> Now the problems... With the visual tests for the LED segments, the 
> operator
> has to watch the LED's carefully.  It takes no more than a minute to run 
> the
> full sequence, but it adds up to a bunch of time when 500+ of these are
> assembled.  And if I do run the self-test on a full panel of 10 at once, I
> would need to slow down the test-display sequence so the operator can see 
> it.
> What I'm wondering is if there is some way to have the PIC check itself 
> for
> shorts/opens.  Shorts should be simple -- the code can toggle the RB3 
> output
> for example, and check RB2 and RB4 to ensure that they don't follow RB3. 
> But
> checking for shorts at other points on the board (where pins are not
> necessarily adjacent to each other, but may run to PCB traces very close 
> to
> each other) may be tedious.  Is there any clever way to check for opens? 
> Is
> there any clever way to check if the LED's actually light up (by checking
> their voltage drop), but keeping in mind that I don't have any spare 
> I/O's.

Since you already plan to bring your analog inputs out to a test jig, 
perhaps you could add circuitry to the test jig to allow the PIC to measure 
the supply current to its own board using those inputs. Then you could not 
only determine if an LED lights, but also if more than one does!

Bob Ammerman
RAm Systems


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