Why not have have the PGM pin use a one pin connector that can be very  
basic.
Could even be finger trace on the edge of the PCB.  A cable with a  
dual tine fork could
slip over the finger.
What does the housing look like ?  Anyplace a small hole could allow  
access to the
PCB ?  Maybe next to the USB connector.
Gus

>
> On Feb 10, 2010, at 7:31 PM, Johansson wrote:
>
> Dear piclist,
>
> I am developing a USB product. For different logistics reasons, I'd  
> like to
> program the PIC18F13K50 in-circuit, after the housing is assembled.  
> To do
> that, I could add a special ICSP connector, but to keep costs low  
> and the
> housing neat, I'd like to have the existing USB connector double as  
> the ICSP
> connector, if possible. However, as "Single-Supply In Circuit  
> Programming"
> (formerly known as Low-Voltage ICSP programming) needs 5 pins, the  
> USB plug
> is one pin short. So my idea was to use the USB shield as the PGM pin.
> According to the USB spec, the shield should not be connected  
> anyway. Of
> course, the ICSP adapter used to program the firmware into my  
> device, would
> have to be custom made, and even violate the USB standard. But what  
> do you
> guys think, would it work? During normal execution, is it a problem  
> that the
> shield is connected to the PGM pin?
>
> Summary of connections:
> PIC VPP - not needed for ss-ICSP
> PIC VDD - wired to VBUS of USB plug
> PIC GND - wired to GND of USB plug
> PIC PGD - wired to D+ of USB plug
> PIC PGC - wired to D- of USB plug
> PIC PGM - wire to SHEILD of USB plug
>
> I have submitted this question to Microchip support, but they  
> responded by
> asking me what ss-icsp was, and then don't answer any more.
>
> Before you suggest a bootloader; there are security considerations  
> for this
> product, which means no bootloader can be used.
>
>
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist