Improve Serial Port Functionality

[bfranske]

Right now this library only works with UART1. There are two enhancements which would be needed to support additional features. First, allow UART 0 to be used as an option instead of UART 1. This would allow transmit and receive capability to be added to the code. UART1 is Tx only while UART 0 is Tx and Rx.

Second, allow the use of software UART interfaces. See https://github.com/plieningerweb/esp8266-software-uart for software UART code. This would allow more than one universe of DMX transmit and receive on a single ESP8266 chip. This allows for further applications such as multi-universe sACN (E1.31) nodes, DMX combiners and splitters, etc. This has already been done on the AVR Arduino's see http://www.deskontrol.net/blog/arduino-four-universes-dmx-512-library/ for an example of that.

[negis02]

Hi. i not have posibility to use UART1, because in my ESP PCB GPIO2 is hard vired directly to VCC.
Do it is easy way to modify code for to use UART0?

thank