>>
        The devices that will communicate, will nearly be in contact with
each
other, and there will be no
external light interference at all.
        The reason to use infrared communication, is because both will be
sealed
boxes, and there can=B4t be
a connector due to possible corrosion of metals.
        The speed should be 9600 or 19200 bauds.
        Any better solution (cheaper and safer) than an irda chipset ?
<<

In that case just drive the transmitting LED from the UART output inverte=
d.
In other words, the LED is on when the UART output pin is low, off when
high.  This is because the idle state is high.  Use an appropriate
phototransistor or photodiode in the receiver.  A small analog circuit
detects the on/off states of the light beam and drives the UART input pin.
Again, the pin must be driven low when the light is on.  Make sure the
circuit has enough gain to detect the worst case lowest detected light
level - but not much more.  There will generally be a tradeoff between ga=
in
and speed.  19200 baud with the transmitter and receiver nearly touching
should be no problem.  I don't think you'll need more than one or two
transistors and a few resistors.

I've done this sort of thing with IR being sent about 6 inches inside a
hollow shaft from a stationary board to a rotating board.  Works great.


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(978) 742-9014, http://www.embedinc.com

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