Teensy 4.1 Intercom – MQTT Button Panel

Demo Video

Turns a Teensy 4.1 + Ethernet kit into a 12-button MQTT panel with Home Assistant discovery.
Each button is exposed as a binary sensor in Home Assistant, with \ON/\OFF\ state, plus an availability topic.

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✨ Features

• 12 inputs (using \INPUT_PULLUP, press = LOW)
• Native Ethernet with QNEthernet
• MQTT via PubSubClient
• Home Assistant auto-discovery
• Availability + periodic re-announce
• 3D printed bracket for mounting

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🖼️ System Overview

This diagram shows how the Teensy fits into the network:
buttons → Teensy 4.1 → Ethernet → MQTT broker → Home Assistant.

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🔌 Wiring Diagram

Each button is wired from a Teensy pin to GND. Pins used are:

\
BTN1..BTN12 → 1, 3, 5, 7, 9, 10, 12, 24, 26, 28, 30, 32 \\

All pins use \INPUT_PULLUP, so pressing pulls the pin LOW.
Other side of every button = GND (shared).

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📸 Hardware Photos

Printing Brackets	Empty Enclosure	Wiring	Final Mount

More photos in hardware/photos.
If your exact filenames differ, update the links above (they were sanitized to remove spaces/parentheses).

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🎥 3D Print Timelapse

▶ 3D print timelapse video

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🛠️ 3D Printed Parts

• [\Teensy_4.1_Ethernet_Mount.stl](hardware/Teensy_4.1_Ethernet_Mount.stl)
  Bracket to hold the Teensy with the PJRC Ethernet kit.

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📡 MQTT

See docs/mqtt-topics.md.

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🏠 Home Assistant Integration

Entities appear automatically under MQTT → Binary Sensors (discovery).

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⚙️ Build Instructions (Arduino IDE 2.3.6)

1. Boards Manager: install “Teensy by PJRC” → select Teensy 4.1
2. Library Manager: install
   • QNEthernet (Shawn Silverman)
   • PubSubClient (Nick O’Leary)
3. Copy \firmware/TeensyIntercom/secrets_example.h\ → \secrets.h\ and edit with your broker details.
   (\secrets.h\ is ignored by Git — safe to commit the project without it.)
4. Open \firmware/TeensyIntercom/TeensyIntercom.ino\
5. Verify → Upload

After upload, check MQTT: \
intercom/availability = online intercom/button/N = ON/OFF \\

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📜 License

MIT — see LICENSE.

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🙏 Credits

• QNEthernet by Shawn Silverman
• PubSubClient by Nick O’Leary
• Built with Arduino IDE 2.3.6

Bill of Materials

See hardware/BOM.md for the full parts list.