In an SIM808 chip or similar you can get the GPS information with this AT command:
the UTC time is in the third data field as: yyyyMMddhhmmss.sss
However in the manual the function of
AT+CGNSSEQ is described as: Define the last NMEA sentence that parsed.
My question is in general:
- how accurate is this time when I receive it from the serial interface of the chip?
- Should I assume that the time between the AT command answer and the last NMEA message that was received by the GPS unit is variable?
- Can I compensate for delays in the systems and how?
Delays I expect:
Difference between NMEA sentence coming in and AT command?
Time to process NMEA sentence
Time to read AT command and prepare response
Serial communication time