Is there a particular function in the library TinyGPS or TinyGPS Plus which outputs the raw NMEA sentences? I couldn't find anything about it on the website guide of the library.
There doesn't seem to be, but what you could do is print each character as it arrives. From their example code:
while (nss.available())
{
if (gps.encode(nss.read())) // <--- pass to TinyGPS
return true;
}
So, change that to be:
while (nss.available())
{
char c = nss.read(); // <--- get the incoming character
Serial.print (c); // <--- print it
if (gps.encode(c)) // <--- now pass it to TinyGPS
return true;
}