15

Part 2
Getting Started with
Microcontroller

Page: 16

GPIO (General Purpose Input/Output)
Fundamental digital I/O
Variety of uses:
Input: Detects on-off state of switch and button
Output: Makes a voltage
You can even implement a communication protocol by
controlling GPIO in milli/micro sec

Page: 17

GPIO --- Blinking LED [Demo]
irb> led = GPIO.new(25, GPIO::OUT)
irb> 5.times do
irb*
led.write 1
irb*
sleep 1
irb*
led.write 0
irb*
sleep 1
irb* end
GPIO25 internally connects to on-board LED through a resistor

Page: 18

GPIO --- Blinking LED by discrete parts
Parts list:
LED (RED)
Resistor (1kΩ)

Page: 19

GPIO --- Blinking LED by discrete parts
irb> pin = GPIO.new(15, GPIO::OUT)

Page: 20

GPIO --- Blinking LED by discrete parts
GPIO15 ===> 1kΩ ===> LED ===> GND
<----- 1.5V -----><--- 1.8V ---->
<------------ 3.3V ------------->
RP2040's logic level: 3.3V
LED voltage drop: 1.8V
(according to LED's datasheet)
Current: (3.3V - 1.8V) / 1kΩ = 1.5mA
(calculated by Ohm's Law)

Page: 21

Study time: Physics
Ohm's Law
V = I * R ⇔ I = V / R ⇔ R = V / I
Kirchhoff's Circuit Laws
Current law: The algebraic sum of currents in a network of
conductors meeting at a point is zero
Voltage law: The directed sum of the potential differences
(voltages) around any closed loop is zero

Page: 22

ADC (Analog to Digital Converter)
ADC handles values in-between by converting
an analog voltage to a digital value
e.g. RP2040's ADC has 12 bits depth and
accordingly takes a raw value from 0 (0 V) to
4095 (3.3 V)
Typical usage:
Temperature sensor
Joystick

Page: 23

ADC --- Temperature [Demo]
irb>
irb>
irb>
irb>
irb*
irb*
irb*
irb*
require 'adc'
adc = ADC.new(:temperature)
adc.read_raw
while true
voltage = adc.read_voltage
puts 27 - (voltage - 0.706) / 0.001721
sleep 1
end
RP2040 has an in-chip temperature sensor that
connects to an ADC channel

Page: 24

ADC --- Temperature by discrete parts
Parts list:
Resistor
Rref: 10kΩ
Thermistor
10kΩ (at 25℃ = 298.15K)
B const: 3950
T0: 298.15 (kelvin)

Page: 25

ADC --- Temperature by discrete parts
Parts list:
Resistor
Rref: 10kΩ
Thermistor
10kΩ (at 25℃ = 298.15K)
B const: 3950
T0: 298.15 (kelvin)

Page: 26

ADC --- Temperature by discrete parts
irb> require 'adc'
irb> Rref = 10000.0
irb> B = 3950.0
irb> T0 = 298.15
irb> def kelvin_temp(rth)
irb*
temp_inverse = 1 / B * Math.log(rth / Rref) + (1 / T0)
irb*
1 / temp_inverse
irb* end
irb> rth = (3.3 / adc.read_voltage - 1) * Rref
irb> puts "#{kelvin_temp(rth) - 273.15} C"
=> 28.1234 C

Page: 27

Part 3
Exploring PicoRuby Further

Page: 28

PicoRuby applications
R2P2
Unix-like shell system written in PicoRuby
You may want to say an Operating System in Ruby
PRK Firmware
Keyboard firmware framework for DIY keyboard
You can write your keymap and keyboard's behavior with
Ruby

Page: 29

R2P2 (again)
IRB
Multiple-line editor
Built-in commands and executables (all written
in Ruby)
You can write your own external command

Page: 30

Executables in R2P2
# date
puts Time.now.to_s
# mkdir
Dir.mkdir(ARGV[0])

Page: 31

Write a Ruby script file [Demo]
$> vim hello.rb
Edit the file and save it.
puts "Hello World!"
Then run it.
$> ./hello.rb

Page: 32

Or just drag and drop [Demo]

Page: 33

GPIO and ADC work together [Demo]
require 'adc'
def calc_temp(volt)
27 - (volt - 0.706) / 0.001721
end
adc = ADC.new(:temperature)
led = GPIO.new(25, GPIO::OUT)
while true
temp = calc_temp(adc.read_voltage)
puts "temp: #{temp} C"
led.write(30 < temp ? 1 : 0)
sleep 1
end

Page: 34

R2P2 [Demo]
`/home/app.rb` automatically runs on start up
# You can stop by Ctrl-C
led = GPIO.new(25, GPIO::OUT)
while true
led.write 1
puts "Hello World!"
sleep 1
led.write 0
sleep 1
end

Page: 35

Serial communication protocols
SPI: High speed, full duplex. e.g. Acceleration
sensor, Color display, etc.
I2C: Low speed, Addressing network with fewer
wires. e.g. RTC, Temperature sensor and
Charactor display, etc.
UART: Buffered asyncronous communication.
e.g. Terminal emulator, Wireless module like BLE
and LTE/5G, etc.

Page: 36

I2C and UART
Parts list:
PCF8523 RTC module
FTDI USB to TTL Serial
Adapter Cable (3.3V)

Page: 37

I2C and UART
github.com/picoruby/rp2040-peripheral-demo
Example of I2C (RTC)
and UART (USB serial)
Watch the demo video
in README.md
Also an example of
how to build your own app

Page: 38

PRK Firmware - Corne (CRKBD)

Page: 39

PRK Firmware - Meishi2
require "consumer_key"
kbd = Keyboard.new
kbd.init_pins(
[ 6, 7 ],
# row0, row1
[ 28, 27 ] # col0, col1
)
kbd.add_layer :default, %i[ RAISE KC_2 KC_A KC_4 ]
kbd.add_layer :raise,
%i[ RAISE
KC_AUDIO_VOL_UP
KC_AUDIO_VOL_DOWN
KC_AUDIO_MUTE ]
kbd.define_mode_key :RAISE, [ :KC_SPACE, :raise, 200, 200 ]
kbd.start!

Page: 40

Part 4
PicoRuby Under the Hood

Page: 41

mruby and PicoRuby
mruby
General purpose embedded Ruby implementation written
by Matz
PicoRuby
Another implementation of murby targeting on one-chip
microcontroller (smaller foot print)
Based on the mruby's VM code standard

Page: 42

Small foot print
$ valgrind
--tool=massif
--stacks=yes
path/to/(mruby|picoruby)
-e 'puts "Hello World!"'
\
\
\
\
`massif.out.[pid]` file will be created. Then,
$ ms_print massif.out.1234 | less

Page: 43

Small foot print
--------------------------------------------------------------------------------
Command:
mruby -e 'puts "Hello World!"'
Massif arguments:
--stacks=yes
ms_print arguments: massif.out.18391
--------------------------------------------------------------------------------
KB
133.5^
#
|
#
|
#
|
#
|
#
|
#
|
#
|
#
|
@
:@:::@:#:
|
@:@@@::::@:::@:#::
|
::@::::::@::::::::@:@@@::::@:::@:#::
|
@:::::::::@@::::@:::@::::::@:::::: :@:@@@::::@:::@:#::
|
@@@:::@:::::::::@ :: :@:::@::::::@:::::: :@:@@@::::@:::@:#::
|
@ :: @:::::::::@ :: :@:::@::::::@:::::: :@:@@@::::@:::@:#::
|
@ :: @:::::::::@ :: :@:::@::::::@:::::: :@:@@@::::@:::@:#::
|
@ :: @:::::::::@ :: :@:::@::::::@:::::: :@:@@@::::@:::@:#::
|
@ :: @:::::::::@ :: :@:::@::::::@:::::: :@:@@@::::@:::@:#::
|
@ :: @:::::::::@ :: :@:::@::::::@:::::: :@:@@@::::@:::@:#::
|
@ :: @:::::::::@ :: :@:::@::::::@:::::: :@:@@@::::@:::@:#::
| @
@ :: @:::::::::@ :: :@:::@::::::@:::::: :@:@@@::::@:::@:#::
0 +----------------------------------------------------------------------->Mi
0
1.281
# Note: Measured in 64 bit Ubuntu

Page: 44

Small foot print
--------------------------------------------------------------------------------
Command:
picoruby -e 'puts "Hello World!"'
Massif arguments:
--stacks=yes
ms_print arguments: massif.out.21752
--------------------------------------------------------------------------------
KB
9.820^
#
|
@:#:::
|
@:#:::::
|
@:#:::::
|
@:#:::::
|
@
@:#:::::
|
@
@:#:::::
|
@
: @:#:::::
|
@
::: @:#:::::
|
@
: ::: @:#:::::
|
@
::@::::@:#:::::@
|
@
::@::::@:#:::::@
|
@:
:::::@::::@:#:::::@
|
@:::
:: :::@::::@:#:::::@
|
@::
::: :::@::::@:#:::::@
|
@:: :
::: :::@::::@:#:::::@
|
@:: :
::: :::@::::@:#:::::@
|
:@:: :
:
:: :@:@: :
:@@: ::@::::: ::: :::@::::@:#:::::@
|
:@:: :::::::::::::::@:@:@:::::@ ::: @:: : :::: :::@::::@:#:::::@
|::::::@::@:: :::
::: :::::@:@:@:: ::@ : : @:: : :::: :::@::::@:#:::::@
0 +----------------------------------------------------------------------->ki
0
324.5
# Note: Measured in 64 bit Ubuntu

Page: 45

Small foot print
RAM consumption of `puts "Hello World!"`
mruby: 133.5 KB (on 64 bit)
PicoRuby: 9.82 KB (on 64 bit)
RP2040 (32 bit) has 264 KB RAM
Only small applications written in mruby should work
R2P2 and PRK Firmware should be written in PicoRuby

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PicoRuby ecosystem
Picogems
PRK Firmware is also a Picogem
Peripheral gems
picoruby-gpio
picoruby-adc
picoruby-i2c
picoruby-spi
picoruby-uart
Peripheral interface guide
https://github.com/mruby/microcontroller-peripheral-interface-guide

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PicoRuby ecosystem
Build system forked from mruby
You can build your application in a similar way to mruby
You can also write your gem and host it on your GitHub
RP2040 is the only target as of now though,
Carefully designed to keep portability

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Restriction of PicoRuby
Minimum built-in classes and methods
Doesn't support
Some syntax like heredoc and numbered parameters
Module due to VM implementation
No strict distinction between instance methods
and singleton methods
Some bugs (because I'm lazy ).
See github.com/picoruby/picoruby/issues

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Conclusion
PicoRuby is a Ruby implementaiton targeting on
one-chip microcontroller
You can develop your microcontroller
application step by step using the R2P2 and IRB
You need only R2P2 to run small applications
Future work
BLE and WiFi with Raspberry Pi Pico W (soon)
Porting to microcontrollers other than RP2040 (someday)

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RubyKaigi 2024
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In Okinawa
May 15th - 17th
1000+ attendees, tons of tech talks
and various parties
https://098free.com/photos/14262/

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That's all! Visit repos and stargaze
github.com/picoruby/picoruby
github.com/picoruby/R2P2
github.com/picoruby/prk_firmware
github.com/picoruby/rp2040-peripheral-demo