Colin Constant wrote:
> Granted.  But let me ask this:  if we limit the discussion (for the moment)
> to 5-pin polarized headers for ICSP, what is the agreed pinout?

My reaction is "why does it matter?"

Another way of addressing your question is to ask

        What use are you going to make of the ICSP facility?

Your answer to this question will shape the set of useful
answers to the first question.  I can think of several types
of answer:

A) I will be making thousands of production boards that will
    require field firmware upgrades several times a year.

B) This is a contract design that will go into 1 million furby
    dolls   Once shipped, it will never be touched by anyone over
    the age of 4.

C) I am making both a generic trainer board AND a programmer
    board to go with it for my university class.  I expect all
    my users to have access to both units.

D) I want to buy/make a dozen trainer boards, one from Wouter,
    one from Jan, one from Olin, one from ...  etc, and I would
    like to use a single serial<->icsp programmer for all of them.

E) I want to be able to buy a single programmer and use it with
    any development board out there.

F) I'm a beginner, I don't know where to start, and this
    plethora of choices confuses me.

Problem sets A,B, and C all call for you to make your own
decision based on cost, support issues and personal
preferences.  D and E are probably what you were thinking
about when you posted, but are "uninteresting".  That is,
if a board *has* an ICSP connector that is documented, it
is a trivial task to build a 1-off adapter harness to
connect it to whatever programmer one is using.  If "F"
is your game, then you are probably best off in buying a
complete development environment from someone (Microchip,
CCS, Jan, Wouter, Olin...) that includes both a dev board and
a ICSP programmer.  In any case, once you have mastered
the basics of a particular development board, it is but a
short step to building a custom prototype board (either on
a breadboard or using a PCB house) - at which point one
can design in whatever ICSP/ICD connector one desires.

To illustrate the many design choices in this seemingly
simple area, consider the following:

I prefer RJ12-modular connectors for ICSP, except that one
of my projects connects to a model-train control bus that
also uses that connector; what happens in the field if
someone misplugs the wires?  Molex 0.1x5 is great, but
suffer from connector reversal issues.  Using a keyed "x6"
solves that problem, but I *hate* crimping molex
connectors!  Adding another pin to support ICD makes it
even nicer, but production boards, by definition, don't
need ICD :-)  Back to my model train board, the users of
this board will NOT have a serial programmer board (i.e.,
standard ICSP is useless for them), so I will need to
design in an alternative for them based around a
DB15/MAX232 and client software that toggles a PC's serial
port control pins.  Of course, cost matters, and ICSP
headers and connectors can add $1-$2 to the cost of
manufacturing - a consideration that doesn't matter if
one is building a 1-off development board for their own
use.

To violently agree with Olin, I'm only one person on the
list, and I've got a need for several different ICSP
pinouts/connectors; multiply me times the number of
developers out there and I'd be mildly astonished if there
were *only* a couple of hundred alternatives :-)

All told, the question really is really a mix of
        what problem do you need to solve,
        how much are you willing to spend solving it, and
        how long will it be a problem?

   -John

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