Your code aside, if you're looking for speed maybe you should be writing it=
 in assembly? I don't know what kind of optimization your compiler is using=
 so maybe it's a moot point? Are you concerned about counting every transit=
ion or if it's accurate will ever other transition work? When writing encod=
er code I found a number of ways to write it. It was a while ago so I don't=
 remember the source (sorry) but I know it helped me to read about the stra=
tegies before I was coding to see what the payoff was.=20

Best of luck,
Charles, AC0GD

---

This e-mail was sent from my iPhone to provide you my quickest response. Pl=
ease forgive the "corrected" misspellings and brevity of my mobile e-mails.

> On Jan 17, 2014, at 8:59 AM, slippyr4 <slippyr4@gmail.com> wrote:
>=20
> Hi all,
>=20
> I want to count pulses from a rotary encoder who's output is 2 channel gr=
ay
> code. I need to increment a counter when the encoder turns one way, and
> decrement it when it turns the other way.
>=20
> I want to handle the signals as fast as I can (so that I can support the
> highest frequency of signal I can get away with). Numerous models of the
> encoder are available, and the faster I can get the code, the better
> resolution encoder I can use.
>=20
> My test circuit has the two signals connected to RB0 and RB1, and i'm usi=
ng
> the INT0 and INT1 interrupts to detect the signal changes.
>=20
> For now, i'm working in C on a PIC18f252. The final device I'll use i'm n=
ot
> certain of yet but it will probably be one of the newer pic18 devices. Bu=
t
> that's not really very important at this stage.
>=20
> I might consider reworking the code in assembler if there's a significant
> gain to be had, but really at this stage i'm wondering if my *logic *is
> correct, or could be improved.
>=20
> Here's my code so far. Conceptually, are they any optimizations i'm missi=
ng?
>=20
> if (INTCONbits.INT0IF) // INT0 & RB0 are encoder channel A
> {
> // change the edge we fire on
> INTCON2bits.INTEDG0 =3D !PORTBbits.RB0;
> // clear the interrupt
> INTCONbits.INT0IF=3D0;
>=20
> if (PORTBbits.RB0 =3D=3D PORTBbits.RB1)
> {
> count++;
> }
> else
> {
>  count--;
> }
> }
> else  if ( INTCON3bits.INT1IF ) // INT1 & RB1 are encoder channel B
> {
> // change the edge we fire on
> INTCON2bits.INTEDG1 =3D !PORTBbits.RB1;
> // clear the interrupt flag
> INTCON3bits.INT1IF=3D0;
>=20
> if (PORTBbits.RB1 =3D=3D PORTBbits.RB0)
> {
> count--;
> }
> else
> {
> count++;
> }
> }
>=20
> thanks
> slip
> --=20
> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist

--=20
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.