Including Arbitrary Binary Data in Embedded Applications

Posted on One min read

When creating firmware programs for microcontrollers, I regularly need to include to small files such as fonts, bitmaps, or lookup data. The best way I found to do this is to embed the data directly in the binary file.

GCC Assemblers .incbin Directive

First, you create an assembler file (.S) that defines the symbols and references the data.

.section .rodata

.global sysfont_12_font; sysfont_12_font = .; .incbin "roboto-thin-12.mbf";
.global sysfont_16_font; sysfont_16_font = .; .incbin "roboto-thin-16.mbf";
.global sysfont_20_font; sysfont_20_font = .; .incbin "roboto-light-20.mbf";

Declaring the Header File

Then to access the data in C (or C++), you define a header file like the following.

#ifndef ASSETS_H_
#define ASSETS_H_

#if defined __cplusplus
extern "C" {
#endif

extern int sysfont_12_font;
extern int sysfont_16_font;
extern int sysfont_20_font;

#if defined __cplusplus
}
#endif

#endif /* ASSETS_H_ */

Accessing the Data

Finally, you can access the data in a source file as shown in the following example.

#include "assets.h"

int main(int argc, char * argv[]){
    //assign a pointer to the .S binary data
    my_font_t * my_font = (my_font_t*)&sysfont_12_font;

    return 0;
}