Ok - I think you are both correct - connecting up my DMM I get the
expected results ... (although not quite as visually as i would like)
- derivatives huh, interesting and I understand what you are saying
but for now I'll put it down to silly me and my interpretations of
visual data translated into text, like you said you really have to be
here...
I think I need to go to scope school
... I am using a Phillips PM3050 here and have never had the manual or
any instruction, just sort of picking up bits of enlightened 'oh! ok
thats what that does' here and there ...
Its has two probes which was helpful as I could look at the input to
the TX XBee and the output of the RX XBee and see what was happening
to the pulse (a slight phase shift in case you're interested which can
be easily accounted for in the mechanical side of the wotsit I'm
building) ...
So when the ground potentials of both trace's are equal I get good
scopin results - TX or RX gnd - by using the RX ground I could then
confirm what the DMM had done already anyhoo...
When using the two separate ground potentials for both traces the TX
trace that was using a benchtop power supply gave an ok scope (same
gnd as the AC for the scope hmmm) yet the battery powered one went
screwy ... Yet using the battery ground on both traces gave ok
results on both traces (likewise both on the TX/benchtop as already
discussed).
There is likely some sort of lesson to be learned from this ?
I often jump into things a little fast and then get caught up on
relatively simple 'problems' that in reality is just the gear doing as
it should ...
Thanks as always for being my online tutors ! I hope I'm not taking advantage
in case anyone is interested:
http://www.maxstream.net/blog/2007/07/03/filming-dog-races/
Really need to get them going with serial transmission proper and not
this line-passing business - still got to learn to crawl beforehand...
cheers!
nick
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