EpaperLite

ESP-IDF project for an ESP32 driving an SSD1619A 4.2-inch 400x300 black/white/red e-paper panel through hardware SPI.

The app displays a sectioned driver test page covering colors, geometry, pixels, bitmaps, UTF-8 Chinese text, and scaled image rendering.

Hardware

Default wiring:

ESP32	SSD1619A panel
GPIO18	SCL / SCK / CLK
GPIO23	SDA / DIN / MOSI
GPIO16	RES# / RST
GPIO17	D/C#
GPIO5	CS#
GPIO19	BUSY
3V3	VCC / VCI / VDDIO
GND	GND

Required strap pins:

Panel pin	Level	Meaning
BS1	GND	4-wire SPI
M/S#	3.3V	Single-chip master mode

Project Layout

.
├── CMakeLists.txt
├── main
│   ├── CMakeLists.txt
│   ├── main.c
│   ├── epd_image.h
│   └── drivers
│       └── epd
│           ├── epd_ssd1619a.c
│           ├── epd_ssd1619a.h
│           ├── sarasa_subset.c
│           └── sarasa_subset.h

main/assets/fonts/SarasaMonoSC.c is intentionally ignored by Git because the full LVGL-generated font is large and makes the firmware exceed the default 1 MB app partition. The firmware uses sarasa_subset.c, a compact subset generated from that font.

Build And Flash

Use an ESP-IDF shell:

idf.py set-target esp32
idf.py build
idf.py -p COMx flash monitor

Replace COMx with your serial port.

Driver Usage

Include the driver:

#include "epd_ssd1619a.h"

Minimal full-screen flow:

ESP_ERROR_CHECK(epd_init());

epd_clear(EPD_COLOR_WHITE);
epd_draw_text_utf8(20, 20, "中文测试", EPD_COLOR_BLACK);
epd_draw_rect(10, 10, EPD_WIDTH - 20, EPD_HEIGHT - 20, EPD_COLOR_RED);

ESP_ERROR_CHECK(epd_display_framebuffer());

The framebuffer color model uses two 1-bit planes:

Color	BW RAM	RED RAM
White	1	0
Black	0	0
Red	0	1

Drawing APIs

Framebuffer and primitive drawing:

void epd_clear(epd_color_t color);
void epd_set_pixel(int x, int y, epd_color_t color);
void epd_draw_hline(int x, int y, int w, epd_color_t color);
void epd_draw_vline(int x, int y, int h, epd_color_t color);
void epd_draw_line(int x0, int y0, int x1, int y1, epd_color_t color);
void epd_draw_rect(int x, int y, int w, int h, epd_color_t color);
void epd_fill_rect(int x, int y, int w, int h, epd_color_t color);
void epd_draw_circle(int x0, int y0, int r, epd_color_t color);
void epd_fill_circle(int x0, int y0, int r, epd_color_t color);

Text:

void epd_draw_string_5x7(int x, int y, const char *s, epd_color_t color, int scale);
void epd_draw_text_utf8(int x, int y, const char *s, epd_color_t color);

epd_draw_text_utf8() currently supports the compact Sarasa subset used by the demo: 中 文 测 试 驱 动 字 图 片, plus ASCII fallback via the built-in 5x7 font.

Bitmaps:

void epd_draw_bitmap_1bpp(...);
void epd_draw_bitmap_2plane(...);
void epd_draw_bitmap_2plane_fit(...);

epd_draw_bitmap_2plane_fit() keeps aspect ratio and uses nearest-neighbor scaling, useful for showing a large 400x300 image in a smaller box:

epd_draw_bitmap_2plane_fit(
    290, 155,
    76, 44,
    EPD_IMAGE_WIDTH,
    EPD_IMAGE_HEIGHT,
    epd_image_bw,
    epd_image_red
);

Refresh And Power APIs

esp_err_t epd_display_framebuffer(void);
esp_err_t epd_display_area(int x, int y, int w, int h);
void epd_set_update_control(uint8_t control2);
esp_err_t epd_set_frame_rate(uint16_t hz);
esp_err_t epd_write_lut(const uint8_t *lut, uint32_t len);
esp_err_t epd_deep_sleep(void);
esp_err_t epd_deep_sleep_mode(epd_deep_sleep_mode_t mode);

Notes:

• SPI is configured for 20 MHz hardware SPI, matching the SSD1619A write-speed limit.
• epd_display_area() writes only a clipped rectangular RAM window. The X range expands to 8-pixel boundaries because SSD1619A RAM X addressing is byte based.
• Custom LUTs are panel-specific. Use epd_write_lut() only with known-good waveform data for your panel.
• Exiting deep sleep requires a hardware reset.

Display Data Flow

1. Draw into the ESP32-side framebuffer.
2. Send the black/white plane with command 0x24.
3. Send the red plane with command 0x26.
4. Select the update sequence with command 0x22.
5. Start the refresh with command 0x20.
6. Wait for BUSY to become inactive.

The MCU only prepares and sends image RAM. The SSD1619A uses its waveform/LUT and high-voltage driver blocks to physically move the e-paper pigment.