Hardware:

• teensy 4.1 + ethernet connector
• GPS module with PPS on pin 35, GPS TX (pin 0), GPS RX (pin 1) (I'm using a ublox Neo-7N, but many others would work)

Software:

• put https://github.com/ddrown/teensy41_ethernet in your Arduino libraries folder

For the GPS module, you just need PPS, serial output at 115200, and ZDA NMEA messages enabled. If you need a different GPS serial speed or need to use the RMC NMEA message, see the settings.h file.

For tests, see the test/ directory. It uses the ArduinoFake mock environment, which uses the FakeIt mock system and Unity unit tests.

For NTP+GPS status, go to http://[ip]

It will start generating a graph of the local Clock Offset, the local Clock Sync parameters, the Satellite Signal strength, and a "radar" view of the GPS satellites overhead.

IPv4 only:

Memory Usage on Teensy 4.1:
  FLASH: code:82364, data:17116, headers:9060   free for files:8017924
   RAM1: variables:86368, code:79688, padding:18616   free for local variables:339616
   RAM2: variables:12384  free for malloc/new:511904

IPv4+IPv6:

Memory Usage on Teensy 4.1:
  FLASH: code:99836, data:17116, headers:8996   free for files:8000516
   RAM1: variables:90176, code:97160, padding:1144   free for local variables:335808
   RAM2: variables:12384  free for malloc/new:511904