[SOLVED] read String data to an arduino from a header file (waveshare Eink)

read String data to an arduino from a header file (waveshare Eink)

Geetings, Im trying to read String files to an arduino from a header file (.h). Its compiling fine but i cant call the string. When I serial print the string only gibberish shows up on the monitor. This is my arduino Code:

#include <epd4in2.h>
#include <epdif.h>
#include <epdpaint.h>
#include <fonts.h>

#include <SPI.h>
#include "epd4in2.h"
#include "imagedata.h"
#include "epdpaint.h"

#include "list.h"

#define COLORED     0
#define UNCOLORED   1

String test1;
String test2;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  Serial.print("port test");

  Epd epd;

  if (epd.Init() != 0) {
    Serial.println("e-Paper init failed");
    return;
  }

  test1 = String(DATA_1[0]);\
  Serial.println(test1);
  test2 = String(DATA_1[1]);
  Serial.println(test2);

  /* This clears the SRAM of the e-paper display */
  epd.ClearFrame();

 /* Due to RAM not enough in Arduino UNO, a frame buffer is not allowed. */
 unsigned char image[1500];
 Paint paint(image, 400, 28);    //width should be the multiple of 8 

 paint.Clear(UNCOLORED);
 paint.DrawStringAt(0, 0, "test1", &Font24, COLORED);
 epd.SetPartialWindow(paint.GetImage(), 100, 40, paint.GetWidth(), 
 paint.GetHeight());

 paint.Clear(COLORED);
 paint.DrawStringAt(100, 2, "test2", &Font24, UNCOLORED);
 epd.SetPartialWindow(paint.GetImage(), 0, 64, paint.GetWidth(), 
 paint.GetHeight());

 /* This displays the data from the SRAM in e-Paper module */
 epd.DisplayFrame();

 /* Deep sleep */
 epd.Sleep();
 }

void loop() {
  // put your main code here, to run repeatedly:

}

and here the data in the .h file:

extern const String DATA_1[] PROGMEM = { "bat", "2244"}; 
extern const String DATA_2[] PROGMEM = { "bmp", "15662"}; 
extern const String DATA_3[] PROGMEM = { "docx", "16670"}; 
extern const String DATA_4[] PROGMEM = { "jpg", "150645"}; 
extern const String DATA_5[] PROGMEM = { "mp3", "9882324"}; 
extern const String DATA_6[] PROGMEM = { "txt", "807"}; 
extern const String DATA_7[] PROGMEM = { "url", "118"};

I created this list using a .bat script.

Im pretty new to this so any help would be appreciated. Kind Regards Luigi

Solution

When you use PROGMEM, the initialised value is stored in the program memory, and a pointer to the location is given to the variable.

But when you use

test1 = String(DATA_1[0]);

the code searches with the same address in the ram and not the program memory.

You can read about it here. https://www.nongnu.org/avr-libc/user-manual/pgmspace.html

I have faced the same problem before, but I was storing bytes, not strings. So I was able to get away with using pgm_read_byte. You may have to put in some effort to make the program work.

I hope this helps and Good luck.