---
title: Simulating with Wokwi
lang: en
type: tuto
phases:
  - preuve-de-concept
tags:
  - eee
  - tuto
  - micropython
prerequis:
  - micropython-en
aa: [RA-PROJET-C03-3/PROJ/5]
draft: false
source_fr: embarque/mcu/micropython/micropython-simulation.md
source_sha256: 8e2b55d4084aa8f90d0bafcdbda2e68592505861ff948362213e6fc7f2060379
---

**Wokwi** is a circuit simulator, free to use in the browser (`wokwi.com`), that can simulate the **Raspberry Pi Pico running MicroPython**: you wire a circuit, write the `main.py`, and watch it run **with no physical hardware**. It is the ideal on-ramp before a board arrives, and a risk-free sandbox for checking wiring before putting a real component in danger. (Unlike [[tinkercad-en|Tinkercad]], which is Arduino-centred, Wokwi covers the Pico and MicroPython: it is the right tool for this module.)

## What is it for?

Wokwi solves three problems that come up constantly in student projects:

- **Starting without hardware** — while the board is still on order, you can write and test your MicroPython code anyway;
- **Testing risky wiring before assembling it** — a badly connected motor, H-bridge or supply can destroy a component, where a simulation costs nothing;
- **Sharing easily** — a Wokwi project is shared as a URL, which is handy for showing a circuit to a supervisor or asking for help remotely.

The tool has limits: not every component is simulated, timing is not realistic down to the microsecond, and some modules are missing. **Wokwi does not replace the real circuit: it speeds up the design loop and makes the first power-up safer.**

## Step by step

Four steps: create a Pico/MicroPython project, place the components, write the code, simulate.

### 1. Create a Pico project in MicroPython

On `wokwi.com`, create a free account, then a **new project**, choosing **Raspberry Pi Pico** and the **MicroPython** language. The editor opens with an empty `main.py` and a Pico already placed on the canvas.

Take a screenshot of *the Wokwi project creation page, with "Raspberry Pi Pico" and the "MicroPython" language selected*.

### 2. Place and wire the components

The **+** button adds components (LED, pushbutton, resistor, sensors, SSD1306 screen and more). You wire them by **clicking from one pin to another**. The wiring is mirrored in a `diagram.json` file that can also be edited by hand.

![Wokwi component picker, Basic category, listing LED, Pushbutton, Pushbutton 6mm and Resistor.|440](/ressources/img/wokwi/ajouter-composant-blink.png)

### 3. Write the `main.py`

In the code editor, write your MicroPython program exactly as you would on a real board (the same `machine` and `time` modules). It is the same code that will run on the physical Pico.

### 4. Run the simulation and watch

Click **▶ (Play)**. Wokwi loads the simulated MicroPython firmware and runs the `main.py`. LEDs light up, displays display. A **serial console** (bottom panel) shows the `print()` output and gives access to the REPL, just as on hardware. The **■ (Stop)** button halts it. You edit on the fly, then run it again.

## Example — a simulated button and LED

Blink, but triggered by a button, so as to show a digital input alongside an output.

**Wiring**: LED on **GP15** through a 220 Ω resistor to GND. Button between **GP14** and GND, in `PULL_UP` (the internal pull-up is enough, no external resistor).

```python
from machine import Pin

bouton = Pin(14, Pin.IN, Pin.PULL_UP)   # pull-up: 0 = pressed
led = Pin(15, Pin.OUT)

while True:
    if bouton.value() == 0:    # button pressed
        led.on()
    else:
        led.off()
```

Run the simulation and click the button: the LED lights up as long as it is held. If the wiring is wrong (button to 3.3 V instead of GND), the behaviour changes: the simulation reproduces the mistake faithfully **without breaking anything**.

Take a screenshot of *the Wokwi simulation of the button and LED circuit, with the button being pressed and the LED lit*.

## Pitfalls

**"It works in Wokwi" ≠ "it works for real".** Simulation idealises: no noise, no contact bounce, no realistic voltage drops, approximate timing. A [[micropython-entree-tor-en|software debounce]] can look pointless in simulation and turn out to be indispensable on the real button. **Validating in simulation is a step, not the last one.**

**Missing components.** Many off-the-shelf sensors are not in the Wokwi library. Check availability before building a simulated proof of concept around one.

**Unfaithful timing.** `time.ticks_ms()` and `ticks_us()`, and time-critical code in general, do not behave as they do on hardware. Do not calibrate a frequency measurement or a timed control loop there without checking on the real board.

**Built-in LED: GP25 in simulation.** On the simulated Pico (non-W), the built-in LED is **GP25**. The `Pin("LED")` shortcut of the Pico W boards may not be recognised. In simulation, write `Pin(25, Pin.OUT)`.

**Internet connection required.** Wokwi is 100% online — with no network, there is no simulation.

## Special case — Tinkercad and local simulation

- **Tinkercad** simulates the [[arduino-en|Arduino]] (Uno/Mega) well but **not the Pico or MicroPython**: for this module, Wokwi is the one to use.
- **MicroPython Unix port** — to test *pure logic* (with no simulated hardware), MicroPython also exists as a PC build: useful for validating an algorithm, not a circuit.

## Where it fits in the project

- **Step 1 of the [[preuve-de-concept-en|proof of concept phase]]** — Wokwi is used to prototype wiring and logic before the first lab session: you arrive with a `main.py` that already works, and gain time on the first power-up.
- **Step 2 of the [[preuve-de-concept-en|proof of concept phase]]** — when a module does not work on the bench, simulating the same wiring separates a logic problem from a hardware one.
- **Demonstration and teaching material** — a simulation can be projected and shared as a URL, and illustrates a piece of logic without touching hardware.

Half an hour of simulation before the first power-up markedly reduces the risk of destroying a component through a bad initial connection.

## Going further

- [wokwi.com](https://wokwi.com/) — the tool itself, with Pico and MicroPython examples ready to fork.
- [[micropython-prise-en-main-en|Getting started with MicroPython]] — the equivalent on real hardware.

## See also

- [[micropython-en|MicroPython]] — the module hub
- [[micropython-prise-en-main-en|Getting started with MicroPython]] — on real hardware
- [[wokwi-en|Wokwi]] — the tool tutorial for this simulator (Arduino and ESP32 side)
- [[simulation-electronique-en|Circuit simulation]] — the hub: method, and how to read results
- [[tinkercad-en|Tinkercad]] — the Arduino equivalent (does not cover the Pico)
- [[microcontroleur-en|Microcontroller]] — an overview of the MCU families