[Ovmsdev] How to get a quick and reliable GPS fix
christopher.cook at webprofusion.com
Wed Nov 5 13:13:03 HKT 2014
I don't know much about this myself but I do know my TomTom satnav (not
GPRS enabled) requires a regular QuickGPSFix update downloaded to keep
it up to date with expected satellites. SatNav's without that update
have to rely on historical information about the satellites instead.
On 05/11/2014 00:42, Arthur Hebert wrote:
> 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 reset.
> 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.
> OvmsDev mailing list
> OvmsDev at lists.teslaclub.hk
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