> Remember my weather station project;

No.

> As always I have  questions  about about the 16F877, here are the
questions:
> 1. Can I have wireless transmission of data from the '877 if yes how can
> implement that with RF signals?

You would have to connect the PIC to some external transmitter, perhaps
driven from the UART output.  Keep in mind that any radio link is a noisy
channel.  At best the receiver will get most of the data intact most of the
time.

> 2. Do I need an external oscillator or not, I figure the most favored is
an
> XT.

See section 12.2 on page 123 of the data sheet.  I won't waste everyone
else's time duplicating that information here.

> 3. Since the '877 accepts analog signals do I need ADCs for the pressure,
> humidity and temperature sensors or the built in ones(if there are any)
will
> work.

The built in A/Ds work as long as you can scale your analog signals to cover
most of the 0 to 5V range, the source impedance is no more than 10K ohm, and
about 1 part in 500 accuracy over the full range is sufficient.  Most of
these conditions can probably be met easily if the hardware is designed with
the PIC in mind.


*****************************************************************
Olin Lathrop, embedded systems consultant in Devens Massachusetts
(978) 772-3129, olin@cognivis.com, http://www.cognivis.com

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