rumpelteazer666 wrote:
> nothing yet. I substituted TRISB=255; with TRISB=1; (setting as input only 
> the last bit), and put a 220ohm resistor between PORTB0 and ground. The i 
> use a clip to connect the 5V to PORTB0 and it plays, i disconnect the clip 
> and it stops again until i connect it again.
220ohm seems too low to me. 10K is what I use for pull-up/down. Maybe
the switching causes a glitch and resets the PIC?

Make sure your circuit is OK. You should have capacitors next+ to the
supply pins. Tie MCLR to VCC with a 10K resistor or so. Tie unused
pins either high or low (you shouldn't need a resistor since pins are
supposed to startup as inputs and nothing should happen due to a
direct connection, but you might want to use resistors to prevent a
software bug that sets them as outputs from blowing your pins). Also
make sure you are connecting your output properly to your amp. Direct
connection to a low impedance input may not be a good idea, you might
want to try capacitor coupling it to a small speaker which is usually
OK for testing. Wire a standard 8ohm small speaker in series with a
1uF capacitor, from PIC pin to ground.

Also you shouldn't just let the program "hang off" the end, even if
there is an infinite loop. Set something notable there, say set some
other output pin and wait 1 second. Then you can watch for that behaviour.

Add a delay at the beginning of the program. Set all output pins low
by default, then wait and set one of them high. wait and set another
one high and unset the first one. Wait for a button press, once
pressed set both and begin the squarewave loop. That should give you
an idea of what happens by connecting 2 LEDs to the pins (through a 1k
resistor of course.)

Oh, a thought. That is pin RB0/INT. Maybe you've got interrupts
enabled for INT input? That could potentially trigger an interrupt on
either the rising or falling edge and jump to position 0x4 in program
space, quite probably restarting the program (which usually begins at
position 0x5 with a jump at 0x0 or so). Setting INTCON=0 should kill
all interrupts

Another thing:

> _asm
> movlw _a
> movwf _d1
> Delay_0:
> decfsz _d1, f
> goto Delay_0
> nop
> nop
>
> _endasm;

That seems wrong to me. I haven't worked with C compilers but _a
should be a *register* or RAM location, NOT a literal value. So not
"movlw _a", but "movf _a,w". I think. You can also just use a constant
with movlw, but I'm guessing you would want to vary the frequency in
the future using 'a'.

I think something is quickly resetting the PIC, and instead of the
delay frequency you are really experiencing startup delays (since your
delay function looks nonfunctional due to the aforementioned detail)
which produce the output squarewave.

Greets,
-- 
Hector Martin (hector@marcansoft.com)
Public Key: http://www.marcansoft.com/hector.asc

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