Guide to WiFi on PicoRuby/R2P2

14:00, May 4 2024

This is a preview of what’s to come in my RubyKaigi 2024 talk, and also a guide for people who want to try what I will be talking/have talked at RubyKaigi 2024.

Links to relevant repositories are below:

• PicoRuby
  • Official
  • Fork (has the wlan branch)
• R2P2
  • Official
  • Fork (has the wlan branch)

Please note that I am omitting explanations of what PicoRuby and R2P2 are. Please go check the official repository for those.

Building PC version R2P2

You can build R2P2 that runs on PC with MRUBY_CONFIG=r2p2-bin option. This is used to check functionality that doesn’t depend on devices. I used this to test the cryptography implementation.

The following will get you from a full-scratch Ubuntu installation to building the PC version R2P2. Your mileage may vary but you will most likely start after installing the latest Ruby version.

# build latest ruby
sudo apt install git build-essential autoconf patch rustc libssl-dev libyaml-dev libreadline6-dev zlib1g-dev libgmp-dev libncurses5-dev libffi-dev libgdbm6 libgdbm-dev libdb-dev uuid-dev
git clone https://github.com/rbenv/rbenv.git ~/.rbenv
echo 'eval "$(~/.rbenv/bin/rbenv init - bash)"' >> ~/.bashrc
git clone https://github.com/rbenv/ruby-build.git "$(rbenv root)"/plugins/ruby-build
rbenv install -l
rbenv install 3.3.1
rbenv global 3.3.1

# install gcc-arm-none-eabi
sudo apt install gcc-arm-none-eabi

# clone PicoRuby, then build PC version R2P2
git clone --recursive https://github.com/picoruby/picoruby.git
MRUBY_CONFIG=r2p2-bin rake

# run PC version R2P2
build/no-libc-host/bin/r2p2

Building R2P2

Preparing the build environment

• CMake from apt was too old to build R2P2, so I had to build CMake from source.
  • Download archive and untar it
  • ./bootstrap, make, sudo make install
• Clone R2P2, then git submodule init, git submodule update
• Clone pico-sdk, pico-extras, then specify their paths into environment variables PICO_SDK_PATH and PICO_EXTRAS_PATH
  • pico-sdk
  • pico-extras
• Inside pico-sdk, git submodule init and git submodule update
• Inside pico-sdk, git checkout 1.5.1
• Inside pico-extras, git checkout sdk-1.5.1
  • Note that the tag name is a little different
• Inside R2P2 you will be able to rake now

Troubleshooting

• Something around the line of PICO_SDK_FETCH_FROM_GIT and/or PICO_EXTRAS_FETCH_FROM_GIT: Forget it, set PICO_SDK_PATH and PICO_EXTRAS_PATH explicitly. As far as I know the automatic setup won’t automatically set your pico-sdk and pico-extras version to the one that R2P2 requires, so it’s better to just do them manually.
• (PATH) does not contain a CMakeLists.txt file on pico_extras_import.cmake:62: There is build cache from previous builds that is interfereing with the current build. Delete the content of build/ directory.
• #include <bsp/board.h> giving bsp/board.h: No such file or directory: pico-sdk’s submodules aren’t updated.

Connect to R2P2

Load .uf2 file

Connect your Pico W while pressing the BOOTSEL button. This will give you a storage device named RPI-RP2. Drag and drop the .uf2 file that contains the R2P2 executable (either the one downloaded from GitHub releases or the one you’ve built). After the file has been copied, a storage device named R2P2 will come up on your system. This means that you’re ready to connect with the following steps.

On a Linux

• Connect your Pico W to your computer
• gtkterm --port /dev/ttyACM0

On a Mac

• Connect your Pico W to your computer
• After the storage “R2P2” appears on your desktop:
  • screen /dev/tty.usbmodem1234567890121 115200
    • First argument is the console port
    • Second argument is the baud rate. Sometimes works without this but I get more stable results with this

Blink the on-board LED

…because that’s like Hello World in IoT!

The code written in the rest of the article will be run under irb. There is an option to run code by putting app.rb/app.mrb inside the Pico W’s storage but here we’re doing it on irb.

CYW43.init "JP"
pin = CYW43::GPIO.new(CYW43::GPIO::LED_PIN)
pin.write(1)
pin.write(0)

Note that in a Pico without the WiFi chip the LED pin is not under the CYW43439 chip so it runs like:

led = GPIO.new(25, GPIO::OUT)
led.write(1)
led.write(0)

Connect to WiFi

To try this out, you will have to checkout sylph01/R2P2 wlan branch. The submodule points to a commit under sylph01/picoruby’s wlan branch, so after checking out wlan branch, go inside lib/picoruby, set remote to sylph01/picoruby, then check out the wlan branch.

After R2P2 and lib/picoruby points to the wlan branch, build R2P2 with BOARD=pico_w rake. If this is your first time building and cloning Mbed TLS, some Mbed TLS functions might cause an error saying they lack references or something. Retry the same command again, and the build will complete. After the build completes, you will get the .uf2 file under build/ directory, so copy that onto your Pico W.

Here are some stuff you can try out:

# Connect to WiFi
CYW43.init('JP')
CYW43.enable_sta_mode
CYW43.connect_blocking('your_aps_ssid', 'password', CYW43::Auth::WPA2_MIXED_PSK)

# Resolve DNS names
require 'net'
Net::DNS.resolve('google.com')
Net::DNS.resolve('s01.ninja')
Net::DNS.resolve('192.168.11.1')
Net::DNS.resolve('nonexistent-domain.org')

# HTTPS GET
require 'net'
client = Net::HTTPSClient.new('example.com')
r = client.get('/')