Prismo – a simple NFC access controller

Demo	PCB

Prismo is an open-source NFC access controller that you can build yourself for ~500 UAH (~10 USD). Tap a card to unlock a door or power on a machine — fully self-hosted, MIT-licensed.

You can use it, for example, to:

• Open a door
• Turn on a machine
• Control whatever you want with an NFC card/key

Features

• 🟢 Tap-to-unlock — present an NFC/RFID card, get instant LED + buzzer feedback and a relay action.
• 🔓 Build it yourself for ~$10 — off-the-shelf ESP32-C3 + PN532, single-layer PCB.
• 🛠️ DIY-friendly PCB — single-layer, etchable at home; a great first soldering project.
• 🏠 Self-hosted + MQTT — integrates with Home Assistant or your own backend. No cloud lock-in.
• ⚡ One-click flashing — flash a pre-built firmware from your browser, no toolchain required.

How we test our solution

Every change Tested on real hardware — every change runs using a physical Prismo device. We have a test stand that allows us to verify every change and make sure everything works as expected. For more info read the ReadMe from blackbox-e2e.

What you need

Item	Notes
ESP32-C3 Super Mini	The brains. ~$3.
PN532 NFC module	Reads the cards (powered from 3.3 V).
Prismo PCB + components	See the Bill of Materials.
A USB-C cable + a Chrome/Edge browser	For flashing over Web Serial.
2.4 GHz WiFi	The ESP32-C3 is 2.4 GHz only.

Quick start

Full build instructions live in hardware/README.md (PCB + assembly) and firmware/README.md (firmware).

1. Build the board — etch/order the single-layer PCB, solder the components, and connect the PN532 and RGB LED.
2. Flash it — open the web flasher in Chrome and click Flash. No toolchain needed.
3. Connect it — the device boots, joins your 2.4 GHz WiFi, and announces itself over MQTT.
4. Add your card — register the card's UID in the web app; tap to unlock.

Why are we making Prismo?

We started Prismo because we could not find a simple, low‑cost project that:

• Uses easy hardware
• Uses simple, free software
• Is friendly for beginners

Before building more features, we wrote down what we want from this project.

General requirements

• You do not need special knowledge to build and use Prismo.
• You do not need any paid software. Everything needed is free.

Hardware requirements

• The PCB is single‑layer, so it can be made with CNC or a simple toner‑transfer / laser–iron method.
• It should be good as a first soldering project.
• All components should be easy to solder.(We still need to define how to measure “easy to solder”.)
• You do not need special tools to solder or assemble the device.
• All parts should be off‑the‑shelf, easy to buy in common electronics shops.
• The total cost of the device should be low.

Software requirements

• It should be easy to connect Prismo to other systems (for example, a home automation system or a custom app).
• Users should be able to move away from Prismo to another solution without problems.
• The project should use a common programming language that:
• Many developers already know
• Is easy to understand
• Works well with AI tools

Project structure

The repository is a monorepo. That means all components of the project live in one place.

• firmware/ – the software that runs on the Prismo device. This folder has its own README.md.
• hardware/ – the hardware design files, such as KiCad schematics and PCB layout. This folder has its own README.md.
• web/ – the web app used to manage devices, register cards, and flash the board with firmware. This app is containerized and can be run locally or on a remote machine.

Project CI

The project uses GitHub Actions for CI. Every change is built, linted, and — for the firmware — tested on real ESP32-C3 hardware running on a Raspberry Pi rig before it lands on main. The CI also builds the firmware *.bin that the web flasher serves.

License

Prismo is released under the MIT License.