Updates:

• GPS status via UBX protocol. (lower overhead compared to NEMA 1803)
• NTP client for fail-over on GPS/PPS loss.
• Improved stability of temperature compensation.
• Human-readable status via UDP port 23.

Human readable status examples:

$ echo -n 'ntp' | nc -uW1 -w1 #.#.#.# 23
gps epoch:   0xE7423F96.71E6AA43
ntp offset:  0xFFFFFFEE.00000000
ntp servers: pool.ntp.org
    address          stratum  leap  reach  next  offset (ms)  delay (ms)  jitter (ms)  drift (ppm)  skew (ppm)  weight
  - 38.229.60.9            2     0  77777     8        2.750      29.478        0.328       -0.142       6.376  0.1159
  - 159.89.86.140          2     0  77777     5        7.713      23.209        0.390        0.317       8.137  0.0000
  - 144.172.118.20         2     0  77777    10        0.260       9.997        0.190        0.267       4.714  0.1568
  - 45.79.214.107          2     0  77777     7        2.613       7.500        0.404        1.649       8.263  0.0895
  - 162.159.200.1          3     0  77777     4        0.576      10.040        0.249        0.512       4.612  0.1603
  - 23.131.160.7           2     0  77777    10        5.772      29.849        0.178        0.402       3.595  0.2056
  - 74.6.168.73            2     0  77777     7        3.304      35.071        0.310        0.232       6.270  0.1179
  - 155.248.196.28         2     0  66767     4        0.970      25.825        0.194       -0.397       4.354  0.1540
clock stratum: 1
clock offset: 2.411 ms
clock drift: 0.304 ppm
leap indicator: 0 

$ echo -n 'gpsdo' | nc -uW1 -w1 #.#.#.# 23
pps locked: yes
current offset: -88 ns
mean offset: -17.6 ns
rms offset: 42.9 ns
frequency skew: 0.0215 ppm
frequency correction: -175.9287 ppm
  - pll trimming: 0.0839 ppm
compensation: -176.0126 ppm
  - temperature: 37.834 C
  - bias: 37.230 C
  - coefficient: 0.4296 ppm/C
  - offset: -176.2722 ppm

 Temperature Compensation Settling: