question about the ili9341 stm32f4 spi driver

[franksterb92]

in the tm_stm32f4_ili9341.c file the function putc in the for loop that draws the font data there is a if statement that shifts b by j and compares that with 0x8000 why is that value there why is it 0x8000 and not something else

for (i = 0; i < font->FontHeight; i++) {
    b = font->data[(c - 32) * font->FontHeight + i];
    for (j = 0; j < font->FontWidth; j++) {
        if ((b << j) & 0x8000) {
            TM_ILI9341_DrawPixel(ILI9341_x + j, (ILI9341_y + i), foreground);
        }
    }
}

[MaJerle]

Fonts are described as a fixed size array, for instance variable TM_Font7x10 has 10 uint16_t array values per character.
Each character line is described as bitfield where font is "active" and where we should draw background.

If we draw from left to right, we want to check always bits from left to right. This is done by shifting our uint16_t value by j and then check MSB bit. Mask for MSB bit is 0x8000.

[franksterb92]

cool that makes since now thanks for writing all these drivers I've learned so much just looking through these