The Watcher - ESP32-S3 E-Paper Timer

Minimal Pomodoro timer with Waveshare 4.2" e-paper (400×300, UC8176).

Hardware

• MCU: ESP32-S3-DevKitC-1 N8R8
• Display: Waveshare 4.2" V2 (400×300 B/W, UC8176)
• Buttons: GPIO 35, 36, 37
• Vibrator: GPIO 38

Pin Map

Display:  CS→10, DC→15, RST→16, BUSY→17, MOSI→11, SCK→12
Buttons:  Left→35, Mid→36, Right→37
Vibrator: PWM→38

Quick Start

# Pomodoro V2 Timer (buffer-isolated, recommended)
pio run -e pomodoro-v2 -t upload

# Simple countdown timer
pio run -e simple -t upload

# Button input test
pio run -e buttons -t upload

Libraries

Waveshare EPD

Location: lib/waveshare-epd/

Full-featured e-paper display library with:

• DEV_Config: Hardware initialization (GPIO/SPI)
• GUI_Paint: Drawing API (fonts, shapes, text)
• EPD_4IN2_V2: UC8176 controller driver
• Zero external dependencies
• UC8176 commands optimized

Example:

#include "EPD.h"
#include "GUI_Paint.h"

UBYTE *buffer = (UBYTE*)malloc(15000);
DEV_Module_Init();
EPD_4IN2_V2_Init();

Paint_NewImage(buffer, 400, 300, 0, WHITE);
Paint_SelectImage(buffer);
Paint_DrawString_EN(50, 50, "HELLO", &Font24, WHITE, BLACK);

EPD_4IN2_V2_Display(buffer);

Builds

Env	File	Lines	Description
pomodoro-v2	pomodoro_v2.cpp	750	Buffer-isolated Pomodoro (recommended)
simple	simple_timer_bitmap.cpp	384	Simple countdown timer
buttons	switch_observe.cpp	92	Button input test

UC8176 Controller

400×300 B/W e-paper driver:

• Full refresh: ~2s
• Partial refresh: ~400ms
• Anti-ghosting: Full refresh every 8 partials

Pomodoro V2 Features

• Buffer-isolated architecture: Dedicated buffers for each UI region
• Timer modes: 5, 10, 15, 20, 25 minutes
• 7-segment display: 70×130 pixel digits
• Progress visualization: 60 squares (1 per second)
• Haptic feedback: Vibrator alarm on completion
• Button controls:
  • Left (GPIO 35): START/PAUSE
  • Middle (GPIO 36): MODE select
  • Right (GPIO 37): RESET

See BUFFER_ARCHITECTURE.md for detailed implementation guide.

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Display: Waveshare 4.2" V2 | Controller: UC8176 | Resolution: 400×300