Image header file on SD-card¶

The image header file on SD-card library saves the screen as a header file on the SD-card.

The header file is added to the source code and included in the project of the application statically at build-time. Once the application is built, it loads the image into the frame-buffer, ready to be displayed dynamically at run-time.

This option only supports the monochrome screens.

Info

This method is not recommended for MCUs, as the management of the SD-card is rather slow and prone to interferences.

The image on SD-card library is available on the Commercial edition.

Danger

Because the file library manages windows, it requires a screen of type Screen_EPD_EXT3_Fast provided by the PDLS_EXT3_Advanced_Fast, PDLS_EXT3_Advanced_Wide or PDLS_EXT3_Advanced_Touch libraries.

Configure¶

Warning

Ensure the screen is declared and initialised according to the configuration procedure.

#include "hV_File_Image.h"

The pre-processor statement includes the file library. It should be mentioned after the statement for the screen library.

Danger

This library requires the external SD library to manage the SD-card.

Ensure the external SD library is installed and configured properly.

File_Image myFile(&myScreen);

The constructor File_Image() sets the link to the screen. It should be mentioned after the constructor of the screen.

uint8_t result = myFile.beginFileSystem(pinCS,
    portSPI,
    pinDetect,
    pinLevel);

if (result != RESULT_SUCCESS)
{
    hV_HAL_Serial_crlf();
    hV_HAL_log(LEVEL_CRITICAL, "SD-card error");
    hV_HAL_exit(0x01);
}

result = myFile.setFolder("Image");

beginFileSystem() checks an SD-card is available and initialises it.

The required parameter is

The first line sets the pin for selecting the SD-card.

It is easily provided with myScreen.getBoardPins().cardCS.

The optional parameters are

The second line sets the number of the SPI port, 0 by default;
The third line sets the pin for the detect signal, NOT_CONNECTED or -1 par default;
The fourth line sets the level of detect signal, LOW by default.

The function returns RESULT_SUCCESS if successful, RESULT_ERROR otherwise.

To obtain the pin for selecting the SD-card, use

uint8_t pinCardCS = myScreen.getBoardPins().cardCS;
uint8_t result = myFile.beginFileSystem(pinCardCS);

setFolder() sets the name of the folder for the files, and creates it if it does not exists.

By default, the files are located under the folder img.

The function returns RESULT_SUCCESS if successful, RESULT_ERROR otherwise.

Use¶

Generate¶

uint8_t result = myFile.saveScreen("File_Image");

saveScreen() saves the screen on the SD-card as a image header file.

The function returns RESULT_SUCCESS if successful, RESULT_ERROR otherwise.

The required parameter is

The first line provides the name of the file without the .h extension.

myFile.saveWindow("File_Image",
    40, 71, 100, 50) // x y dx dy

saveWindow() save a window on a header file on the SD-card as an image.

The required parameters are

The first line provides the name of the file without the .h extension.
The second line defines the window with vector coordinates.

The coordinates are rounded as multiple of 8.

For example, the vector coordinates (70, 44, 155, 64) are changed to (70, 40, 155, 72).

The resulting header file is named File_Image.h and contains the structure Image_File_Image.

The function returns RESULT_SUCCESS if successful, RESULT_ERROR otherwise.

uint8_t result = myFile.endFileSystem();

endFileSystem() closes the SD-card.

The function returns RESULT_SUCCESS if successful, RESULT_ERROR otherwise.

Display¶

// Image
#include "File_Image.h"

uint8_t result;
result = myFile.readScreen(Image_File_Image);
if (result == RESULT_SUCCESS)
{
    myScreen.flush();
    wait(4);
}

The application needs to include the header file previously generated.

readScreen() loads the image into the frame-buffer, ready to be displayed.

The header file can also be read with the Serial_Image object, from the 16-bit image implementation on the Serial library.

The function returns RESULT_SUCCESS if successful, RESULT_ERROR otherwise.

Example¶

This is the core of the code from example File_Write_Image.ino.

First, generate the header file.

void displayWriteImage()
{
    // Initialise
    uint8_t result;
    result = myFile.beginFileSystem(5);
    if (result != RESULT_SUCCESS)
    {
        hV_HAL_log(LEVEL_ERROR, "SD-card error");
        hV_HAL_Serial_crlf();
        return;
    }

    myScreen.setOrientation(myOrientation);
    myScreen.selectFont(fontLarge);

    myScreen.clear();
    myScreen.gText(8, 8, "File Image");
    myScreen.flushFast();

    // Write to SD-card
    result = myFile.saveScreen("File_Image");
    wait(4);
}

The generated header file contains the image as a structure.

// Image as header file generated by hV_File_Image

// SDK
#include "hV_HAL_Peripherals.h"

// Release
#ifndef FILE_IMAGE_RELEASE
#define FILE_IMAGE_RELEASE

#include "hV_Image.h"

static const uint8_t Table_File_Image[] =
{
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // v= 0
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // v= 1
   // ...
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // v= 263
};

const image_s Image_File_Image =
{
  .minWindowH = 0,
  .minWindowV = 0,
  .maxWindowH = 175,
  .maxWindowV = 263,
  .depth = 2,
  .size = 5808,
  .table = Table_File_Image
};

#endif // FILE_IMAGE_RELEASE

The window uses rectangular coordinates.

Then, include the header file in the application and build it.

// Image
#include "File_Image.h"

void displayReadHeader()
{
    uint8_t result;
    myScreen.setOrientation(myOrientation);

    myScreen.clear();
    myScreen.gText(4, 4, "Reading the image header back...");
    myScreen.flushFast();
    wait(4);

    // Read from MCU Flash
    myScreen.clear();
    result = myFile.readScreen(Image_File_Image);
    if (result == RESULT_SUCCESS)
    {
        myScreen.flush();
    wait(4);
    }
}