117 lines
5.2 KiB
Markdown
117 lines
5.2 KiB
Markdown
# Weather Predictor
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An autonomous **barometric weather station** built on a Wemos D1 mini (ESP8266).
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It reads atmospheric pressure and temperature, keeps accurate battery-backed
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time, and predicts near-term local weather entirely on-device using the
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**Zambretti algorithm** — no internet forecast service required. Readings and
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the forecast are shown on a small TFT and on a self-hosted web interface styled
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as a barometer instrument.
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## Features
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- **Local Zambretti forecast** from the 3-hour sea-level pressure trend (rising / steady / falling), adjusted for season.
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- **On-device TFT screen** (160×80): time, date, pressure with trend arrow, temperature, a scaled weather icon, and the station's Wi-Fi/IP.
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- **Web interface** served from the device (no external CDNs, works offline):
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- live barometer dial with a needle and a "set hand" ghost at the pressure 3 h ago;
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- barograph of pressure & temperature with labelled axes;
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- **forecast change log**;
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- settings with **city presets** and a UTC-offset time-zone picker.
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- **Persistence** in LittleFS: settings, pressure history, and the forecast log all survive reboots.
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- **Wi-Fi provisioning** via WiFiManager (captive portal — no credentials in code) and **NTP** time sync to the DS3231.
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## Hardware
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| Component | Part | Bus / notes |
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|-----------|------|-------------|
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| MCU | Wemos D1 mini (ESP8266, 4 MB flash) | — |
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| Pressure & temperature | BMP180 (GY-68) | I²C, addr `0x77` |
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| Real-time clock | DS3231 (HW-022, battery-backed) | I²C, addr `0x68` |
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| Display | 0.96" 80×160 TFT, ST7735S | 4-wire SPI, run landscape 160×80 |
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### Wiring
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The display uses hardware SPI; the two I²C modules share one bus.
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| Signal | Wemos pin | GPIO |
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|--------|-----------|------|
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| TFT CS | D8 | 15 |
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| TFT DC | D3 | 0 |
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| TFT RST | D4 | 2 |
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| TFT SDA (MOSI) | D7 | 13 |
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| TFT SCL (SCK) | D5 | 14 |
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| TFT BLK (backlight) | D2 | 4 |
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| I²C SDA (BMP180 + DS3231) | D6 | 12 |
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| I²C SCL (BMP180 + DS3231) | D1 | 5 |
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All modules run on 3.3 V / GND. I²C is started with `Wire.begin(D6 /*SDA*/, D1 /*SCL*/)`.
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## Build & flash (Arduino IDE)
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1. Install the **ESP8266** board package; select board **"LOLIN(WEMOS) D1 R2 & mini"**.
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2. Set **Tools → Flash Size** to a layout with a filesystem, e.g. **4MB (FS:2MB)**.
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3. Install libraries via Library Manager:
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*Adafruit GFX*, *Adafruit ST7735 and ST7789*, *Adafruit BMP085*, *RTClib*,
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*ArduinoJson* (v7.x), *WiFiManager* (by tzapu).
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`ESP8266WiFi`, `ESP8266WebServer`, `LittleFS`, `Wire`, `SPI`, `time` ship with the core.
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4. Open `WeatherPredictor/WeatherPredictor.ino` and upload.
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## First run
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1. On first boot the device opens a Wi-Fi access point **`WeatherPredictor-Setup`**.
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Join it from a phone and pick your network in the captive portal.
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2. After connecting, the device syncs time over NTP and writes it to the DS3231.
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3. The screen and Serial (115200) print the station's IP — open `http://<ip>/`.
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4. The forecast shows **"Collecting data…"** until ~3 h of pressure history exists;
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that is expected — the Zambretti method needs a trend before its first call.
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Set your **altitude** in the web settings (or pick a city preset): sea-level
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pressure — and therefore the forecast — depends on it (~0.12 hPa per metre).
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## REST API
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| Endpoint | Method | Returns |
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|----------|--------|---------|
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| `/` | GET | Web UI |
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| `/api/current` | GET | time, pressure (abs + sea level), temperature, trend, forecast |
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| `/api/history` | GET | recent pressure/temperature samples |
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| `/api/forecasts` | GET | forecast change log (newest first) |
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| `/api/settings` | GET / POST | altitude, time-zone offset, coordinates |
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## Project structure
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```
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WeatherPredictor/
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WeatherPredictor.ino scheduler; wires the modules together
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config.h pins, addresses, intervals, defaults
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state.h shared current-readings struct
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sensors.* BMP180 read + sea-level conversion
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rtc_time.* DS3231 read/set + NTP sync
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display_ui.* ST7735 rendering + weather icons
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forecast.* Zambretti forecast + trend classification
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history.* pressure ring buffer + LittleFS persistence
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flog.* forecast change log
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app_settings.* settings struct + LittleFS JSON
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net.* WiFiManager connection
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web_server.* HTTP server + REST API
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web_page.h web UI (HTML/CSS/JS) in PROGMEM
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docs/superpowers/ design spec and implementation plan
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```
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## Notes & gotchas
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- **BGR panel:** this 0.96" ST7735S has red/blue swapped, so colours are built
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R/B-exchanged in `display_ui.cpp`. If your panel looks wrong, adjust there
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(and the `invertDisplay` / `setRotation` in `displayBegin()`).
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- **Restrictive networks:** on some LANs the router does not resolve external
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hostnames, so NTP uses hard-coded Cloudflare/Google anycast IPs instead of
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names. Such networks may also block SSH.
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- **Flash wear:** history is flushed every 15 min and the forecast log only on
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change, so LittleFS wear leveling keeps flash life at years/decades.
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## Credits
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Zambretti forecast constants and lookup tables adapted from
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[G6EJD's ESP Zambretti forecaster](https://github.com/G6EJD/ESP32_Weather_Forecaster_TN061).
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