Unused pins should be set to output. And to save current, should be
driven low. Another thing to check might be the IC sockets (if used). If
they are super cheap, they may be causing problems.

Josh
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Lindsay Pallickal wrote:
>
>     I've assembled a circuit on a homebrew PCB, it's a datalogger that
> outputs data via the USART. The problem is that when I tap or vibrate the
> board I get errors in the serial stream. I first suspected loose connections
> so I soldered the connectors in place. Well, the errors were reduced but not
> eliminated. Any ideas what on could be the root of the problem? Btw, the PIC
> and serial port grounds are connected. Also I do have a number of unused PIC
> pins that are left ungrounded. Would that be an issue? If so, should I set
> the unused pins as inputs or outputs to minimize problems?

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