Some issues to solve in the Modbus Master-Slave library

Slave issues

The Slave side has been adopted from a previous work. It just enhances it to include several new features like:

• Functions 1, 2, 5 and 15.

It also needs some improvements with the register handling. Maybe simplify it.

Master issues

The Master side works quite good when testing it with two arduinos, one as a Master and the other one as an Slave. Anyway, there are still some issues:

• Master needs to implement function codes 1, 2 and 15.
• There is no flag to show "watch-dog time-out". This is important when there is no answer from any slave.

Serial port issues

• Arduino HardwareSerial now includes support for other frames aside 8N1, such as 7E1, 7E2 or 8O1.