PICdude wrote:
>       T2CON = 0x04;     // T2ON, prescaler & postscaler = 1:1
>       T2CON = 0x01;     // adjust prescaler
>       PR2 = 0xB4;     // w/pres.1:1, 0xB4 sets 125us scan rate.
>       TMR2IF = 0x00;
>       TMR2IE = 0x01;
>       ...
>
> Is there a reason for the second line?  T2CON is set, then immediately
> changed again?  I figured I'd ask in case there's some errata I missed
> where perhaps the prescaler is supposed to be set to 1:1 while
> switching on T2, etc.  Or maybe this is some C-specific workaround?
> Or am I reading too far into what is really a typo?

Microchip makes great chips, but their code generally sucks.  Unless the
data or errata documents say something about changing the prescaler from 1:1
only after the timer is on (and I'd be rather surprised if they do), then
this is just a stupidity.

The comments also don't tell you as much as they should.  When you write
this, you should document every bit.  You should never set a collection of
individual bits to a HEX number like this.  Do something like this (from
16F876, may be different on your chip):

  T2CON = 0b00010101;
          //X------- unused
          //-0010--- postscaler 1:3
          //-----1-- timer on
          //------01 prescaler 1:4

Now we can see that the second line actually turns the timer off in addition
to changing the prescaler.  I think it's pretty clear this code is just bad.
Run away.  You're better off writing your own than looking at this bugware.


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