single-wire half-duplex serial to separate Tx/Rx

Projects Networking, Protocols, and Devices
1

I'm trying to connect a TTL serial adapter to an ATtiny85 using a single wire. I figure someone else probably came up with a solution for this. I did find the following post, but it didn't work:
http://forum.arduino.cc/index.php?topic=22664.0
I also tried it with a 2.2K pullup on the Rx, and also tried with the pullup on COM, but the transmission from Tx was always picked up on the Rx.

Anyone have a simple circuit that will work?

2

I spent the afternoon working on it, and came up with a circuit that uses a diode, resistor, and transistor. I also finished writing the receive portion of my tiny serial code, and made it so it will work using two separate pins for Tx and Rx or one shared pin.