Connections and Components:

Wiring:

DeskClock.ino (ESP32 firmware)

• Libraries: Adafruit GFX, Adafruit ST7735, ArduinoJson 7.x, LittleFS (custom wallpaper and unsent sessions) and the ESP32 core’s FreeRTOS and timer support.
• Display: every frame is drawn into a 128×160 off-screen buffer, then sent to the screen in one go, which avoids flicker. A background layer holds the wallpaper, dimmed per screen.
• Screens: one screen enum with a draw function and an input handler for each, using shapes and fonts from Adafruit GFX. The built-in wallpapers are drawn in code.
• Input: a 1 kHz FreeRTOS task reads and debounces the encoder. Buttons are polled with short and long press detection, and everything goes into a small event queue.
• Timer: it runs on the ESP32’s own clock. Sessions are saved to flash if the PC is not connected, and re-sent until the PC acknowledges them.
• Clock and stats: the time comes from the PC, which sends the time and time-zone offset. The device keeps counting from there.
• Serial protocol: newline-delimited JSON at 115200 baud (PING, GET_STATUS, SYNC_TIME, SET_CONFIG, CONTROL, EVENT_ACK). Wallpaper upload uses binary chunks with sequence numbers and CRC16, then an end command.

Desk Clock.py (Windows tray app)

• Libraries: pyserial (talks to the ESP32), pystray (tray icon and menu), Pillow (tray icon and wallpaper conversion). The rest is the Python standard library: threading, queue, json, csv, subprocess, logging.
• Threads: a worker thread runs all menu actions, so the tray never freezes. A reader thread owns serial input, and a supervisor thread handles auto-connect, a heartbeat and an hourly clock sync.
• Connection: it skips Bluetooth COM ports, finds the board by sending a PING, and doesn’t reset the ESP32 on connect.
• Wallpaper: it centre-crops and resizes the image to 128×160, converts it to RGB565, and sends 1 KB chunks with CRC and retry.
• Data: finished sessions go to desk_clock_data.json and desk_clock_sessions.csv, without duplicates. Errors are written to desk_clock.log.