I think i found the problem. I didn't realize i had to put a capacitor betw=
een Vusb and Vss, even if i didn't use USB.


> From: jack.monegato@hotmail.it
> To: piclist@mit.edu
> Subject: [PIC]PIC18F2550A, Pwm doesn't work when using on external power =
supply
> Date: Mon, 26 Sep 2011 18:57:02 +0200
>=20
>=20
> Hello there,
> I have quite a big problem. I am building a sound synthesizer using a 18F=
2550 as tri/sqr wave generator. Wrote the program, tested on breadboard, tr=
ansfered to board, tested on board (with PICkit 2)... everything just PERFE=
CT.
>=20
> I also built a 12 to 9 to 5 V power supply by putting in series a 7809 th=
en a 7805, it works, the voltages are what they should be (9V is for the an=
alog part of the circuit), I can hear the square wave but not the triangula=
r (from PWM output). PWM seems not to work. but if i touch to some random a=
nd unconnected parts (i.e., the sixth pin in the programmer dock) I can hea=
r, at lower than expected frequency, another square wave, from the pwm outp=
ut. Then if i unplug the external supply and plug in the PICkit i have to t=
urn on then turn off then turn on and ONLY after that the pic start working=
 properly again.
>=20
> Unfortunately i don't have any measurement tool but a multimeter and a st=
einberg sound card (as sound analyzer). The voltmeter dysplays 4.62V when w=
ith PICkit and 5.02V when power supply
>=20
> Any suggestion? I already changed a couple of capacitors in the supply ci=
ruit, but nothing changed. the circuit is:
>=20
>                        ______           |->+9V       ______
> 12VDC --+------+------| 7809 |---+------+-----+-----| 7805 |---+------+--=
--> +5V
>         |      |      |______|   |      |      |    |______|   |      |
>         =3D 100uF=3D 0.1uF    |      =3D 0.1uF=3D 100uF=3D0.1uF   |      =
=3D 0.1uF=3D 47uF
>         | 40V  |          |      |      | 40V  |        |      |      | 1=
0V
> 0V    --+------+----------+------+------+------+--------+------+------+--=
--> GND
>  		 	   		 =20
> --=20
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 		 	   		 =20
--=20
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