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'[PIC]: Odd problem....'
2003\02\23@203635 by Jonnathan Partamian

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part 1 502 bytes content-type:Text/Plain; (decoded quoted-printable)

When I turn on my circuit board (it is very simple, and I'm used to PIC...)
my PIC simply don't works, as if it was without a crystal. Then, if I
connect the GND of the osciloscope to the board (and it is not grounded!)
the PIC start to run perfectly...

What may be happening?



God bless you all,



Jonnathan Partamian

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part 3 2 bytes
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2003\02\23@205353 by Herbert Graf

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> When I turn on my circuit board (it is very simple, and I'm used
> to PIC...)
> my PIC simply don't works, as if it was without a crystal. Then, if I
> connect the GND of the osciloscope to the board (and it is not grounded!)
> the PIC start to run perfectly... What may be happening?  God
> bless you all,  Jonnathan Partamian

       Well there are a few questions. First which PIC, what crystal speed? How
have you set the configuration bits? How do you know the PIC isn't running?
I'm sure there will be more questions but these come to mind first. Of hand
guess? You forgot the caps connecting each of the crystal leads to ground,
or your caps are the wrong size. TTYL

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2003\02\23@222004 by Ian McLean

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This problem has surfaced a few times recently on the list - and the
solution is usually the same.

Checklist for you...

1) Check your configuration bits.  In my experience though, this is usually
not the problem, but the following are ...
2) Check that MCLR is tied HIGH.
3) Are you declaring any port as input, or leaving any pin defaulted to
input, and leaving the pin floating ?  This is a common problem with ICSP
when those port B pins are not used for anything else (should in this case
be tied LOW when not in use).
4) Check that the XTAL caps are correctly sized and tied to earth.  They
should be ceramic type.  Check that your crystal and caps are as close to
your PIC as possible.
5) Is the crystal you are using within spec. ?  The caps need to be sized to
fit the crystal you are using (check datasheet).


These are all possible problems that could lead to the behaviour you are
witnessing.

RGs
Ian.

{Original Message removed}

2003\02\24@001739 by cdb

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On Mon, 24 Feb 2003 14:19:12 +1100, Ian McLean wrote:
Checklist for you...

Also check the watchdog time is disabled in the config fuses

colin

1) Check your configuration bits.  In my experience though, this is
usually
not the problem, but the following are ...
2) Check that MCLR is tied HIGH.
3) Are you declaring any port as input, or leaving any pin defaulted
to
input, and leaving the pin floating ?  This is a common problem with
ICSP
when those port B pins are not used for anything else (should in this
case
be tied LOW when not in use).
4) Check that the XTAL caps are correctly sized and tied to earth.
They
should be ceramic type.  Check that your crystal and caps are as
close to
your PIC as possible.
5) Is the crystal you are using within spec. ?  The caps need to be
sized to
fit the crystal you are using (check datasheet).


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2003\02\24@063327 by Ian McLean

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Are you using only 1 x 22pF ceramic ?  Sounds like it from your reply.  You
should be using two - one leg of each capacitor to each of the two pins on
the XTAL, the other side of both caps tied together and to earth.

If you have 1 cap tied between the two legs of the XTAL, this is probably
your problem ...

Rgs
Ian


{Original Message removed}

2003\02\24@072354 by Olin Lathrop

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> From: "Jonnathan Partamian" <jonnathanfpspamKILLspamIG.COM.BR>
> To: <.....PICLISTKILLspamspam.....MITVMA.MIT.EDU>
> Sent: Sunday, February 23, 2003 8:25 PM
> Subject: [PIC]: Odd problem....

Please put the text of your message in the email body where it belongs and
refrain from using attachments unless necessary.


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Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

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2003\02\24@181152 by Russell McMahon

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Jonnathan

I see you've only started posting to the list recently - welcome to the
club! :-)

I see you've had answers to your original "odd problem" question so I don't
need to add more.

I see that in your posts so far you have no text in the message body and
instead attach the message in a separate file. I don't know what email
program you are using - maybe this is the only way you can send messages?
But, if at all possible, you would be much better off placing the text in
the body of the message. That way people who skim down the large number of
incoming messages can see at a glance what your subject is and decide
whether they are able to help. When the text is in an attachment many people
will not open it to see what it says. You posted a reply to the
"Differential Amplifiers" thread - this was good and useful comment and it's
a shame that people might miss it when it's in an attachment.

Also, the title "Odd problem ..." does not give people any idea at all of
the subject - you are much more likely to attract expert advice if you give
a brief summary of the problem in the subject line.

Finally :-),  you (or probably your email program) have attached a small gif
file to each message. This doesn't seem  to contain any useful information
and takes up extra bandwidth. For many people this is not a problem but some
list members have limited bandwidth and receiving "useless" attachments
annoys them.

Hope this is helpful. Welcome to the PICList!




               Russell McMahon

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