After about 8 hours of work, I get GPS strings to a TFT display without crashing. But what next? Are there any good libraries to do the math and string parsing.
Try TinyGPS or TinyGPS++.
TinyGPS++ is easy to use and reliable.
No need to do any string parsing, the library does all that for you.
OK. I will try those two libraries. Let's see what happens.
Look at their respective examples in the IDE.
I have Mega2560 and I'm using serial3. Have to check that out
Edit: What a surprise, It wasn't difficult. Now, I have to take my Megaboard and GPS for a walk.
If you find you are loosing GPS msgs data, take a look Arduino Serial I/O for the Real World which includes a GPS example and how debugging (or TFT updates) can interfere with the data handling.
If you are using TinyGPS then just skip the parsing stuff in that tutorial.