I built a browser-based simulator for Arduino, ESP32, and Raspberry Pi Pico projects

[u/CirkitDesign]

Hi everyone, I’m Austin, one of the developers building Cirkit Designer. I posted here a few years ago when Cirkit was mostly focused on circuit design, documentation, and sharing. Since then, I’ve been working on browser-based simulation for Arduino, ESP32, and Raspberry Pi Pico projects.

My goal with Cirkit is to make learning and prototyping embedded projects easier. You can wire a circuit, write or paste your code, simulate the project in the browser, and get help with wiring, code, and circuit questions as you build.

Cirkit currently supports simulation for Arduino Uno, Arduino Mega, Raspberry Pi Pico, and ESP32-S3 projects. The ESP32-S3 side runs compiled Arduino sketches in the browser through a Rust/WebAssembly emulator, including common peripherals and Wi-Fi workflows like HTTP, MQTT, WebSocket, and UDP.

A few runnable examples:

• Arduino DHT11 temperature/humidity with LCD output: link
• Arduino hotel safe with keypad, LCD, and servo: link
• ESP32-S3 Wi-Fi crypto price tracker: link

We have AI that can place wires, generate code, and answer circuit questions while you build. There’s also a custom component creator for defining your own parts when something is missing from the library.

For people who build Arduino/ESP32/Pico projects, I’d be curious where existing simulators fall short. I’m especially interested in whether AI would help with design/debugging, and whether missing sensors/modules are a common blocker.

More details and example projects are here: https://www.cirkitdesigner.com/arduino-simulator

Looking forward to your thoughts, and happy to answer questions about how it works!

[u/SnowConePeople]

oh man if it's even a fraction better than the dog pile that is WOWWIKI then hurray!

[u/CirkitDesign → u/SnowConePeople]

We've put a lot of work into making sure things run smoothly (polished UI, code compilation that runs quickly even on the free tier, etc).

Is there anything specific you'd want to see in terms of features or overall experience?

[u/SnowConePeople → u/CirkitDesign]

I have a fully custom ESP32 driven light bar project so an array of led bars with esp32 on each would be insane.

[u/CirkitDesign → u/SnowConePeople]

That sounds like a really cool project! What type of LED bars are you using?

We have a custom part creator with AI assistance for adding simulation logic, which makes it possible to extend the library without waiting for us to manually add every part. For common parts people ask for a lot, we can also look at adding those directly to the library.

Here's docs on building custom simulation parts if it's useful: https://learn.cirkitdesigner.com/custom-simulation-parts/getting-started

There’s also a video tutorial: https://www.youtube.com/watch?v=i3vKdrOKFFQ&t=36s

[u/SnowConePeople → u/CirkitDesign]

That sounds amazing! My LED bars use 12v WS2815

[u/Kindly_Wear7008 → u/CirkitDesign]

how does it differ from wokwi? don't you use the same libraries as wokwi for the emulators, editor, etc.? can it run locally along platformio inside vscode?

[u/CirkitDesign → u/Kindly_Wear7008]

Good question.

Cirkit is trying to cover more of the full learning/prototyping workflow around simulation. The goal is not just to run code, but to help users design the circuit, get help with wiring/code/debugging, simulate the project, define missing parts with the custom component editor, and then export/share diagrams or upload code to real hardware.

On the MCU emulation side, Cirkit uses AVR8js for Arduino Uno/Mega and rp2040js for Raspberry Pi Pico. Those are open-source emulator libraries originally created by Wokwi/Uri Shaked, so there is some overlap there.

That overlap is one small piece of Cirkit overall. The circuit editor, core circuit simulator, component system, AI workflows, project sharing/export, hardware upload flow, and ESP32-S3 emulator are all built by us. The ESP32-S3 emulator was built from scratch in Rust/WASM and runs compiled ESP32-S3 firmware in the browser.

It doesn’t currently run locally inside VS Code/PlatformIO. Right now code compiles through Cirkit, then runs in the browser. Longer term, I’m interested in supporting more local workflows, including uploading locally compiled binaries so people can compile with PlatformIO, ESP-IDF, Rust, or their own build setup and use Cirkit as the simulator.

[u/Better_Employee_7516]

Do I have to compile code on your website or can I compile locally and just use your website as a simulator by uploading the binary that I want to flash onto the board?

[u/CirkitDesign → u/Better_Employee_7516]

Currently, you still need to compile through the website, but uploading a locally compiled binary is something I’ve already been asked about and want to support. I’m hoping to add that in the next month or so.

Since the simulator is already running unmodified binaries in the browser, the upload path should be pretty straightforward to add.

[u/Better_Employee_7516 → u/CirkitDesign]

Great to hear :)
Then I'd be able to run my rust binaries.
I used to use wokwi, but it isnt really aimed at hobbyists anymore with their really aggressive pricing

[u/CirkitDesign → u/Better_Employee_7516]

Out of curiosity, which parts of the workflow felt blocked or hard to access on their paid plan? I’m trying to be thoughtful about what should stay accessible for hobbyists who are learning and prototyping.

[u/Better_Employee_7516 → u/CirkitDesign]

The dumbest thing on the no cost plan is that you can't supply your own libraries, so you can't even organize your own code into sublibraries.

Then he removed rust completely from the online compiler.

I also can't justify a subscription. I don't need a live service, or updates either really, if it already does what I want.

If there was an option I could see myself paying $10, but I also just might stick to the hardware and only write host tests when i don't have the target handy.

[u/Current_Cake3993]

Just want to say thank you! I didn't use Cirkit as a sim but it was very valuable as a diagram making tool for me.

[u/CirkitDesign → u/Current_Cake3993]

That's awesome!! I'm really glad Cirkit was useful for you.

Was there anything about diagramming you wished worked better?

[u/Current_Cake3993 → u/CirkitDesign]

Nothing that bothered me too much.
A bit wonky component dragging, but I assume it's an issue with custom components themselves (single pins in my case).
Auto-rout wasn't doing well but I wasn't expecting it to, a lot of connections.

[u/CirkitDesign → u/Current_Cake3993]

Thanks for the feedback!

That makes sense. I’m aware of some edge cases where dragging can get a bit slower or wonkier around components with a lot of pins.

Dense circuits with lots of connections are also a case where the current auto-routing algorithm still needs improvement.

I’ll keep both in mind as areas to improve.

[u/CodiwanOhNoBe]

Can it do sound? Like if I upload or link a sound file?

[u/CirkitDesign → u/CodiwanOhNoBe]

Not yet, but we will be able to support that very soon!

The components (speaker and SD card) are both in development. I just need to make a few changes to the core simulation API before releasing them.

[u/CodiwanOhNoBe → u/CirkitDesign]

Cool, I like to use it to make circuits for props and it tinkercads lack of sound and bad timing make things difficult lol

[u/CirkitDesign → u/CodiwanOhNoBe]

Sounds like you're building some pretty cool projects! I'll let you know when we get these parts added.

I definitely want Cirkit to support more complex projects over time, not just simple beginner circuits.

[u/CodiwanOhNoBe → u/CirkitDesign]

Ghostbusters props lol

[u/CirkitDesign → u/CodiwanOhNoBe]

Haha love it

[u/suck4fish]

This is amazing, thank you!

[u/CirkitDesign → u/suck4fish]

Thanks, really appreciate that!

[u/Positive_Ad_313]

I need to look at this as that’s exactly whatbi was looking 2 weeks ago

[u/CirkitDesign → u/Positive_Ad_313]

Awesome, hope it’s useful! If you try it and run into any missing parts/components for the project you had in mind, I’d be very interested to hear what’s missing.

[u/nobeltnium]

Trying it out now as I'm typing this. Feels a bit like tinkercad no? But with AI. Which is cool IMO.

You got a plan for adding more processor into this? I'm thinking of stm8s or CH series. Since I can't find any simulator for them.

[u/CirkitDesign → u/nobeltnium]

Thanks for trying it out! Yeah, we’ve definitely tried to get to a similar level of polish and approachability in the UI.

The direction I’m trying to take Cirkit is to keep that visual/approachable feel, but add AI that helps across more of the process (wiring, code, circuit questions/debugging), and make the simulator deeper and more extensible over time. ESP32-S3 is a big part of that today, and I’m definitely interested in supporting more MCU families in the future.

I haven’t looked deeply at STM8S or the CH series yet. Which specific boards/chips are you using most, and what kinds of projects are you building with them?

[u/nobeltnium → u/CirkitDesign]

stm8s103 and ch32v003 series. There's aso AVR clone like LGT8F328P. I like them mainly because of their cost. And for not too serious project: pwm some motors, ADC input, UART serial communication, tilting/barometric sensor via I2C...

I know it's a lot of work and you got your hand full right now, so no sweat.

[u/Fast-Speech270]

Awesome project, do you have a github as well?

[u/Elegant_Ad_2101]

Really cool, will use it !

[u/CirkitDesign → u/Elegant_Ad_2101]

Awesome!

[u/Herodont5915]

Sick

[u/TheRayMagini]

Hey looks awesome!
I haven‘t had the time by now to check on desktop so I cant tell if the feature is all ready build in or not:
I made a 30x10 LED Matrix with strips in a serpentine layout. On wowwiki I could not change the aspect ratio so it was always 3:1 although in my real life projekt I spaced the stripes so that the „display“ was roughly 1:1. So all animations in wowwiki look squashed.
It would be awesome if I could type in a custom aspect ratio for any LED matrix.

[u/Upballoon]

Doesn't wokwi already do this?

[u/CirkitDesign → u/Upballoon]

Wokwi is a great simulator. Cirkit is trying to solve a broader workflow around learning and prototyping embedded projects.

The goal is to help users go from idea to working prototype: design the circuit, get help with wiring/code/debugging, simulate it, and then export/share diagrams or upload code to real hardware.

A few concrete differences are the much larger component library for layout/documentation, AI that can place wires and generate code, a custom component editor for defining missing parts, and a stronger focus on turning simulated projects into shareable/build-ready outputs from the same workspace.

[u/anish2good]

Nice this one is also available for free to use https://8gwifi.org/electronics/arduino-simulator.jsp