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I have an FMB900 - on Firmware 03.25.15.Rev.32 - the On Stop Settings are:

  • Min Period = 3600
  • Min Saved Records = 1
  • Send Period = 120

Deep Sleep is enabled with a Timeout = 15 (mins).

The device appears to "wake up every hour" and send data to the server.

On the Server, I see the following:

  • Satellites = 0
  • GPS\GNSS Status = 3
  • Altitude = 0

I get the impression that when the unit comes out of Deep Sleep to send the data packet as per Min Period (On Stop) of 3600s, the GPS isn't actually being used. Or by the time the GPS gets a fix (hot\warm start) the data packet has already been sent.

In System settings under Records Savings/Sending Without TS - the value is set to After Position Fix.

On Moving - I see values for Satellites, Altitude and GPS\GNSS Status = 1. 

In I/O - GNS Status: Priority = Low and Operand = Monitoring. 

Can anyone shed any light or explain how the On Stop works in terms of the GPS, i.e. does the unit wait up every Min Period, get a fix and then send the data packet? Or does it wake up and just send a data packet (without fix)? I am seeing the 2nd version (i.e. wake up & sends packet with no GPS fix).

I've gone through the logs on the server and the behaviour was there before as well.


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You can read about how deep sleep mode works here:

There are few condition for device to enter sleep mode if those conditions are met device enters deep sleep mode that is why you get following "GPS\GNSS Status = 3" It means GNSS sleep. Because your settings are "Records Savings/Sending Without TS - the value is set to After Position Fix", FMB920 time is synchronized with GNSS satellites and GPS fix is obtained before GNSS module goes to sleep. GSM/GPRS module gets turned off and every data sending period it gets turned on to send a packet, but if all conditions for deep sleep mode are still present, GNSS module does not come out of a sleep mode it is in, it means no new GPS data is being received, that is why you get 0 satellites, as for device to remain in deep sleep mode it has to be stationary (On stop), because if ignition and movement is detected it comes out of deep sleep mode and GNSS module wakes up. That is why when you are using vehicle (Moving) you get GPS\GNSS Status = 1 which is GNSS ON with fix and you see satellite count and other information as GNSS module is no longer sleeping and is capturing new data.

So when device is in deep sleep mode and sends records every configured time interval it does not actually mean that it comes out of a deep sleep mode it always remain in deep sleep mode as long as conditions are true and On Stop acquisition settings really do not interfere with GPS data, these settings define how often new record is captured, how many are captured and how often they are sent to a server.

In deep sleep mode power is being saved as GNSS module is sleeping and no new GPS data is being recorded as there is no purpose because vehicle will remain in deep sleep mode as long as it is not moving so GPS data does not really change at this point.

If you have any questions, please ask.

Best Regards
Best answer


Thank you for the explanation. 

I also found another question\answer - which sheds some more light on the sleep behaviour. In essence, if no movement is detected - then the On Stop packets appear to effectively be "heartbeat" packets.

Many Thanks