The code

Published January 23, 2022 © GPL3+

E-paper display using partial updates

In this tutorial I show you how to make partial updates on your E-paper display using the GxEPD2 library.

IntermediateFull instructions provided14,860

Things used in this project

Hardware components

Espressif ESP32

You can use any ESP32 board

2.9inch E-Ink display module

Story

In this tutorial I show you how make a partial update of an E-paper display using the GxEPD2 library.

Because E-ink screens have a very slow refresh rate (for example the 2.9inch screen from Waveshare 2s for a full refresh) the partial refresh feature can be very useful. The screen I am using has a partial refresh time of 0.3 seconds.

First of all the e-ink display needs to be connected to the ESP32. The wiring can be different between the ESP32 boards. Here are a few examples from an example sketch for the GxEPD2 libarary:

// mapping suggestion for ESP32, e.g. LOLIN32, see .../variants/.../pins_arduino.h for your board
// NOTE: there are variants with different pins for SPI ! CHECK SPI PINS OF YOUR BOARD/
/ BUSY -> 4, RST -> 16, DC -> 17, CS -> SS(5), CLK -> SCK(18), DIN -> MOSI(23), GND -> GND, 3.3V -> 3.3V// mapping of Waveshare ESP32 Driver Board
// BUSY -> 25, RST -> 26, DC -> 27, CS-> 15, CLK -> 13, DIN -> 14
// NOTE: this board uses "unusual" SPI pins and requires re-mapping of HW SPI to these pins in SPIClass
//       see example GxEPD2_WS_ESP32_Driver.ino, it shows how this can be done easily
// mapping suggestion for ESP32, e.g. LOLIN32 D32 PRO
// BUSY -> 15, RST -> 2, DC -> 0, CS -> 5, CLK -> SCK(18), DIN -> MOSI(23), GND -> GND, 3.3V -> 3.3V
// note: use explicit value for CS, as SS is re-defined to TF_CS(4) in pins_arduino.h for Board: "LOLIN D32 PRO"// mapping suggestion for ESP32, e.g. TTGO T8 ESP32-WROVER
// BUSY -> 4, RST -> 0, DC -> 2, CS -> SS(5), CLK -> SCK(18), DIN -> MOSI(23), GND -> GND, 3.3V -> 3.3V
// for use with Board: "ESP32 Dev Module":

I have a NodeMCU ESP32 so I connected it as follows (display --> ESP32): BUSY --> D4, RST --> RX2, DC --> TX2, CS --> D5, CLK --> D18, DIN --> D23, GND --> GND, VCC --> 3V3

The code

First of all you need to install the libraries GxEPD2 and U8g2_for_Adafruit_GFX (Sketch --> Include Library --> Manage Libraries --> search for the name of the library --> click install).

Watch the video above for more information on the code.

Code

e-ink_partial_update

#define ENABLE_GxEPD2_GFX 0

#include <GxEPD2_BW.h> // including both doesn't use more code or ram
#include <GxEPD2_3C.h> // including both doesn't use more code or ram
#include <U8g2_for_Adafruit_GFX.h>

//if you have another microcontroller or another e-ink display module you have to change the following line
GxEPD2_BW<GxEPD2_290_T94_V2, GxEPD2_290_T94_V2::HEIGHT> display(GxEPD2_290_T94_V2(/*CS=5*/ SS, /*DC=*/ 17, /*RST=*/ 16, /*BUSY=*/ 4)); // GDEM029T94, Waveshare 2.9" V2 variant

U8G2_FOR_ADAFRUIT_GFX u8g2Fonts;

void setup()
{
  display.init();
  display.setTextColor(GxEPD_BLACK);
  display.firstPage();
  display.setRotation(1);

  u8g2Fonts.begin(display); // connect u8g2 procedures to Adafruit GFX
  delay(1000);

  uint16_t bg = GxEPD_WHITE;
  uint16_t fg = GxEPD_BLACK;
  u8g2Fonts.setForegroundColor(fg);         // apply Adafruit GFX color
  u8g2Fonts.setBackgroundColor(bg);

  do{
    display.fillScreen(GxEPD_WHITE);

    u8g2Fonts.setFont(u8g2_font_fub20_tr);   //font is set
    u8g2Fonts.setCursor(20, 80);             //cursor(x,y)
    u8g2Fonts.print("Millis: ");   //print the text
  }while (display.nextPage());
}


void loop() {
  display.setPartialWindow(115, 50, 200, 40);
  display.firstPage();

  do{
    display.fillScreen(GxEPD_WHITE);
    u8g2Fonts.setCursor(120, 80);
    u8g2Fonts.print(millis());
  }while(display.nextPage());
}

Credits

galoebn

9 projects • 4 followers

E-paper display using partial updates

Things used in this project

Hardware components

Story

The code

Schematics

Schematics

Code

e-ink_partial_update

Credits

galoebn

Comments

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E-paper display using partial updates

E-paper display using partial updates

Things used in this project

Hardware components

Story

The code

Schematics

Schematics

Code

e-ink_partial_update

Credits

galoebn

Comments

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