I've set up two XBee pro units to do digital line passing - so the pin
states are mirrored between the remote TX unit and the base RX unit..
In setting up the units I had them on the same power supply and ground
potential and had them working fine passing a %50 cycle 25Hz digital
pulse (3.3v) between themselves - Well, the purpose of having wireless
is so you don't have to use the same power and ground potential isn't
it...
So I set the RX unit up on its own battery power supply and sent it on
its merry way to the other end of the desk all by its lonesome ... Now
on the scope its giving a sine-ish wave output on its output pin (the
mirrored one) at about 20Hz-ish when idle and when I send my 25Hz
pulse its the same 20Hz-ish wave with little spikes where there should
be a digital transition from high to low or vice-versa ...
However ... this glitch disappears if I connect the units to the same
ground potential.
If I connect the two grounds by a 10MOhm resistor I get a kind of
'half-problem' where I get my digital pulse at 25Hz but modulated by
the 20Hz-or-so pulse ...
What am i doing wrong ? I have used the XBee's for line passing
successfully beforehand - no idea where this glitch is coming from
prob something really beginners ?
nick
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