Build Instructions

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• 1

  Supplies

  Electronics:

  1. 1× ESP32 Dev Module — any standard 30/38-pin dev board works; this runs the Morse engine, display, and ESP-NOW beacon
  2. 1× SSD1306 OLED, I2C, 0.96", 128×64 — the standard 4-pin I2C version (SDA/SCL), not SPI
  3. 1× momentary tactile push button — the only input on the device
  4. 1× buzzer, passive or active (optional) — passive is preferable since it can tone at a specific frequency rather than just clicking
  5. 9V battery, or USB power for bench testing
  6. Jumper wires, breadboard for initial wiring
  
  

  Enclosure (cardboard prototype):

  • Corrugated cardboard (an old shipping box works)
  • Black and white paper for the panel finish
  • Hot glue gun + glue sticks
  • Craft knife and a pencil for marking cutouts

  The same electronics stack drops into a PVC or 3D-printed shell later with no changes to wiring or firmware.

• 2

  Wiring

  _________________________________________
  |    Component      |	 Pin	| ESP32 |
  |-------------------|-----------|-------|
  |OLED VCC           |	  —	| 3V3   |
  |OLED GND           | 	  —	|GND    |
  |OLED SDA           |	  —	|GPIO 21|
  |OLED SCL           |	  —	|GPIO 22|
  |Button leg 1       |	  —	|GPIO 4 |
  |Button leg 2       |	  —	|GND    |
  |Buzzer + (optional)|	  —	|GPIO 19|
  |Buzzer − (optional)|	  —	|GND    |

  The button relies on the ESP32's internal pull-up resistor, so no external resistor is needed — it just needs to pull the pin to ground when pressed. If using a passive buzzer, polarity generally doesn't matter; active buzzers are sometimes polarized, so check the datasheet if unclear. A quick continuity check with a multimeter before powering on is worth doing to rule out shorts.
• 3

  Flashing the firmware

  1. Install the Arduino IDE (2.x) from arduino.cc.
  2. Add ESP32 board support: File → Preferences → Additional Boards Manager URLs → https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_index.json Then install esp32 (Espressif Systems) via Boards Manager.
  3. Install the U8g2 library (by oliver/olikraus) via Sketch → Include Library → Manage Libraries. This handles all OLED rendering — menu highlighting, the Morse light-guide box, and beacon status.
  4. Near the top of the sketch, set:

  #define BUZZER_IS_PASSIVE true // false = active buzzer

  1. Select your board and port under Tools, then upload.

  On reset, the OLED should show the SIGNAL splash screen. If the display stays blank, double-check SDA/SCL wiring and confirm the I2C address in code (0x3C) matches your module — some 0.96" boards ship on 0x3D instead.
  

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