Skip to content

README.md

Latest commit

 

History

History
348 lines (264 loc) · 8.58 KB

README.md

File metadata and controls

348 lines (264 loc) · 8.58 KB

E-Paper Watch Documentation

Complete documentation for the e-paper watch project.

Documentation Index

Features

  • Display: 200×200 monochrome e-paper (1.54", 200 DPI)
  • Watchfaces: 54+ pre-configured with custom fonts
  • Time Keeping: DS3231 RTC (±2 minutes/year accuracy)
  • Refresh Modes: Partial (fast) and full (ghosting-free)
  • Development Tools: Python scripts for creating custom watchfaces

Configuration

Main Settings

Edit epaper_watch.ino to customize behavior:

// Enable/disable features
const bool ENABLE_WATCHFACE_CYCLING = true;  // Auto-cycle every 10 mins
const bool ENABLE_PARTIAL_REFRESH = true;    // Fast updates
const bool ENABLE_SERIAL_DEBUG = false;      // Disable for battery life

// Timing
const uint8_t FULL_REFRESH_INTERVAL = 10;    // Minutes (10 = :00, :10, :20...)
const uint8_t WAKE_BEFORE_MINUTE_SEC = 57;   // Wake at :57s (3s poll window)
const uint16_t POLL_INTERVAL_MS = 200;       // Poll every 200ms

Power Optimization

Maximum Battery Life:

const uint8_t WAKE_BEFORE_MINUTE_SEC = 50;  // 10-second window
const uint16_t POLL_INTERVAL_MS = 300;       // Poll every 300ms
const bool ENABLE_SERIAL_DEBUG = false;      // Disable serial

Balanced - Default:

const uint8_t WAKE_BEFORE_MINUTE_SEC = 57;  // 3-second window
const uint16_t POLL_INTERVAL_MS = 200;       // Poll every 200ms
const bool ENABLE_SERIAL_DEBUG = false;      // Disable serial

Fast Response:

const uint8_t WAKE_BEFORE_MINUTE_SEC = 59;  // 1-second window
const uint16_t POLL_INTERVAL_MS = 100;       // Poll every 100ms

Creating Custom Watchfaces

Using Python Tools (Recommended)

cd watchfaceutils

# Interactive configurator with live preview
python3 configure_watchface.py

# Test single watchface
python3 render_watchface.py \
  --watchface ../mywatchfaces/custom.h \
  --time-font ../myfonts/Font20pt7b.h \
  --date-font ../myfonts/Font10pt7b.h \
  --output custom_preview.png

# Generate all previews
python3 generate_all_previews.py

Manual Configuration

Step 1: Prepare 200×200 monochrome image

Step 2: Convert to bitmap array using image2cpp

Step 3: Create watchface header file

// mywatchfaces/custom.h
const unsigned char custom_bitmap[] PROGMEM = {
  // ... bitmap data ...
};

// Required array wrapper
static const int custom_bitmap_allArray_LEN = 1;
static const unsigned char* custom_bitmap_allArray[1] = {
  custom_bitmap
};

// WatchFace class
struct WatchFace_custom : public WatchFace {
  WatchFace_custom() {
    bitmap = custom_bitmap;
    layout = 1;              // 0=single-line, 1=two-line

    // Time positioning
    text1x = -1;             // -1=center, 0-100=percentage
    text1y = 40;             // 40% from top
    text1font = &Font20pt7b;

    // Date positioning
    text2x = -1;
    text2y = 60;             // 60% from top
    text2font = &Font10pt7b;
  }
};

Step 4: Include in myutils.h

#include "mywatchfaces/custom.h"

Step 5: Add to epaper_watch.ino

WatchFace* allWatchFaces[] = {
  // ... existing watchfaces ...
  new WatchFace_custom(),
};

📖 Complete API Reference →

Watchface Gallery

📸 View All 54 Watchfaces →

Preview of available watchfaces:


AT-AT
Harry Potter
Planets

Beatles Penguins
Hogwarts
Guitar

Collections: Star Wars (6) • Harry Potter (6) • Club Penguin (6) • Animals (9) • Characters (14) • Music (3) • Nature (5) • Patterns (3) • Cultural (2)

Troubleshooting

Display Issues

Display not updating

  • Check SPI connections (MOSI, SCK, CS, DC, RST, BUSY)
  • Verify 3.3V power supply
  • Try disabling partial refresh: const bool ENABLE_PARTIAL_REFRESH = false;

Display is garbled

  • Verify correct model (GDEH0154D67)
  • Check ground connection
  • Ensure proper SPI wiring

Ghosting artifacts

  • Increase full refresh frequency: const uint8_t FULL_REFRESH_INTERVAL = 5;
  • Temperature affects ghosting (worse in cold)

RTC Issues

Time is incorrect after upload

  • Enable time setup: const bool ENABLE_TIME_SETUP = true;
  • Upload and open Serial Monitor (115200 baud)
  • Follow prompts to set time

RTC not detected

  • Verify I2C connections (SDA, SCL)
  • Check I2C address (0x68)
  • Test with I2C scanner
  • Try different RTC module

Power Issues

Battery drains too quickly

  1. Disable serial debug: const bool ENABLE_SERIAL_DEBUG = false;
  2. Optimize wake time: const uint8_t WAKE_BEFORE_MINUTE_SEC = 50;
  3. Check for shorts or bad connections
  4. Measure current with multimeter

Time updates miss minute changes

  1. Increase polling window: const uint8_t WAKE_BEFORE_MINUTE_SEC = 55;
  2. Decrease poll interval: const uint16_t POLL_INTERVAL_MS = 100;

Compilation Errors

"library not found"

  • Install missing library via Library Manager

"multiple definition"

  • Ensure bitmap arrays in watchface files have static keyword: 
    static const unsigned char* bitmap_allArray[1] = { ... };

"struct redefinition"

  • Check for duplicate struct names
  • Ensure watchface files included only once

Performance Metrics

Memory Usage

Flash (1MB total):        ~800KB used (78%)
  - Sketch:               ~85KB
  - Libraries:            ~68KB
  - Fonts (66):           ~380KB
  - Watchfaces (54):      ~270KB

RAM (256KB total):        ~23KB used (9%)
  - Global variables:     ~12KB
  - Display buffer:       ~5KB
  - Stack:                ~4KB

Power Consumption

Mode Current Notes
Deep Sleep ~50µA Between polling windows
Active Polling ~1mA Last 3 seconds of each minute
Display Partial ~5mA 200-500ms duration
Display Full ~8mA 1-2s duration every 10 mins
Average 200-500µA Typical usage

Timing

Operation Duration
Partial refresh 200-500ms
Full refresh 1-2s
Text rendering 50-100ms
Bitmap drawing 100-200ms
RTC read <1ms

Adding/Removing Watchfaces

Add a Watchface

  1. Create header file in mywatchfaces/
  2. Include in myutils.h: 
    #include "mywatchfaces/your_watchface.h"
  3. Add to array in epaper_watch.ino: 
    WatchFace* allWatchFaces[] = {
  // ... existing ...
  new WatchFace_your_watchface(),
};

Remove a Watchface

  1. Comment out in epaper_watch.ino: 
    // new WatchFace_unused(),
  2. Optionally comment out include in myutils.h to save memory

Development Tools

Python Scripts

configure_watchface.py: Interactive step-by-step configurator

  • Select watchface and fonts
  • Position text interactively
  • Generate C++ code
  • Save configuration

render_watchface.py: Command-line renderer for testing

  • Render single watchface
  • Test different positions
  • Generate preview images

generate_all_previews.py: Batch preview generator

  • Generate all watchface previews
  • Auto-detects configurations
  • Useful for documentation

Python Requirements

pip3 install Pillow

Technical Specifications

Specification Details
MCU Nordic nRF52840 (ARM Cortex-M4, 64MHz, 1MB Flash, 256KB RAM)
Display GoodDisplay GDEH0154D67 (1.54", 200×200, SPI, E-Ink)
RTC Maxim DS3231 (I2C, TCXO, ±3.5ppm)
Power 3.7V LiPo, 300-500mAh recommended
Update Latency <3 seconds during watch face refresh
Refresh Rate Partial updates every minute, full every 10 minutes