printf() to a function - can somebody 'splain to me?

[Dale Botkin]

OK, I see you can use printf(fname, cstring, values) to send a formatted string to a function. Does this call the function once for each character, passing that character as a parameter, or what? That's the only way I can think of that it would make sense, but the docs seem to be very vague on this.
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This message was ported from CCS's old forum
Original Post ID: 1355

[John Goss]

Yes, fname is the name of the function fname(). fname() would be a function that does some routine with one char (1byte).
The typical application may be a routine to send one data byte to a LCD. The printf() function takes care of the recursive funtion calls to your fname() function.

void PutCharLCD(char Alpha)
{
code to send 'Alpha' to LCD
}

main()
{
byte voltage = 12;

printf(PutCharLCD,"This is a test.");

printf(PutCharLCD,"Voltage = \%u",voltage);

}




:=OK, I see you can use printf(fname, cstring, values) to send a formatted string to a function. Does this call the function once for each character, passing that character as a parameter, or what? That's the only way I can think of that it would make sense, but the docs seem to be very vague on this.
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This message was ported from CCS's old forum
Original Post ID: 1362

[Dale Botkin]

:=Yes, fname is the name of the function fname(). fname() would be a function that does some routine with one char (1byte).

Thanks, that's what I thought. After posting I re-read the function description in the help file and found the magic cookie crumb... the help file says if you don't specify fname, it defaults to putc(). Since putc() takes a char parameter, I guess that'd mean printf() calls it once for each character to be printed. Thanks for the confirmation!

Dale
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This message was ported from CCS's old forum
Original Post ID: 1375

[kender]

[Ttelmah]

Not surprising really. A _lot_ of the 'library functions', are really '#define' macro operations, rather than true 'functions'. It is a pity that this is not better documented, but it has been reported here in other threads before, where people have trouble using them like this...

Best Wishes

[dbotkin]

Interesting. I go looking for another answer, find one of my own REALLY OLD threads, and notice it's been recently resurrected. :)

OK... now does anyone have a way to pass a variable fname to printf() - OR call printf() either with or without an fname? I have a pretty big function that currently does a bunch of printfs to a function. I need to replicate that functionality with everything being sent to a serial port. I'd rather re-use the existing code, and either use printf() with no fname, or with a different fname depending on where the output needs to go.

Clear as mud? Anyone got a solution? I know I can use an if/else to select one of two printf() calls to use, but that will burn a whole lot more code space.

[frequentguest]

How about having a global flag indicating which device to output to and only have two printf() statements in your fname() function instead of two printf() statements in every place that you need an output?

[kender]

[PCM programmer]

CCS doesn't compile a run-time module for the printf() function.
The printf line is parsed at compile time and only the needed code is
compiled into the HEX file. For example, you can't have a variable format
string in CCS. There is no run-time module to interpret it. The reason:
PICs traditionally (16F-series) have a limited program space.

[dbotkin]