tanvirbinzahid/Smart-Flood-Early-Warning-System-STM32 ? reverse-engineered prompt

Build me a smart flood early warning system for an STM32 Blue Pill board that watches water level, soil moisture, temperature, and humidity in real time and turns that into a simple risk score from 0 to 100.

I want it to use an ultrasonic sensor for water level, a DHT11 for temperature and humidity, and an analog soil moisture sensor. Show the current readings and risk status on a small OLED screen, and drive a clear 3 level alert flow with SAFE, WARNING, and EVACUATE using LEDs plus a buzzer. The risk should update continuously and feel stable, so please include sensible filtering and trend detection instead of raw noisy readings.

It should also let me control things from a 4 by 4 keypad, like switching display pages, muting the alarm, adjusting sensitivity, and tweaking calibration values. Please include session min and max stats and a basic power save behavior when conditions stay safe for a while.

If anything is unclear, look up the current STM32 docs and wire it up cleanly end to end.