NeoICSerial - AltSoftSerial replacement with attachInterrupt

In the same category as NeoHWSerial, I have modified PaulS's excellent AltSoftSerial library to support interrupt-driven character processing. As stated in the previous thread, I have seen occasional questions about handling received characters with interrupts, and many GPS users have been stymied by serial libraries only providing polled reading/events

I started with the source code for AltSerial and made the minimal modifications to implement an attachInterrupt method, identical to the pre-existing [

attachInterrupt

](https://www.arduino.cc/en/Reference/AttachInterrupt) for digital Pin Change interrupts. Whenever a character is received, it calls the registered procedure from the ISR:

static void handleRxChar( uint8_t c )
{
  gps.decode( c );
}

void setup()
{
  serial_port.attachInterrupt( handleRxChar );
  serial_port.begin( 9600 );
}

I have also updated the NeoGPS example to use this class to handle GPS characters as they are received.

Cheers, /dev