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Solana DePin Hello World

In this example you will learn how to control a LED using Solana Pay Transaction Requests.

Sequenz.01.mp4

NOTE: If you use a raspberry 5 instead of 4 you need to use different GPIO pin addressed: You can find the addresses like this:

cat /sys/kernel/debug/gpio

Here is the most important ones:

So if it sais 18 in the tutorial you use 589 instead and so on:

gpio-573 (GPIO2               )
 gpio-574 (GPIO3               )
 gpio-575 (GPIO4               )
 gpio-576 (GPIO5               )
 gpio-577 (GPIO6               )
 gpio-578 (GPIO7               )
 gpio-579 (GPIO8               )
 gpio-580 (GPIO9               )
 gpio-581 (GPIO10              )
 gpio-582 (GPIO11              )
 gpio-583 (GPIO12              )
 gpio-584 (GPIO13              )
 gpio-585 (GPIO14              )
 gpio-586 (GPIO15              )
 gpio-587 (GPIO16              )
 gpio-588 (GPIO17              )
 gpio-589 (GPIO18              )
 gpio-590 (GPIO19              )
 gpio-591 (GPIO20              )
 gpio-592 (GPIO21              )
 gpio-593 (GPIO22              )
 gpio-594 (GPIO23              )
 gpio-595 (GPIO24              )
 gpio-596 (GPIO25              )
 gpio-597 (GPIO26              )
 gpio-598 (GPIO27              )

Hardware Required

A Raspberry Pi 4B with WiFi connection, a LED and a 220 ohm resistor. A 32 Gb mini sd card for the raspberry OS.

For example:

https://www.amazon.de/dp/B0C7KXMP7W

https://www.amazon.de/dp/B07WYX8M76

Or if you need a case, sd card and power cable: https://www.amazon.de/RasTech-Raspberry-Active-Cooler-Readers/dp/B0D2WYFS23?th=1

For american builders i would recommend: https://www.amazon.com/RasTech-Raspberry-Active-Cooler-Readers/dp/B0D2WYFS23 and https://www.amazon.com/SunFounder-Raspberry-Compatible-Electronics-Programming/dp/B07WV2HYC6

There may be cheaper and better options. This is an example, any Raspberry 4b and any starter kit with a LED and a resistor will do. Probably a raspberry nano/pico or similar would also work.

Setup Raspberry

Insert the SD card into your computer.

Install the Raspberry OS from here: https://www.raspberrypi.com/software/

Make sure to add the correct wifi information and the user and password and enable SSH. Otherwise you will need a monitor to connect to it later.

Write the os onto the sd card with the Raspberry Pi imager and then put the sd card into the raspberry pi and connect it to a power source.

Bildschirmfoto 2023-08-14 um 15 10 09

optional switch wifi access via ethernet cable

If you did not setup the wifi password in the setup you can also connect the raspberry pi via lan cable to your router and then ssh into it. This is also helpful if you want to connect to it from a different network if you move somewhere else.

  • Connect your computer via lan cable to the raspberry pi (Probably need a connector from usb-c to lan)
  • ssh [email protected]
  • sudo raspi-config and change under system -> wifi to the new wifi network by adding the SSID and the password

Quick blinking test

Connect pin 18 to one side of the LED with a 220 Ohm resistor and pin 16 to the other side like so: Bildschirmfoto 2023-08-14 um 15 10 09 Bildschirmfoto 2023-08-14 um 15 10 09

open terminal

ping raspberrypi.local -> Copy ip address
ssh yourUserName@TheCopiedIpAddress (ssh [email protected])

cd Documents 
nano LED.py

Copy this in the File:

import RPi.GPIO as GPIO
import time
GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
GPIO.setup(18,GPIO.OUT)
print ("LED on")
GPIO.output(18,GPIO.HIGH)
time.sleep(3)
print ("LED off")
GPIO.output(18,GPIO.LOW)

use ctrl +x to exit and y to save

sudo python LED.py

If everything is set up correctly the LED should blink for 3 seconds.

Install Node on the Raspberry Pi:

We want to use js so we can easily use the Solana web3 library.

  1. Type the command:
sudo apt update
  1. Then, install Node.js with the command:
sudo apt install nodejs
  1. Confirm that the installation was successful by checking the available version:
nodejs -v
  1. Install the Node.js package manager (npm):
sudo apt install npm
  1. Verify the installed version:
npm -v

Install nvm: (https://github.com/nvm-sh/nvm)

curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.4/install.sh | bash
export NVM_DIR="$([ -z "${XDG_CONFIG_HOME-}" ] && printf %s "${HOME}/.nvm" || printf %s "${XDG_CONFIG_HOME}/nvm")"
[ -s "$NVM_DIR/nvm.sh" ] && \. "$NVM_DIR/nvm.sh" # This loads nvm
nvm install v18.19.0
nvm use v18.19.0
node --version

Blink script in Node.js

mkdir led
cd led
npm install onoff
nano blink.js

Paste the following code in the file:

var Gpio = require('onoff').Gpio; //include onoff to interact with the GPIO
var LED = new Gpio(18, 'out'); //use GPIO pin 18, and specify that it is output
var blinkInterval = setInterval(blinkLED, 250); //run the blinkLED function every 250ms

function blinkLED() { //function to start blinking
  if (LED.readSync() === 0) { //check the pin state, if the state is 0 (or off)
    LED.writeSync(1); //set pin state to 1 (turn LED on)
  } else {
    LED.writeSync(0); //set pin state to 0 (turn LED off)
  }
}

function endBlink() { //function to stop blinking
  clearInterval(blinkInterval); // Stop blink intervals
  LED.writeSync(0); // Turn LED off
  LED.unexport(); // Unexport GPIO to free resources
}
setTimeout(endBlink, 5000); //stop blinking after 5 seconds

run it with:

sudo node blink.js

The program

The program is a small anchor program which has a boolean which indicated if the LED should be on or off. Not that the program is not yet connected to the LED. We will do that later. Also the seed for the LED account is just a string, so everyone can call this function and switch it on or off. You could add a public key or any other string here to have only certain wallets able to switch the LED on or off.

use anchor_lang::prelude::*;

declare_id!("F7F5ZTEMU6d5Ac8CQEJKBGWXLbte1jK2Kodyu3tNtvaj");

#[program]
pub mod led_switch {
    use super::*;

    pub fn initialize(ctx: Context<Initialize>) -> Result<()> {
        ctx.accounts.led_switch.is_on = false;
        Ok(())
    }

    pub fn switch(ctx: Context<Switch>, is_on: bool) -> Result<()> {
        ctx.accounts.led_switch.is_on = is_on;
        Ok(())
    }
}

#[derive(Accounts)]
pub struct Initialize<'info> {
    #[account(init, payer = authority, space = 8 + 8, seeds = [b"led-switch"], bump)]
    pub led_switch: Account<'info, LedSwitch>,
    #[account(mut)]
    pub authority: Signer<'info>,
    pub system_program: Program<'info, System>,
    pub rent: Sysvar<'info, Rent>,
}

#[derive(Accounts)]
pub struct Switch<'info> {
    #[account(mut, seeds = [b"led-switch"], bump)]
    pub led_switch: Account<'info, LedSwitch>,
    #[account(mut)]
    pub authority: Signer<'info>,
}

#[account]
pub struct LedSwitch {
    pub is_on: bool,
}

Now we want to listen to the account via websocket and trigger the LED

The best way to code on the raspberry pi directly is to use the VS code SSH extension from Microsoft. Install it and click the little blue icon on the bottom left of VSCode to connect. Use the same command you would use in the terminal ssh [email protected] and it will ask you for a password on the top. Then open the folder and start coding.

You can also use scp or rsync to copy the files from the raspberry folder to the raspberry pi. (If you have problems coping files like I had you can also use VNC Viewer to copy the files.) Notice that you need to copy the anchor types from the target folder to the raspberry folder whenever you do changes. (I didn't manage to get it to work without copying the types file over next to the led.ts file.)

Copy all the files from the raspberry folder in this repo on to the raspberry pi. When you deploy your own program donr forget to replace the anchor types as well as your program id.

Then maybe you need to install node types and type script.

npm install -D typescript
npm install -D ts-node

Then you can run

npm i 
and then run the script led.ts 
npx ts-node led.ts

Don't run it with sudo. That gave me problems. You may need to change the rights of the directory to be able to write to it:

chmod -R 777 /directory

Now the LED will already have the correct state that is in the LED account. Next we gonna change it via Solana Pay Transaction requests.

import * as anchor from "@coral-xyz/anchor";
import { Program } from "@coral-xyz/anchor";
import { IDL, LedSwitch } from "../target/types/led_switch";
import { clusterApiUrl, Connection, Keypair, PublicKey } from "@solana/web3.js";
import NodeWallet from "@coral-xyz/anchor/dist/cjs/nodewallet";

var Gpio = require('onoff').Gpio; //include onoff to interact with the GPIO
var LED = new Gpio(18, 'out'); //use GPIO pin 18, and specify that it is output

let connection = new Connection(clusterApiUrl("devnet"));
let wallet = new NodeWallet(new Keypair());
const provider = new anchor.AnchorProvider(connection, wallet, {
  commitment: "processed",
});
anchor.setProvider(provider);

const program = new Program<LedSwitch>(IDL, "F7F5ZTEMU6d5Ac8CQEJKBGWXLbte1jK2Kodyu3tNtvaj", { connection })

console.log("Program ID", program.programId.toString());

startListeningToLedSwitchAccount();

async function startListeningToLedSwitchAccount() {
    const ledSwitchPDA = await anchor.web3.PublicKey.findProgramAddressSync(
        [
          Buffer.from("led-switch"),
        ],
        program.programId,
      )[0];

    const ledSwitchAccount = await program.account.ledSwitch.fetch(
        ledSwitchPDA
    )

    console.log(JSON.stringify(ledSwitchAccount));
    console.log("Led is: ", ledSwitchAccount.isOn);
    if (ledSwitchAccount.isOn) {
      LED.writeSync(1);
    } else {
      LED.writeSync(0);
    }
    
    connection.onAccountChange(ledSwitchPDA, (account) => {
        const decoded = program.coder.accounts.decode(
            "ledSwitch",
            account.data
          )

          if (decoded.isOn) {
            LED.writeSync(1);
          } else {
            LED.writeSync(0);
          }
        console.log("Account changed. Led is: ", decoded.isOn);
    }, "processed")
};

Now the LED will always show the state of the LED account. Next we gonna change the state of the LED account via Solana Pay Transaction requests.

Create a Solana Pay Transaction Request

Solana Pay is not only for payments, but can request any transaction to be signed. The transaction can be signed by any wallet that supports Solana Pay. It consists of two parts. The api which can be found in led-switch/app/pages/api/transaction.ts and the creation of the QR code which can be found in led-switch/app/app/page.tsx and the QrCode in led-switch/app/app/components/qr-code.tsx.

Basically what is happening is that the wallet sends a get request to our API to get a name and icon and then the transaction is created in the nextJS api and send to the wallet. The wallet then signs it. When the transaction is confirmed the LED account is updated and since on the raspberry pi we have a websocket connection to that account the LED turns on or off.

Here is the example API already deployed to vercel for you to try out: https://solana-depin-examples-led.vercel.app/

To run the solana pay transaction request app use:

cd app
yarn install
yarn dev

open http://localhost:3000 in your browser. Notice that the QR code is not working yet. We need to be able to access is from the distance. For that we use ngrok to create a tunnel to our local server. Make an account and install ngrok https://ngrok.com/ open a terminal and type: ngrok http 3000
Then copy the url from the terminal and open it in the browser. Now the QR code should work and switch the LED on and off.

Now you can also copy and print the QR codes and glue them somewhere next to the LED for example.

Deploy

Since you don't want to run ngrok every time it makes sense to deploy the app. Either on the raspberry itself or on for example vercel.com.

Where to go from here

Now you just need imagination to think of what you can do with this. For example you could create a game where you have to scan the QR code to switch the LED on and off or control switches and ramps for marbles. Or you could use a lock to open a door. Or even only open it when there is certain NFT in that wallet. Or you could use it to water plants or feed a hamster during a live stream. Or attach it to a car which can be controlled by the audience.

Have fun and let me know what you build with it!

Optional step: auto start the script on boot (WIP)

Here are three ways on how to start the script on boot: https://www.makeuseof.com/how-to-run-a-raspberry-pi-program-script-at-startup/

I went for step 2 the cron job since it didn't want to risk there being problems during the startup.

First I created a start.sh file:

nano /home/jonas/Documents/led-switch/led-switch/raspberry/start.sh

add

npx ts-node /home/jonas/Documents/led-switch/led-switch/raspberry/led.ts

then run

chmod +x /home/jonas/Documents/led-switch/led-switch/raspberry/start.sh

Then I added this line to the cron config:

crontab -e
@reboot sleep 10 && /home/jonas/Documents/led-switch/led-switch/raspberry/start.sh &

To enable cron logs

sudo nano /etc/rsyslog.conf

and uncomment the line

# cron.*                          /var/log/cron.log

Then restart the service

sudo service rsyslog restart

Now you can check the logs with

sudo cat /var/log/cron.log

Now reboot the raspberry and check if the LED is turning on. (Make sure the program state is set to true ;) )

sudo reboot

If you get error saying that the package crypto is not available it's probably because your sude node version is too low. You can check the node version with

sudo node -v

Update it as described above just using sudo command.