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rust-raspberrypi-OS-tutorials/0A_pcscreenfont
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bzt ed7cb505f9 Fixed typos and more tutorials 7 years ago
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Makefile Initial commit 7 years ago
OLVASSEL.md Fixed typos and more tutorials 7 years ago
README.md Fixed typos and more tutorials 7 years ago
delays.c Initial commit 7 years ago
delays.h Initial commit 7 years ago
font.psf Initial commit 7 years ago
gpio.h Initial commit 7 years ago
kernel8.img Initial commit 7 years ago
lfb.c Initial commit 7 years ago
lfb.h Initial commit 7 years ago
link.ld Initial commit 7 years ago
main.c Initial commit 7 years ago
mbox.c Initial commit 7 years ago
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README.md

Tutorial 0A - PC Screen Font

Drawing pixmaps is fun, but definitely there's a need to display characters as well. Basicaly fonts are nothing more than bitmaps for each character. For this tutorial I choosed PC Screen Font format, the same Linux Console uses.

Lfb.h, lfb.c

lfb_init() sets up resolution, depth, and color channel order. Also queries framebuffer's address.

lfb_print(x,y,s) displays a string on screen.

Font.psf

The font file. Use any file from /usr/share/kbd/consolefonts. Unicode table is not supported. Translating characters to glyph index using that table (instead of one-to-one relation) is a homework for you. This font is generated from the original IBM PC VGA 8x16 Font ROM, and includes 127 glyphs.

Makefile

I've added a new object file, generated from the psf. It's a good example of how to include and reference a binary file in C. I've used the following command to find out the label:

$ aarch64-elf-readelf -s font.o
        ... output removed for clearity ...
     2: 0000000000000820     0 NOTYPE  GLOBAL DEFAULT    1 _binary_font_psf_end
     3: 0000000000000000     0 NOTYPE  GLOBAL DEFAULT    1 _binary_font_psf_start
     4: 0000000000000820     0 NOTYPE  GLOBAL DEFAULT  ABS _binary_font_psf_size

Main

Very simple. We set the resolution and display the string.