MDB AI Bridge

This is an open source development board that runs a complete MDB (Multi-Drop Bus) vending stack on a single PCB, using three ESP32-S3 as the main platform and KiCad for PCB design. Each ESP32-S3 plays one role of a vending machine - the VMC, the VMflow cashless device and a bill/coin reader - so MDB firmware can be developed, tested and demonstrated without a vending machine.

3 x ESP32-S3: VMC simulator, VMflow cashless device (Wi-Fi/BLE with PCB antenna) and bill/coin reader simulator

MDB links between the chips at 3.3V logic (9-bit, 9600 baud), exposed on a 2x8 header for logic analyzers

USB2514B USB hub: one USB-C cable provides power and three USB-Serial/JTAG ports (flash, console and debug)

Shared I2C bus for scripting and side-channel communication between the three roles

BOOT buttons, reset test pads, status LED and an extra button to inject coin/bill events

Hardware-in-the-loop target for CI pipelines and AI agents (MQTT RPC, vmflow-cli)

This project is part of the VMFlow ecosystem, aiming to standardize and simplify the development of modern, connected vending solutions.

GitHub

https://github.com/nodestark/mdb-esp32-cashless

VMflow

https://vmflow.xyz

Code

VMflow firmware (mdb-esp32-cashless/examples)

https://github.com/nodestark/mdb-esp32-cashless/tree/main/examples

Schematic and Layout

KiCad 9 schematic and PCB

https://github.com/nodestark/mdb-esp32-cashless/tree/main/kicad/mdb-ai-bridge-esp32s3

Download Gerbers Download BOM(Bill of materials)

Oct 16,2026

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MDB AI Bridge - complete vending stack on one ESP32-S3 board

Three ESP32-S3 simulate a VMC, a VMflow cashless device and a bill/coin reader over MDB, all on one USB-C.

Published: Oct 16,2026

Standard PCB

Download Gerber file 0

BOM(Bill of materials)

Centroid file

PCBWay Donate 10% cost To Author

Only PCB

PCB+Assembly

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