Portable pixmap PBM binary file¶

The portable pixmap PBM binary file 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.

The portable pixmap PBM binary file 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 portable pixmap binary 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. 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_P4 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.

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

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

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¶

Save¶

uint8_t result = myFilemyFile.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.

The function returns RESULT_SUCCESS if successful, RESULT_ERROR otherwise.

Read¶

uint8_t result = myFile.readScreen("File_P4");

readScreen() loads 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.

The function returns RESULT_SUCCESS if successful, RESULT_ERROR otherwise.

Terminate¶

uint8_t result = myFile.endFileSystem();

endFileSystem() closes the SD-card.

The function returns RESULT_SUCCESS if successful, RESULT_ERROR otherwise.

Example¶

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

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

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

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

    // Read from SD-card
    myScreen.clear();
    result = myFile.readScreen("File_P4");
    if (result == RESULT_SUCCESS)
    {
        myScreen.flush();
    wait(4);
    }
}