Firmware Logic: Timer, Alert, and Reset

The firmware runs on Zephyr RTOS. Here’s the state machine:

1. Idle state — door closed, screen shows product catalog. No timer running.

2. Door open — BLE sends a "door open" event to the hub. A 20-second countdown starts on the display. The user can grab one item.

3. Product removed — the IR beam is broken. The system logs which shelf position was accessed. If the user closes the door within 20 seconds, the transaction is recorded as "pending payment" (handled by the office billing system).

4. Timer expires — if the door remains open past 20 seconds, the buzzer sounds a 3-second pulse, the LED strip flashes red, and a push notification goes to the office manager’s phone via MQTT.

5. Anti-theft alert — if the door is closed but the IR beam shows a product was removed without a corresponding payment event (e.g., someone tried to block the sensor), the system triggers a persistent alert. It only clears when a manager taps an NFC tag on the machine.

The timer is adjustable in firmware — we set 20 seconds as default because that’s enough for one snack grab but too short for someone to try stuffing a bag.

Build Your Own or Let Us Handle It

If you’re designing an office vending machine or any interactive retail display that needs a timer and anti-theft system, the architecture is straightforward. Use a BLE-capable MCU, a reed switch, an IR sensor, and a simple state machine. We’re happy to share the KiCad files or Zephyr code snippets — just ask.

Otherwise, we can design the whole thing for you, from schematic to prototype shipping. Our team handles firmware, PCB layout, 3D enclosure design, and final assembly. We’ve done it for vending, kiosks, and point-of-sale displays across the US, UK, and India.

Ready to build a smart vending machine for your office? Drop us a line. We’ll send you a quote and a timeline within 48 hours.