Allow SoftwareSerial to share RX and TX pins. [imported]

[cmaglie]

This is Issue 1022 moved from a Google Code project.
Added by 2012-08-30T14:00:13.000Z by [email protected].
Please review that bug for more context and additional comments, but update this bug.

Original labels: Type-Enhancement, Priority-Medium, Component-SoftwareSerial

Original description

What change would like to see?

From Ed Baafi. The ability for SoftwareSerial to use the same pin for RX and TX (half-duplex). See: https://github.com/Modkit/Arduino/commits/new-extension for a possible implementation.

It would be good if this worked well / simply if you only wanted to either transmit or receive, but not both.

Why?

To reduce pin usage.

Would this cause any incompatibilities with previous versions? If so, how
can these be mitigated?

[sbrynen]

I've submitted a pull request to allow passing SOFTWARESERIAL_UNUSED for a pin you don't want to use to allow TX only or RX only