A Flipper Zero application that repurposes the 125kHz RFID antenna to act as a makeshift metal detector.

• Visual & Audio Feedback: Screen bar graph, increasing pitch, vibration, and LED alerts when metal is near.
• Adjustable Sensitivity: Tune out environmental noise or adjust for specific uses (like scanning a human) with the Left/Right buttons.
• Multiple Modes: Toggle Sound/Vibro modes with the OK button.

• Left / Right: Adjust sensitivity (decrease / increase).
• OK: Cycle through alert modes (Sound+Vibro, Sound only, Vibro only, None).
• Up / Down: Open and close the Help screen.
• Back: Exit the application.

Instead of reading RFID tags, the app repurposes the 125kHz antenna to act as a raw induction coil. By keeping the electromagnetic field active, the app continuously measures the duration (pulse width) of the signal's positive half-waves using timer captures. When metal enters the field, it creates eddy currents that draw energy from the coil, causing the antenna's voltage/amplitude to drop. This drop alters the comparator's output, shortening the measured pulse width or causing it to drop out entirely. The code calculates the delta between a fixed baseline and a moving average of these real-time timing values to trigger the detection UI.

Because this app uses the RFID hardware for an unintended purpose, its range and accuracy are limited. Expect a detection range of only a few cm at most. This tool is primarily educational and experimental, and it is not a replacement for a dedicated metal detector.

The easiest way to install is to download the pre-compiled .fap file from the Releases page and drop it directly onto your Flipper's SD card in the apps/Tools/ folder.

1. Clone this repository into your Flipper firmware (applications_user/rfid_metal_detector) or an empty directory for ufbt.
2. Compile with ufbt or ./fbt fap_rfid_metal_detector.
3. Transfer the compiled .fap to your Flipper's apps/Tools/ folder.

Created by AI (with Tommy's assistance). Licensed under the MIT License.