time synchronization without gps
- 2 June 2015 at 11:17 am #735Jason GreenbergGuest
I was wondering if it would be possible to initiate a time synchronization with UTC time without connecting to an external GPS. In other words I would like to send artificial packets from a PC/microcontroller to cause a time-synchronization with the PC/microcontroller’s clock or access to UTC time alternative source.
I work on my experiments in a basement, so I do not have easy access to the GPS signals.
If not, what is suitable GPS product that is compatible the UM7?
Jason4 June 2015 at 12:57 pm #736Caleb ChamberlainMember
You could do that, but it might take some work. The UM7 has a free-running hardware timer with better than microsecond resolution that starts running when it powers on. It uses incoming PPS pulses and GPS packets to perform a second-order calibration on that timer, synchronizing it to GPS time. The PPS pulse is expected to come in at 1 second intervals with very high accuracy, on the second. Once the GP9 receives the PPS pulse, it uses the next GPS RMC packet to extract the time at which the pulse went high.
To synthesize the timing synchronization without GPS, you’d need to have a piece of hardware that outputs a PPS pulse once a second, and that sends a NMEA RMC packet immediately after each pulse so that the UM7 can extract the time.
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