SoftwareSerialWithHalfDuplex (formerly SoftwareSerial) - 
Multi-instance software serial with half duplex library for Arduino/Wiring

By default the library works the same as the SoftwareSerial library, 
but by adding a couple of additional arguments it can be configured for 
half-duplex. In that case, the transmit pin is set by default to an input, 
with the pull-up set. When transmitting, the pin temporarily switches to 
an output until the byte is sent, then flips back to input. When a module 
is receiving it should not be able to transmit, and vice-versa. 
This library probably won't work as is if you need inverted-logic.

This is a first draft of the library and test programs. It appears to work, 
but has only been tested on a limited basis. The library also works with 
Robotis Bioloid AX-12 motors. Seems fairly reliable up to 57600 baud. 
As with all serial neither error checking, nor addressing are implemented, 
so it is likely that you will need to do this yourself. Also, you can make 
use of other protocols such as i2c. I am looking for any feedback, advice 
and help at this stage. Changes from SoftwareSerial have been noted with a 
comment of "//NS" for your review. Only a few were required.
Contact me at [email protected], or on the arduino forum.

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA