Cant run Hello world script on esp8266 on a 2.9 inch e-paper module

Other Hardware Displays
1

Hello,
i want to use the GxEPD2 libary and i have already uploaded the hello world example script and wired everything correctly as explained in the wiring example.h. but every time i get the error message 'display' was not declared in this scope;


// see GxEPD2_wiring_examples.h for wiring suggestions and examples
// if you use a different wiring, you need to adapt the constructor parameters!

// uncomment next line to use class GFX of library GFX_Root instead of Adafruit_GFX
//#include <GFX.h>

#include <GxEPD2_BW.h>
#include <GxEPD2_3C.h>
#include <GxEPD2_7C.h>
#include <Fonts/FreeMonoBold9pt7b.h>

// select the display class and display driver class in the following file (new style):
#include "GxEPD2_display_selection_new_style.h"

// or select the display constructor line in one of the following files (old style):
#include "GxEPD2_display_selection.h"
#include "GxEPD2_display_selection_added.h"

// alternately you can copy the constructor from GxEPD2_display_selection.h or GxEPD2_display_selection_added.h to here
// e.g. for Wemos D1 mini:
//GxEPD2_BW<GxEPD2_154_D67, GxEPD2_154_D67::HEIGHT> display(GxEPD2_154_D67(/*CS=D8*/ SS, /*DC=D3*/ 0, /*RST=D4*/ 2, /*BUSY=D2*/ 4)); // GDEH0154D67

void setup()
{
  //display.init(115200); // default 10ms reset pulse, e.g. for bare panels with DESPI-C02
  display.init(115200, true, 2, false); // USE THIS for Waveshare boards with "clever" reset circuit, 2ms reset pulse
  helloWorld();
  display.hibernate();
}

const char HelloWorld[] = "Hello World!";

void helloWorld()
{
  display.setRotation(1);
  display.setFont(&FreeMonoBold9pt7b);
  display.setTextColor(GxEPD_BLACK);
  int16_t tbx, tby; uint16_t tbw, tbh;
  display.getTextBounds(HelloWorld, 0, 0, &tbx, &tby, &tbw, &tbh);
  // center the bounding box by transposition of the origin:
  uint16_t x = ((display.width() - tbw) / 2) - tbx;
  uint16_t y = ((display.height() - tbh) / 2) - tby;
  display.setFullWindow();
  display.firstPage();
  do
  {
    display.fillScreen(GxEPD_WHITE);
    display.setCursor(x, y);
    display.print(HelloWorld);
  }
  while (display.nextPage());
}

void loop() {};

thanks in advance

2

That's correct, the display variable is not declared. The line

is commented. That line would declare the variable but you have to check if the used parameters match your situation. We don't know that because you provided absolutely no information about your hardware setup.

3

My first step is to always run the example(s) from the library you are using.

4

@maanpanel, Hi, welcome to the forum!

Most likely you have this e-paper module: 296x128, 2.9inch E-Ink display module.

For this module you would uncomment line 53 in GxEPD2_display_selection_new_style.h:

#define GxEPD2_DRIVER_CLASS GxEPD2_290_T94_V2 // GDEM029T94  128x296, SSD1680, (FPC-7519 rev.b), Waveshare 2.9" V2 variant

You could wire your module to your ESP8266 according to GxEPD2_wiring_examples.h.
Else you would need to adapt constructor parameters in line 134 of GxEPD2_display_selection_new_style.h:

// adapt the constructor parameters to your wiring
GxEPD2_DISPLAY_CLASS<GxEPD2_DRIVER_CLASS, MAX_HEIGHT(GxEPD2_DRIVER_CLASS)> display(GxEPD2_DRIVER_CLASS(/*CS=D8*/ EPD_CS, /*DC=D3*/ 0, /*RST=D4*/ 2, /*BUSY=D2*/ 4));

Good Luck!

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5

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