The Four-Level Continuum — One Project from Simulator to Production

Most educational tools have no exit, and most professional EDA has no entrance. The last session of an Arduino class ends with "nice work" and nothing follows. The core structure of ibouPCB is four levels that bridge this gap inside a single project.

Level 0   Simulator                  No hardware, start instantly in the browser
   ↓      ───── same project · same code ─────
Level 1   Breadboard                 Physical wiring diagram generated automatically
   ↓      ───── same project · same code ─────
Level 2   Shield / HAT               First PCB, tens of boards
   ↓      ───── same project · same code ─────
Level 3   Module-on-board production Hundreds to thousands of boards, certification included

Level definitions

	L0 Simulator	L1 Breadboard	L2 Shield / HAT	L3 Production board
Purpose	Learning · logic verification	Confirm it works physically	First board, form factor fixed	Productization
Hardware	None	Dev board + modules	Dev board + custom board	Custom board alone
MCU form	Virtual	Dev board	Dev board (mounted on top)	Module mounted
Quantity	—	1	1–50	100–10,000
Output	Runnable simulation	Wiring diagram, parts list	Gerber, BOM, assembly drawing	Gerber, BOM, CPL, certification checklist
Cost	Free	Free	Payment point	Payment point
Auto-inserted parts	—	—	Pull-ups, series resistors	+ power tree, decoupling, protection devices, test points

Transition rules

Transitions are not one-way. You can go back from L3 to L0, fix the code, and come back up.
Every transition must pass the verification gates. Both the logic and electrical gates must be green before the next level's files open.
L1 is optional. If you have no hardware, you can go straight from L0 to L2.
Even after reaching L3, the project can keep running the L0 simulation. It serves as a regression test.

Why the gap between breadboard and PCB is a cliff

The idea that "it's verified, so I can just move it to a PCB" is what frustrates beginners most. A circuit verified on a dev board and a production PCB circuit are not the same circuit.

What was on the breadboard	What happens on a production PCB
One Arduino Uno board	ATmega328P + 16 MHz crystal + reset circuit + 5 V / 3.3 V regulators + USB-Serial + ICSP header — all of it has to be drawn by hand
A sensor "module"	The module is already a small PCB itself. You have to decide whether to absorb its circuit or mount the module
Jumper wires	Impedance · noise · crosstalk appear for the first time
(Never visible)	Decoupling, ground plane, ESD protection, reverse-polarity protection, test points
(Never visible)	KC / 技適 (Giteki) radio certification, pick-and-place manufacturability, parts sourcing

Closing this gap is the product. The L2 and L3 converters replace the dev board with a module plus support circuitry, fill in the "never visible" items from the table automatically, and then explain why each one was added.

Why L3 is module-on-board

There are three destinations for production, and their difficulty differs completely. A) Shield / HAT — easy, tens to hundreds of units. B) Module on board — ESP32-WROOM · RP2040 · XIAO · Nano mounted like a component; the real standard for production runs of hundreds to thousands. C) Fully integrated bare chip — a standalone MCU with the crystal · power · USB · bootloader all designed by hand.

ibouPCB does A and B only. C is out of scope. A module already contains the crystal, power sequencing, RF matching, antenna, and even the radio certification, so all you have to draw is module + power + connectors + sensor interfaces. Two layers are enough, and it autoroutes.

Restricting to the Shield / HAT form factor fixes the board outline, connector positions, and power pins by specification. Layer count and impedance control are not needed (two layers, low-speed signals in 99 % of cases). That is why you never draw traces.

Payment points

L0 and L1 are free. Payment happens when you download the Gerber at L2 (once per project) and when you run a production conversion at L3 (once per conversion). A conversion that fails verification is never charged. Board fabrication costs are paid directly to the manufacturer.