> -----Original Message-----
> From: Tom Messenger [SMTP:krist@THEGRID.NET]
> Sent: Tuesday, March 11, 2003 2:37 AM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Re: [PIC]: Voltage to bytes conversion
>
> Didn't the original question mention needing an a/d converter? As opposed
> to just running a comparator?
>
> I thought the need was to digitize inputs that happen to be in the zero to
> half volt range.
>
> I have already deleted the original posting so could be off base here.
> Often am!
> Tom M.
>
>
No mention was made of the requirement for an A/D converter.  The original
post was:

Laura wrote:
"I am a student studying broadcast engineering, and for my final project I
need to use a PIC16C84 to convert multiple small voltage inputs into bytes,
so that the output can be connected to a pc via the com port. Any help with
the code or circuit diagrams for this would be be fantastic. Thank you for
your help."

It sounds to me as though the requirement is only to know if the the input
voltage is either high or low.  This is well within the capabilities of a
16x84, but some external components will be needed to level shift the 0-0.5v
to the pic's logic levels.  Two quad comparators would get the job done.
However, I have to agree with the general consensus that using a
newer/larger device such as the 16F877 would make life considerably simpler.
With the on board A/D and USART, the code would be trivial.

Laura, there is some more information that would be helpfull:
1) What is the source impedance of the 0-0.5volts, i.e. how much current can
be drawn from these signals?  Could you tell us where the signal originate
from?
2) Do you want the PIC to continuously send out a stream of bytes indicating
the state of these signals, or would you want to command the PIC to send out
a byte, either via a serial command or a hardware switch?  If it
continuously sends, do you have any requirements for the rate at which the
data is sent, e.g. as fast as possible, or once per second etc.
3) What bit rate do you require for your serial interface?

Irrespective, this sounds like a pretty simple project.  If you can get the
hardware working then the code will not be difficult.

Regards

Mike



=======================================================================
This e-mail is intended for the person it is addressed to only. The
information contained in it may be confidential and/or protected by
law. If you are not the intended recipient of this message, you must
not make any use of this information, or copy or show it to any
person. Please contact us immediately to tell us that you have
received this e-mail, and return the original to us. Any use,
forwarding, printing or copying of this message is strictly prohibited.
No part of this message can be considered a request for goods or
services.
=======================================================================
Any questions about Bookham's E-Mail service should be directed to postmaster@bookham.com.

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email listserv@mitvma.mit.edu with SET PICList DIGEST in the body