This source replaces the standard printf() and sprintf() functions in the compiler C library with low resource version with a limited set of features and output types.

Features of miniprintf include:
 • %c character
 • %d,%i signed integer (- sign added if needed)
 • %s character string
 • %u unsigned integer as decimal
 • %x or %X unsigned integer as hexadecimal (uppercase)
 • %% to write %
 • Padding with 0 or space, up to 9 digits
 • #define to allow for additional padding characters ._?
 • #define to allow %f floating point representation up to 2 decimals

Developer must implement: int _fwrite(char *str, int len) to send data out to the correct location

Example implementation of _fwrite:

int _fwrite(const void *buf, size_t count)

{

    char * p = (char*)buf;

    while(*p && count){

        uart1_putchar((uint8_t)*p);

        p++;

        count-=1;

    }

    return 0;

}

We compiled a test program for miniprintf using ARM GCC for STM32, and a few different configurations.

Results with -O0
 • Test code without printf() - 8,800 bytes
 • Test code with standard printf() - 35,072 bytes (+26,272 bytes)
 • Test code with miniprintf() - 10,384 bytes (+1,584)
 • Test code with miniprintf() and float support - 10,704 bytes (+1,904 bytes; +320 bytes vs without float)

Results with -Os
 • Test code without printf() - 4,352 bytes
 • Test code with standard printf() - 32,064 bytes (+27,712 bytes)
 • Test code with miniprintf() - 5,024 bytes (+672 bytes !)
 • Test code with miniprintf() and float support - 6,936 bytes (+2,584 bytes; +1,912 bytes vs without float)