FX30S 16.10.1.m3 WP85 GNSS time to first fix issues

#1

Hi

  • WP8548 FX30S
  • The system has no IP network connection (SMS only)
  • The FX30S RTC is reset following POR (no battery is fitted to the FX30s)
  • A SIM was fitted during testing - the system time is correct at the start of testing - I think this is because it’s being set by cellular network time
  • I noticed that if I leave the SIM out the system time is not set even if the GNSS has time - I haven’t checked the impact on TTFF

I have noticed that in order to acheive fast time to first fix (TTFF) I need to issue a command line “poweroff” to the modem.

  1. Is this because “poweroff” triggers long term storage of the alamanac and / or ephemeris? or something else?

  2. Is there another way to trigger this other than “poweroff” ?

  3. Is documentation available for this behaviour and how to acheive good TTFF performance with the FX30S?

Some test results

After power on reset
TTFF start = 812 s

After "gnss restart cold"
TTFF start = 183 sec
TTFF start = 256 sec

After gnss fix and reboot from command line (no POR)
TTFF start = 11 sec

Following "poweroff" command and power cycle
TTFF start = 34 sec
TTFF start = 10 sec

Following "poweroff" command and after 24 hours powered down  
TTFF start = 39 sec 

John