> Would someone please recommend a site that has details
> of a homebrew programmer that is suitable for programming
> PIC18FX52 series controller via ICSP pins (not low
> voltage mode).

It sounds like the EasyProg (http://www.embedinc.com/easyprog) is exactly
what you are asking for.

The only issue may be the rest of the target circuit when doing in-circuit
programming.  The EasyProg is better than most hobby programmers in that
regard, but all in circuit programmers have limitations and put some
requirements on the target circuit.  The EasyProg uses active pull ups and
passive pull downs on Vpp and Vdd with fixed wait times.  This is good
enough in many cases, but won't tolerate large capacitance on Vdd for
example.

The next step up from the EasyProg is the ProProg
(http://www.embedinc.com/proprog).  It is an industrial strength in circuit
programmer that has active low and high drive on Vpp and Vdd, and closed
loop control thru A/Ds to verify the voltage gets to the desired level.
However, at $295 instead of $59 it is probably not what you are looking for.

> It would be particularly helpful if the site explained the protocol
> for talking to the programmer so that I can
> write a VB program to control the hardware. (I understand there are
> probably many free upload programs
> but I want to write my own or modify an existing one so it can be
> customized).

Both of the programmers I mentioned use the same host protocol, which is
fully documented.  Go to the Documentation section near the bottom of either
web page and click on "Protocol specification".  This should be all you need
to write software to drive either programmer from any computer with a
standard serial port.

There are Windows command line programs and a linkable library available for
free download.  The library encapsulates the protocol details and provides a
procedural interface to applications.  The source code for the library and
applications is also available, which might be useful as examples even if
you want to write all your own software.


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