Hello, Wouter,

As said, the hardware is already sitting here, 1000 pcbs, soldered, no
chance to change anything. Three weeks earlier and I would have made it
different, but now... For it's a SMD pcb it should be no big deal to make
that short. Not professional, I know, but if it works reliable....

Internal pull ups: That's what first came into my mind, but RB5 has no
internal pull up.

Specs of port pins: I know there are figures in the data sheet saying 25mA
max. but I also read of applications driving LEDs e.g. without any current
limiting resistor, so I thought of the possibility of some sort of internal
limitation. But I don't know.

Peter




> I got a project ready to go into serial production and now my customer 
> stepped up with an additional idea. He likes to have different 
> features with
> 2 differerent models, but hardware unchanged.
> It would be possible to load differerent software by ICSP, but I had 
> another idea this morning:

Configuration jumpers are a tried and tested idea. There are even special
PCB shapes (solder jumper) that are designed to accept a little blob of
solder to make a sort. I'd suggest you use those instead of shorting two
normal islands.

As for your method of reading the pin: outputting a 0 on a pin connected to
+5v is definitely beyond the specs of a PIC. How long it will survive and
how it will fail is anyone's guess. Probably no problem for a child's pet,
but a definitive no-no for a nuclear power plant.

How about using the internal pull-ups? Or use a 3-wire solder jumper? Or
solder a small (1k ?) resistor (a 1206 SMD would probably fitt well) instead
of the short?

-- 

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: www.voti.nl consultancy, development,
PICmicro products docent Hogeschool van Utrecht: www.voti.nl/hvu

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