I had a lot of trouble getting other GPS examples to work. So I took Edoardo De Marchi's code from 2014 and hacked it until it was working on newer hardware.

Advice:

• Start with confirming the module works in U-Center, and know the baud rate. Many older libraries assume 9600. Newer modules run at higher baud rates
• Use a good terminal program and confirm you have human readable messages starting with "$GNGGA" or "$GPGSV" or similar.

Comments in code include links to NMEA sentence guides:

• http://navspark.mybigcommerce.com/content/NMEA_Format_v0.1.pdf
• https://www.gpsinformation.org/dale/nmea.htm#nmea

Most libraries do not include sentence filters for the types of sentences output by my M8N (and perhaps other modules as well)

Most older versions of the MODSERIAL library do not update properly to support STM32. I have found and included a version of the lib which will compile without errors. However, when using it in my code, the NMEA sentence gets corrupted somehow (for example showing some HUGE [6 digit] Satellite count, etc.