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Pixmap file on SD-card

The portable pixmap file on SD-card library saves the screen as a portable pixmap file on the SD-card and loads a portable pixmap file into the frame-buffer, ready to be displayed. Everything is performed dynamically at run-time. It is much faster than BMP, as it reads and writes the frame-buffer directly.

Info

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

The portable pixmap file on SD-card library is available on the Commercial edition. The file is PBM coded.

Configure

Warning

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

#include "hV_File_P4.h"

The pre-processor statement includes the file library.

Danger

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

Ensure the external SD library is installed and properly configured.

File_P4 myFile(&myScreen);

The constructor File_P4() sets the link to the screen.

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bool 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(1);
}

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.

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.

beginFileSystem() returns RESULT_SUCCESS if successful, RESULT_ERROR otherwise.

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

uint8_t pinCardCS = myScreen.getBoardPins().cardCS;
bool result = myFile.beginFileSystem(pinCardCS);
Legacy version 5

beginFileSystem() returned a boolean value, now replaced by clear constants.

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.

Use

Save

myFile.saveScreen("File_P4");

saveScreen() saves the screen on the SD-card as a portable pixmap file. The file is PBM coded.

The required parameter is

  • The first line provides the name of the file without the .P4 extension.

Read

myFile.readScreen("File_P4");

readScreen() displays a portable pixmap file from the SD-card on the frame-buffer, to be displayed with flush().

The required parameter is

  • The first line provides the name of the file without the .P4 extension.

The function checks the size or the multiplier of the image.

End

myFile.endFileSystem();

endFileSystem() closes the SD-card.

Example

This is the core of the code from example File_P4.ino.

void fileWriteReadP4()
{
    // Initialise
    bool 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 P4");
    myScreen.flushFast();

    // Write to SD-card
    myFileP4.saveScreen("File_P4");
    wait(4);

    myScreen.clear();
    myScreen.gText(4, 4, "Reading the file back...");
    myScreen.flush();
    wait(4);

    // Read from SD-card
    myScreen.clear();
    myFile.readScreen("File_P4");
    myScreen.flush();
}