Hi Josh, coincidentally I'm currently ... doing rotary encoder stuff=20
with XC8.  :)

A few comments.

I found that having a filter circuit between the encoder and PIC pins is=20
essential.  Unlike pushbuttons, I was not able to both "debounce" the=20
encoder and have react nicely to user input in software.  I'm using=20
Bourns PEC09 series, and the datasheet gives a filter circuit that works=20
nicely.

I don't have acceleration yet but that is next up.

The algorithm I'm using is to sample (i.e. not interrupt on encoder=20
output changes) at 1Khz, I need a timer ISR at the rate for other things=20
anyway, and in that ISR I do the quadrature checking and check for=20
press, and report that to the main loop doing the UI.

I have 2 encoders and it is simple enough for me to just replicate code.=20
  Since it is in an ISR it needs to be efficient, but not critically so.

If I wanted to make this flexible and extensible, I'd probably do=20
something like having one general-purpose encoder handling function=20
("ProcessEncoder"), and pass to it the state of the A&B&press, and a=20
pointer to a variable/structure for it to output its computation to (or=20
just have the function return a 8/16-bit value indicating whatever).  So=20
this way that encoder handler doesn't know or care what PIC pins are used.

If the encoder function needs initialization or configuration, such as=20
telling it the range of what its output should be (i.e. 0-100, or 0-5,=20
etc.) that could be in the struct.  So the struct could be something like..=
..
{
bool doInit;
uint8_t minVal;
uint8_t maxVal;
uint8_t currVal;	// encoder computes
uint8_t buttonPressed;	// encoder computes
uint8_t encState;	// encoder internal state info
}

So to setup the encoder, the main code would do this:
doInit=3D true;
minVal=3D 0;
maxVal=3D 100;

and call ProcessEncoder().  ProcessEncoder() would see that doInit is=20
true and then do whatever housekeeping is necessary (and set doInit to=20
false).

Subsequently, in a timer or mainloop or in response to interrupts on the=20
PIC pins the encoder is wired to, you'd read the PIC pins, and do:=20
ProcessEncoder( A,B,button, &encoder1struct );

So now you have a general-purpose encoder library routine that can be=20
used with multiple encoders and called different ways (main loop, ISR,=20
....) depending on the design.

There are a bunch of variations on this theme but as other posters have=20
said it is the beginning of OOP and code reuse.  Also as other posters=20
have said it is awkward to impossible to pass to a function the pin to=20
use; I handle that by having the caller of the function read the pins=20
necessary (and possibly set output pins in response to what the function=20
says to do.)  A small amount of hard-coding but it is fast.

Anyway, my extended 2c
J





Josh Koffman wrote:
> Hi all,
>
> So as you may have guessed, I'm working on some rotary encoder routines i=
n XC8.
>
> I've been looking around, and I've actually found a pretty neat
> Arduino library. It handles the encoder, acceleration (values change
> faster if you spin faster), encoder switch status (click, double
> click, held, etc). I'm considering trying to port it to XC8 as I think
> it would be useful, but also a really good exercise in coding.
>
> I have no Arduino experience, but from what I've been reading, it
> appears that in their ecosystem you can define multiple instances of a
> class. So in my case if I made one routine that dealt with a single
> encoder, I could create 2 instances to deal with 2 encoders, etc. As
> far as I understand it, I can't do that in straight C.
>
> So, what is the preferred way of dealing with this? I could make the
> original function deal with total number of encoders that I have. Or I
> could make multiple copies of a function that dealt with a single
> encoder. In both cases I'll need to deal with variables carefully.
>
> Is there another (possibly better) way? I'm interested in this in the
> abstract as eventually I will likely run into this situation with
> other routines (switch debounce, for instance).
>
> Thanks!
>
> Josh
>
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