Flo Period Tracker for Flipper Zero

May 27, 2026 · View on GitHub

A menstrual cycle tracking application for Cat on her Flipper, following a standard 14-day luteal phase model.

Author

Harim Woo

Features

  • Status Screen — Shows current cycle day, days until next period, fertile window status, and average cycle length
  • Calendar View — Monthly calendar with period days highlighted (filled blocks). Navigate months with Left/Right
  • Log Period — Record a new period with date and duration using the D-pad
  • Settings — Configure average cycle length (20–45 days) and default period duration (1–14 days)
  • Predictions — Automatic prediction of next period, ovulation, and fertile window based on logged data
  • Persistent Storage — All data is saved to the Flipper's SD card and persists across reboots

How to Build

Prerequisites

  1. Clone the Flipper Zero firmware
  2. Set up the build environment following the official docs

Build Steps

  1. Copy the flipper-flo-tracker folder into the firmware's applications_user/ directory:

    cp -r flipper-flo-tracker /path/to/flipperzero-firmware/applications_user/flo_tracker

  2. Build the app using fbt (Flipper Build Tool):

    cd /path/to/flipperzero-firmware
./fbt fap_flo_tracker

  3. The compiled .fap file will be in build/f7-firmware-D/.extapps/flo_tracker.fap

  4. Copy it to your Flipper's SD card under apps/Tools/ or use:

    ./fbt launch_app APPSRC=applications_user/flo_tracker

Using ufbt (Standalone)

Alternatively, use ufbt for standalone builds without cloning the full firmware:

# Install ufbt
pip install ufbt

# Navigate to the app directory
cd flipper-flo-tracker

# Build
ufbt

# Flash to Flipper (connected via USB)
ufbt launch

Usage

  1. First launch — Go to "Log Period" and enter the start date and duration of your most recent period
  2. Status — The main status screen shows predictions based on your logged data
  3. Calendar — Visual overview of your cycle with period days marked
  4. Settings — Adjust cycle length and period duration defaults (auto-calculated after 2+ logged periods)

File Structure

flo_tracker/
├── application.fam      # Flipper app manifest
├── flo_tracker.c         # Main app entry, menu, settings, lifecycle
├── flo_app.h             # App struct and view model definitions
├── flo_data.h            # Data types, date utils, prediction API
├── flo_data.c            # Date math, storage, prediction engine
├── flo_views.h           # View allocation function declarations
├── flo_views.c           # Status, Calendar, and Log Period views
├── icons/                # App icon (10x10 PNG for launcher)
└── README.md

Notes

  • The app icon (icons/flo_10x10.png) needs to be a 10x10 pixel 1-bit PNG. You can create one with any image editor — a simple droplet or flower shape works well.
  • Data is stored at apps_data/flo_tracker/flo_data.bin on the SD card.