My Oncore docs give a suggested circuit with a 74HC132:
GPS-6_1PPS --+-----------------+ +--- MAX232_T2in
| | |
| 4 +-- |
1 +-- 3 & o--+
| & o-- R=10k --+-- 6
2 +-- 5 |
| +-- C=470p -- +5V
|
9 +-- 8
| & o-- R=820 -- D=PPS LED -- +5V
10 +-- K A
I think that the generated pulse is only about 5 usec and was
doubtful it would work for me over a 15-20m cable run. I've had
regular rs232 work without problem over the same distance in
the past.
I've not started on this yet but will test with a short cable
run first and increase the pulse width as needed.
David
David,
Difficult to read your diagram, even in a fixed spacing font.
My point was that the individual active lines should be paired with ground
lines for transmission.
If the pulse is only 5 microseconds, I would definitely want Chris to see
how mangled (or otherwise) it was at the end of the run he has. It may
well be pushing the limits, especially if it's not using the cables as
twisted pairs. Perhaps your circuit could be modified to produce
something nearer 100 ms by replacing the C with something about 20K times
bigger? A 1 uF or so?
Cheers,
David
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