Xteink X4 Sample

A simple sample project for the Xteink X4 e-ink device using the GxEPD2 library.

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• Xteink eReader Community

Hardware

• Device: Xteink X4
• Board: ESP32-C3 (QFN32)
• Flash: 16MB (SPI), 6.5MB app0 / app1 partitions + spiffs
• RAM: 400KB (327680 bytes usable with PlatformIO, no PSRAM)
• Display: 4.26" E-Ink (800×480px, GDEQ0426T82, SSD1677 controller) (220PPI)
• Custom SPI pins: SCLK=8, MOSI=10, CS=21, DC=4, RST=5, BUSY=6
• Battery: 650mAh
• Storage: microSD card slot

Resources

• Hardware Schematics - XteinkX4 circuit diagrams
• Display Datasheet - 4.26" GDEQ0426T82 specifications

Features

• Basic GxEPD2 display initialization
• Custom SPI pin configuration
• Button input detection via ADC
• Simple text display examples

Building

# Build
platformio run

# Upload
platformio run -t upload

# Monitor
platformio device monitor

Firmware Backup & Restore

Backup Original Firmware

Before flashing custom firmware, back up the factory firmware:

# Read entire 16MB flash
python -m esptool --chip esp32c3 --port COM4 read_flash 0x0 0x1000000 firmware_backup.bin

# Read only app0 (faster)
python -m esptool --chip esp32c3 --port COM4 read_flash 0x10000 0x640000 app0_backup.bin

Restore Original Firmware

To restore the backed-up firmware:

# Write back the entire flash
python -m esptool --chip esp32c3 --port COM4 write_flash 0x0 firmware_backup.bin

# Write back only app0 (faster)
python -m esptool --chip esp32c3 --port COM4 write_flash 0x10000 app0_backup.bin

Important: Make sure to use the correct COM port for your device.

Switching Boot Partitions (app0/app1)

# Backup current OTA data first
python -m esptool --port COM4 read_flash 0xE000 0x2000 otadata_backup.bin

# Flash to switch boot partition
# Boot app0
python -m esptool --port COM4 write_flash 0xE000 otadata_boot_app0.bin

# Boot app1
python -m esptool --port COM4 write_flash 0xE000 otadata_boot_app1.bin

Notes

• This uses GxEPD2_426_GDEQ0426T82 as the display class for the 4.26" 800x480 display
• Display rotation is set to 3 (270 degrees)
• Partial refresh is used for button presses to improve responsiveness

Tasks

• Drive screen
• Read buttons
• Wakeup and deep sleep
• Read battery percentage
• Better rendering with grayscale support
• SD card reader
• WiFi
• Bluetooth

Button System

The XteinkX4 uses resistor ladder networks connected to two ADC pins for button detection. Each button press produces a unique analog voltage that's read via analogRead().

Button ADC Values

GPIO1 (4 buttons):

• Back: ~3470
• Confirm: ~2655
• Left: ~1470
• Right: ~3

GPIO2 (2 buttons):

• Volume Up: ~2205
• Volume Down: ~3

Power Button

GPIO3:

• Pressed: LOW
• This example uses a 1-second-long press for sleep and a 1-second-long press to wake from sleep

Battery Voltage

• GPIO0 is connected to the battery via a voltage divider (2x10K resistors), reading 1/2 of the actual voltage
• UART0_RXD/GPIO20 can be used to detect USB connection (charging or not)

microSD (TF) Card

SD SPI bus is shared with EPD, GPIO12 is used for CS (SS).

CS  (SS)    -> IO12
DO  (MISO)  -> IO7
DI  (MOSI)  -> IO10
SCK (SCLK)  -> IO8

Implementation Notes

• Use threshold ranges (e.g., value > 3200 && value < 3700) to detect button presses
• Add debouncing with edge detection (track last button state) to prevent multiple triggers
• Polling every 50ms works well for responsive input
• The resistor ladder allows multiple buttons on a single ADC pin, saving GPIO pins