flipperzero-letterbeacon

A letter/number/symbol Morse beacon on RFID/NFC interfaces of the Flipper Zero

(banner has been made with Dall.E 2)

Like Russia with their HF letter beacons, it's possible to use the Flipper Zero as a letter/number/symbol Morse beacon. Flipper Zero has multiple RF interfaces (RFID, NFC and UHF) and it's possible to transmit raw data over these interfaces.

This application can transmit the whole alphabet (A to Z), numbers (0 to 9) and symbols in Morse via RFID (125 kHz) and NFC (13.56 MHz) interfaces.

On RFID (125 kHz) range is about 5 meters with a small loop antenna. With an amplified loop, the range can extend to 15 meters according to my measurements.

On NFC (13.56 MHz) range is about 50 meters with a small loop antenna.

Gallery

Menu of the application:

The LED turns red when transmitting via RFID and blue when using NFC

Airspy Discovery HF+ SDR bas been used during these tests with a small loop antenna. Following measures have been made at a distance of 2m from the Flipper Zero.

A letter:

3 number:

NFC at 65m:

RFID at 10m:

Build the program

Assuming the toolchain is already installed, copy flipper_letterbeacon directory to applications_user

Plug your Flipper Zero and build the RFID beacon:

./fbt launch_app APPSRC=applications_user/flipper_letterbeacon

The program will automatically be launched after compilation

Button assignments:

button	function
Left/Right [short press]	Select the letter or the value of tick/pause in ms
Left/Right [long press]	Select the letter or the value of tick/pause in ms (more)
Up/Down [short press]	Navigate in the menu
Ok [short press]	Choose between RFID/NFC
Ok [long press]	Enable/disable the transmission
Back [long press]	Exit

If you don't want to build this application, just simply copy flipper_letterbeacon.fap on your Flipper Zero

Build has been made with official toolchain (1.3.4), API Mismatch error may appear if you are using custom firmware. You can bypass this error but the program may crash.

What's next ?

• Choose the speed morse code DONE !
• Transmit on NFC interface (13.56 MHz), range is wider than RFID DONE !
• Transmit on UHF interface (433 MHz, etc)
• Transmit personalized text message over the air

Changelog

• 2025-05-29

  • Add TX to the NFC interface (13.56 MHz)
  • Pause between transmissions is now accurate
  • '-' is now used to display a dash instead of '_'
  • Project has been renamed from flipperzero-rfidbeacon to flipperzero-letterbeacon

• 2025-05-25

  • Add customizable transmission speed
  • Add adjustable pause timing

• 2023-07-11

  • Bug fixing
  • Symbols have been added
  • Morse code view has been added

• 2023-07-09

  • Initial release