pic - Integer to ASCII in C18

I'm writing code for a PIC18F46K22 using the C18 compiler. I want to write the value of an integer \$n\$ in ASCII over the USART to my PC.

For \$n<10\$, it's easy:

Write1USART(n + 0x30); // 0x30 = '0'

This would work for \$10\le{}n\le100\$:

Write1USART((n/10) + 0x30);
Write1USART((n%10) + 0x30);

But this isn't the fastest possible way, probably.

So is there a built-in function or a function somewhere out there that I could just use instead of rolling my own?

Answer

The C18 compiler supports the number-to-ascii family of standard C functions in stdlib.h: itoa(), ltoa(), ultoa() et cetera.

Depending on which compiler / stdlib.h you have, the relevant function prototype would be:

extern char *   itoa(char * buf, int val, int base); // signed int
extern char *   utoa(char * buf, unsigned val, int base); // unsigned int

or

extern char *   itoa(char * buf, int val); // signed int
extern char *   utoa(char * buf, unsigned val); // unsigned int

If you were looking for a relatively robust built-in "standard" C way for converting your numbers to ASCII strings, these xtoa() functions would be the ones to use.

If on the other hand you are constrained to squeeze a few extra cycles or bytes of memory out of the final code, then several of the other answers to your question are the way to go.