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I have a little Parallax GPS module which uses 3 pins, 5vDC, gnd and a bidirectional serial IO pin.

What would be the easiest way to connect the SIO pin to a serial port given that it is bidirectional?

I prefer to use a proper serial port as the SIO pin expects 4800/8/1/n, but I'm not sure how to split the SIO line so that it connects to T1out and R1in without the T1out data being feed back into R1in.

Hints/Tips appreciated.

The protocol used is Parallax’s AppMod serial protocol.

Here are two links to more info:
http://www.parallax.com/dl/docs/cols/nv ... /nv144.pdf

http://forums.parallax.com/forums/defau ... 5&m=258522

Its also labeled the "open serial" scheme.

I didn't look harder for the actual protocol specs, but it sounds similar to I2C but using asynchronous clocking so there's no actual clock pin. The line floats high and can be pulled low by either end.

There should be more info on the parallax web site.

Daryl

This should help.

http://forums.parallax.com/forums/attach.aspx?a=12825