Dynamic Electricity Price Ticker (XIAO ESP32C3)

This project displays day-ahead electricity prices for Slovenia (Energy-Charts API) on a 20x4 I2C LCD using a XIAO ESP32C3. It shows hourly averages and 15-minute detail for the current hour, and uses a white LED as a visual price indicator.

Features

• Fetches day-ahead prices from Energy-Charts API (bzn=SI)
• Displays current hour 15-minute detail on row 0 and hourly averages on remaining rows
• LED patterns indicate price ranges (breathing, steady, blink, double-blink, triple-blink)
• Wi‑Fi provisioning mode (AP + simple web UI)
• Automatic NTP sync and DST-aware local time (CET/CEST for Ljubljana)

Important: DST / Timezone

The firmware initializes timezone with the CET/CEST POSIX TZ string so localtime() and conversions of API unix timestamps respect DST transitions for Ljubljana:

configTzTime("CET-1CEST,M3.5.0/02:00,M10.5.0/03:00", "pool.ntp.org");

Hardware and Pinout

• Board: Seeed XIAO ESP32C3 (or compatible ESP32-C3 board)

Pin usage (GPIO - function):

• GPIO4 - Button (pushbutton to GND, internal pull-up enabled in code)
• GPIO5 - White LED (use series resistor ~220-470Ω)
• GPIO9 - Presence sensor (RCWL-0516) OUT
• GPIO21 - Built-in status LED (WiFi indicator)
• I2C (SDA / SCL) - LCD (LiquidCrystal_I2C), default address 0x27

Presence sensor (RCWL-0516) wiring

• VCC -> 3.3V
• GND -> GND
• OUT -> GPIO9
• Crucial: add a 10kΩ pull-down resistor between GPIO9 (OUT) and GND.
  • Why: The RCWL-0516 output may float or remain high on boot; the pull-down ensures a defined LOW when idle and prevents the LCD backlight from unintentionally turning off or on.
  • If you do not use a presence sensor, the firmware keeps the backlight ON by default.

Button wiring

• One leg of the pushbutton to GPIO4, the other to GND. The code uses INPUT_PULLUP, so no external resistor is required.

White LED wiring

• GPIO5 -> 220Ω resistor -> LED anode
• LED cathode -> GND

I2C LCD wiring

• SDA -> board SDA pin
• SCL -> board SCL pin
• VCC -> 5V or 3.3V depending on module
• GND -> GND

Software

• Espressif ESP32 Arduino core (tested with esp32 by Espressif Systems v3.3.2 in Arduino IDE)
• ArduinoJson library

Notes

• The project stores Wi‑Fi credentials in non-volatile storage (Preferences) and falls back to an AP provisioning portal if no credentials are saved.
• The code applies power company fees and VAT to convert wholesale EUR/MWh prices to final consumer EUR/kWh by default. You can disable fees by setting APPLY_FEES_AND_VAT to false.

How to use

1. Upload the firmware to your XIAO ESP32C3.
2. If no Wi‑Fi credentials are stored, the board will start an AP MyTicker_Setup — connect and open the provisioning web UI.
3. After Wi‑Fi and NTP sync, the sketch will fetch prices and start displaying them.

License

• Add license information here if you want to publish this repository.