PIC USART even parity

[vojinilic]

To bas rijetko zatreba, ali ipak zatreba... Datum na ovom fajlu, koji iskopah sa svog diska, je iz 2004. god.
Ovo je najbrzi nacin za brojanje bitova, a kad se izbroje, samo treba setovati taj parity bit, na osnovu rezultata tog brojanja, tj. njegovog bita 0,  i sve radi uredno... Imate slanje sa 9 bita i setovanim parity bitom.

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#include <pic.h>

/*

Freely distributable in this original form.
Any questions or comments?  shane@keyghost.com
Updates to FAQ available from http://www.keyghost.com/htpic

Bit counter by Ratko Tomic, modified for PIC micro by Shane Tolmie
*/

unsigned char bit_count(unsigned int x)
{
unsigned char n=0;
/*
** The loop will execute once for each bit of x set, this is in average
** twice as fast as the shift/test method.
*/
if (x) do
n++;
while (0!=(x=x & (x-1)));
return (n);
}

unsigned int n;
unsigned char c;

void main(void)
{

n=0;
while (n<0xFFFE)
{
n++; //put a break point here and watch c and n!
printf("n=%d, c=%c\n", n, c);
c=bit_count(n);

}
}
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Ima i ova fora sa makroom. Ne znam da li je brze, ali jeste elegantno resenje:

#define PARITY(b) ((((((b)^(((b)<<4)|((b)>>4)))+0x41)|0x7C)+2)&0x80)