> > But instead of using a header on a PCB that might be optimised for
> > size, what I thought would work is, in the tracks coming away from
> > 10F, have breaks between closely-adjacent pads and after the s/w
> > has been uploaded, close the gaps with a solder bridges. And to
> > get the programme into the micro, either temporarily solder a 5-way
> > connector during development or, to re-programme in the field, de-
> > solder the bridges, push spring-loaded pins onto the pads to upload,
> > then re-solder the bridges
>

> Olin's programmer (the professional one, not so sure about the
> EasyProg) is capable of dealing with some not very nice ICSP
> conditions. Perhaps if you just design carefully you could use a
> programmer like that and avoid the hassle of desoldering/resoldering
> bridges.
>
> Josh

You can get a programmer (like http://www.embedinc.com/proprog) that is more
capable of overpowering the target circuit than many other programmers, but
you still have to consider what that does to the rest of the circuit.  I've
done several 10F designs, and dealing with in circuit programming has each
time been the most complicated issue.

Since 3 of the 4 I/O pins will be envolved in ICSP, you have to think about
this carefully.  Particularly keep in mind that GP3 (MCLR) will be rasied to
13V during programming.  This means it can't be driven directly by a logic
gate during normal operation.  The knee jerk answer is to put 20Kohms in
series with whatever is driving GP3, but also note that the internal weak
pullup is always enabled when this pin is used in the MCLR role.  In one
case it worked out conveniently for this to be an open collector line using
the weak MCLR internal pullup.  The drivers were all special chips or
discrete transistors that could handle 13V when off.  Other times, I just
couldn't use the MCLR function so that the weak pullup could be off.  Note
that this also prevents using the weak pullups on other the other pins GP0
and GP1.

The 10Fs are great small and "simple" parts, but I've found require
disproportionally more thought and care to use effectively than bigger PICs.
And yes, this sometimes means adding a few resistors and the like to the
circuit that are only useful during programming.  That may add a couple
cents to the overall cost, but it's still impressive what you can do for 1/3
dollar.  Also keep in mind the total cost of producing a unit with a
programmed 10F.  $.05 in extra parts is bound to be cheaper than production
tech time messing around with solder bridges, not to mention the
reliability.


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