Maybe first just try to turn led on or off.  See what led does when you 
don't turn it on or off, then try to get  it to change state.  Once you get 
it where one program turns it on and another program turns it off, you can 
try to get it to flash.

If somethng don't work, simplify it till it does then work your way back 
up..

Bill


----- Original Message ----- 
From: "William Chops Westfield" <westfw@mac.com>
To: "Microcontroller discussion list - Public." <piclist@mit.edu>
Sent: Friday, March 10, 2006 5:57 PM
Subject: Re: [PIC]


>
> On Mar 10, 2006, at 11:51 AM, pic wrote:
>
>> My C program for flashing leds is not working.
>>       /* Light the LEDs */
>>       LATD += 1;
>>
>
> Both of your programs use this to 'toggle' the LEDs, but
> I'm not sure it's  a good idea due to the usual
> problems with Read/Modify/write on PICs.  Just because you
> wrote a 1 or 0 to a port pin doesn't mean that's what will
> be read back when you read the port...
>
> Try it with a shadow register...
> latd_shadow += 1;
>     LATD = latd_shadow;
>
>> void delay (void)
>> {
>>   for (i = 0; i < 10000; i++)
>>     ;
>> }
>>
> Depending on compiler specifics, this might be a very short
> delay to pair to human perceptions.  I have a "flame" simulator
> that changes the brightness of some LEDs with a 128 count inner
> PWM loop and a 50 count outer loop (so, approximately equivilent
> to a 6400 count single loop) that flickers at a reasonably
> realistic rate (several times per second, at least), and it has
> a lot more stuff in the inner loop than your code.  I seem to
> recall that PICs at nominal frequency take 24 bits worth of
> count to get delays in the one-second range.  (Hmm.  That was
> implicit in your timer-based attempt.  prescale of 32 on a a
> 16 bit counter is ~2million cycles per second.)  I would hope
> your compiler does the delay loop in far less than 100 cycles,
> for a delay period of far less than 0.5 seconds...
>
> BillW
>
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