[Ovmsdev] How to get a quick and reliable GPS fix

Arthur Hebert ahebert at gmail.com
Wed Nov 5 00:42:36 HKT 2014

Hi All,

Does anyone know the details of how, most reliably and most quickly, to get
a location fix from the GPS module after it has been powered up and after
it has come out of sleep mode?

I have written my own code using the OVMS hardware. To save power, it turns
off the GPS power (AT+CGPSPWR=0) and puts the module to sleep (AT+CSCLK=2)
while the vehicle is parked (i.e. no CAN bus activity). Once there is CAN
activity again, it comes out of sleep mode (AT+CSCLK=0) and turns on the
GPS (AT+CGSPPWR=1). Immediately after turning on the GPS power, I also
issue one of the GPS reset commands (AT+CGPSRS=0 or AT+CGPSRST=1).

The module documentation if vague about when to use the 0 reset or the 1

I know that the GPS module itself isn't made to function while the module
is asleep even though the commands may not give an error.

I've read that it takes up to 15 minutes to get a fix on most GPS devices.
In practice, sometimes I get a fix within a minute every time I start up,
and other times I don't get a fix even after hours of trying with either
reset option.

Any information will be greatly appreciated.

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