How to reset the GPS receiver?

Hi,

I'm developing a GPS-related application, and I need to use the raw interface.
Sometimes the GPS receiver seems to go nuts: it keeps sending NMEA data
(including 10-12 visible sattelites), but it is unable to find a location.
However, when I start some commercial GPS application, it quickly finds a
valid location.

The question is: is it possible / neccessary to somehow reset the GPS
receiver? If so, how?

Thanks,
BalintN

Henryk
Tue Mar 04 11:32:24 CST 2008

BigB <BigB@discussions.microsoft.com> wrote:

>Hi,
>
>I'm developing a GPS-related application, and I need to use the raw interface.
>Sometimes the GPS receiver seems to go nuts: it keeps sending NMEA data
>(including 10-12 visible sattelites), but it is unable to find a location.
>However, when I start some commercial GPS application, it quickly finds a
>valid location.
>
>The question is: is it possible / neccessary to somehow reset the GPS
>receiver? If so, how?
>

How do you know it is not able to find location? How are you decoding
NMEA? "Visible satellites" are not necessarily "used satellites" it is
the latter that determine if you get a fix and fix quality. I do not
know of any need to reset GPS, but then my GPS sources are usually
(but not always) external units. GPS will send data stream even if the
data are not valid fixes. Check for letters A (valid) or V (invalid)
in RMC sentence or number of satellites in GGA sentence. Several
applications I've seen, ignore these markers and just report erroneous
location (it may be right if it is the last remembered one).

Cheers,
Henryk Birecki

---
Tue Mar 04 14:06:39 CST 2008

On Tue, 4 Mar 2008 04:22:00 -0800, =?Utf-8?B?QmlnQg==?=
<BigB@discussions.microsoft.com> wrote:

>...However, when I start some commercial GPS application, it quickly finds a
>valid location...

Commercial GPS receivers normally keep track of the last position they were at
when powered down. Then when they are powered up, they begin their search
assuming they are still in the same place. It speeds up the search
considerably. If you powered down an aircraft-grade GPS in California and
shipped it to New York and powered it up, it would take a lot longer to lock on
the GPS network because of the gross position shift.


Robert Scott
Ypsilanti, Michigan

PaulC
Tue Mar 04 19:56:08 CST 2008

I had a similar problem except the data (NMEA) coming in was empty - i.e
nothing betwen the commas. But when I stopped using my software and reverted
to built-in software it gave a good fix. I decided I wasn't getting a good
enough initial fix in my software but the built-in software obviously had a
built-in stored advantage. An external antenna in a better, more open
position seemed to make a big difference although I need to work on MY
software to speed things up and maybe hold a position for a restart.
Paul C
"BigB" wrote:

> Hi,
>
> I'm developing a GPS-related application, and I need to use the raw interface.
> Sometimes the GPS receiver seems to go nuts: it keeps sending NMEA data
> (including 10-12 visible sattelites), but it is unable to find a location.
> However, when I start some commercial GPS application, it quickly finds a
> valid location.
>
> The question is: is it possible / neccessary to somehow reset the GPS
> receiver? If so, how?
>
> Thanks,
> BalintN

BigB
Wed Mar 05 04:09:01 CST 2008

Thanks Paul, Henryk, Robert.

It seems we share the same experience. When I said "unable to find a valid
location", I meant that the GPGGA snetences contained no latitude and
longitude values, i.e. I had (mostly) nothing between the commas.

In the end, my receiver found a location - after 6-10 minutes (Robert was
correct).

So, let's change the question a bit: is it possible to tell the GPS receiver
my assumed location, so that it finds a valid fix more quickly?

Thanks,
Balint

"Paul C." wrote:

> I had a similar problem except the data (NMEA) coming in was empty - i.e
> nothing betwen the commas. But when I stopped using my software and reverted
> to built-in software it gave a good fix. I decided I wasn't getting a good
> enough initial fix in my software but the built-in software obviously had a
> built-in stored advantage. An external antenna in a better, more open
> position seemed to make a big difference although I need to work on MY
> software to speed things up and maybe hold a position for a restart.
> Paul C
> "BigB" wrote:
>
> > Hi,
> >
> > I'm developing a GPS-related application, and I need to use the raw interface.
> > Sometimes the GPS receiver seems to go nuts: it keeps sending NMEA data
> > (including 10-12 visible sattelites), but it is unable to find a location.
> > However, when I start some commercial GPS application, it quickly finds a
> > valid location.
> >
> > The question is: is it possible / neccessary to somehow reset the GPS
> > receiver? If so, how?
> >
> > Thanks,
> > BalintN

Henryk
Wed Mar 05 11:20:55 CST 2008

BigB <BigB@discussions.microsoft.com> wrote:

>Thanks Paul, Henryk, Robert.
>
>It seems we share the same experience. When I said "unable to find a valid
>location", I meant that the GPGGA snetences contained no latitude and
>longitude values, i.e. I had (mostly) nothing between the commas.
>
>In the end, my receiver found a location - after 6-10 minutes (Robert was
>correct).
>
>So, let's change the question a bit: is it possible to tell the GPS receiver
>my assumed location, so that it finds a valid fix more quickly?

Yes, (at least approximately - "In California") on most commercial
external units through user setup interface or even through data port
if you know protocol. You'd need to ask whoever makes an embedded
device what access and protocol there is to send data to it. Most
manufacturers specify "cold start" time. 6-10 minutes seems way
excessive unless reception is really poor. You should always test GPS
outside.

Cheers,
Henryk

BigB
Wed Mar 12 06:25:01 CDT 2008

All right, this is THE question.
What protocols, what commands are there? Does NMEA support it? Or SIRF?
Regards,
BigB

"Henryk Birecki" wrote:

> BigB <BigB@discussions.microsoft.com> wrote:
>
> >Thanks Paul, Henryk, Robert.
> >
> >It seems we share the same experience. When I said "unable to find a valid
> >location", I meant that the GPGGA snetences contained no latitude and
> >longitude values, i.e. I had (mostly) nothing between the commas.
> >
> >In the end, my receiver found a location - after 6-10 minutes (Robert was
> >correct).
> >
> >So, let's change the question a bit: is it possible to tell the GPS receiver
> >my assumed location, so that it finds a valid fix more quickly?
>
> Yes, (at least approximately - "In California") on most commercial
> external units through user setup interface or even through data port
> if you know protocol. You'd need to ask whoever makes an embedded
> device what access and protocol there is to send data to it. Most
> manufacturers specify "cold start" time. 6-10 minutes seems way
> excessive unless reception is really poor. You should always test GPS
> outside.
>
> Cheers,
> Henryk
>

NeilH
Wed Mar 12 06:32:54 CDT 2008

This will depend on what gps receiver is fitted.
You need to tell us which model you are using as different receivers have
different initialise methods.


"BigB" <BigB@discussions.microsoft.com> wrote in message
news:01B98369-AC90-4D6D-AA1C-DC2E6EC4CD2B@microsoft.com...
> All right, this is THE question.
> What protocols, what commands are there? Does NMEA support it? Or SIRF?
> Regards,
> BigB
>
> "Henryk Birecki" wrote:
>
> > BigB <BigB@discussions.microsoft.com> wrote:
> >
> > >Thanks Paul, Henryk, Robert.
> > >
> > >It seems we share the same experience. When I said "unable to find a
valid
> > >location", I meant that the GPGGA snetences contained no latitude and
> > >longitude values, i.e. I had (mostly) nothing between the commas.
> > >
> > >In the end, my receiver found a location - after 6-10 minutes (Robert
was
> > >correct).
> > >
> > >So, let's change the question a bit: is it possible to tell the GPS
receiver
> > >my assumed location, so that it finds a valid fix more quickly?
> >
> > Yes, (at least approximately - "In California") on most commercial
> > external units through user setup interface or even through data port
> > if you know protocol. You'd need to ask whoever makes an embedded
> > device what access and protocol there is to send data to it. Most
> > manufacturers specify "cold start" time. 6-10 minutes seems way
> > excessive unless reception is really poor. You should always test GPS
> > outside.
> >
> > Cheers,
> > Henryk
> >

BigB
Wed Mar 12 17:01:01 CDT 2008

Hi Neil,

I have two devices:
- ASUS P526
- Mitac Mio A201

Both have built-in GPS receivers, both emit NMEA (I have no specs on what
version they use/understand), both claim they are SIRFStar III compatible.

However, my application should run on the possible widest range of devices,
so I'd like to find the most general way to set the GPS.

Thanks,
BigB

"NeilH" wrote:

> This will depend on what gps receiver is fitted.
> You need to tell us which model you are using as different receivers have
> different initialise methods.
>
>
> "BigB" <BigB@discussions.microsoft.com> wrote in message
> news:01B98369-AC90-4D6D-AA1C-DC2E6EC4CD2B@microsoft.com...
> > All right, this is THE question.
> > What protocols, what commands are there? Does NMEA support it? Or SIRF?
> > Regards,
> > BigB
> >
> > "Henryk Birecki" wrote:
> >
> > > BigB <BigB@discussions.microsoft.com> wrote:
> > >
> > > >Thanks Paul, Henryk, Robert.
> > > >
> > > >It seems we share the same experience. When I said "unable to find a
> valid
> > > >location", I meant that the GPGGA snetences contained no latitude and
> > > >longitude values, i.e. I had (mostly) nothing between the commas.
> > > >
> > > >In the end, my receiver found a location - after 6-10 minutes (Robert
> was
> > > >correct).
> > > >
> > > >So, let's change the question a bit: is it possible to tell the GPS
> receiver
> > > >my assumed location, so that it finds a valid fix more quickly?
> > >
> > > Yes, (at least approximately - "In California") on most commercial
> > > external units through user setup interface or even through data port
> > > if you know protocol. You'd need to ask whoever makes an embedded
> > > device what access and protocol there is to send data to it. Most
> > > manufacturers specify "cold start" time. 6-10 minutes seems way
> > > excessive unless reception is really poor. You should always test GPS
> > > outside.
> > >
> > > Cheers,
> > > Henryk
> > >
>
>
>

PaulC
Tue Apr 29 20:34:00 CDT 2008

Google for "Sirf" & "protocol" and you should find a download. That's what I
did quite a while ago. Sirf themselves are no help at all unless you have
bought a product directly from them. anything incorporated in another product
and they don't want to know. If you get the download it tells you how to
communicate with the GPS. I did, so it can't be hard, but it was a couple of
years ago and I have forgotten it all + have a new computer so don't have the
file anymore. It's out there, I assure you

"BigB" wrote:

> Hi,
>
> I'm developing a GPS-related application, and I need to use the raw interface.
> Sometimes the GPS receiver seems to go nuts: it keeps sending NMEA data
> (including 10-12 visible sattelites), but it is unable to find a location.
> However, when I start some commercial GPS application, it quickly finds a
> valid location.
>
> The question is: is it possible / neccessary to somehow reset the GPS
> receiver? If so, how?
>
> Thanks,
> BalintN

BigB
Mon May 05 12:19:16 CDT 2008

Thanks, I found the (not yet complete) solution based on your guidance.

For anyone interested: the initialization can be done with SIRF messages. I
did not find the specific message however, only an API call
(SirfInitializeReceiverEx) in a 3rd party toolset (see
http://www.linkspoint.com/toolkithelp/SirfInitializeReceiverEx@GPSINITMODE@const_PGPSINITTIME@const_PGPSPOSITION@const_BOOL@const_BOOL.html) for details.

I cancelled implementing it however, because I don't want to switch to and
from NMEA and SIRF protocols.

Thanks anyway,
Balint

"Paul C." wrote:

> Google for "Sirf" & "protocol" and you should find a download. That's what I
> did quite a while ago. Sirf themselves are no help at all unless you have
> bought a product directly from them. anything incorporated in another product
> and they don't want to know. If you get the download it tells you how to
> communicate with the GPS. I did, so it can't be hard, but it was a couple of
> years ago and I have forgotten it all + have a new computer so don't have the
> file anymore. It's out there, I assure you
>
> "BigB" wrote:
>
> > Hi,
> >
> > I'm developing a GPS-related application, and I need to use the raw interface.
> > Sometimes the GPS receiver seems to go nuts: it keeps sending NMEA data
> > (including 10-12 visible sattelites), but it is unable to find a location.
> > However, when I start some commercial GPS application, it quickly finds a
> > valid location.
> >
> > The question is: is it possible / neccessary to somehow reset the GPS
> > receiver? If so, how?
> >
> > Thanks,
> > BalintN

Henryk
Mon May 05 14:31:24 CDT 2008

See:
http://gpsd.berlios.de/vendor-docs/sirf/sirf_binary.pdf

Henryk Birecki

BigB <BigB@discussions.microsoft.com> wrote:

>Thanks, I found the (not yet complete) solution based on your guidance.
>
>For anyone interested: the initialization can be done with SIRF messages. I
>did not find the specific message however, only an API call
>(SirfInitializeReceiverEx) in a 3rd party toolset (see
>http://www.linkspoint.com/toolkithelp/SirfInitializeReceiverEx@GPSINITMODE@const_PGPSINITTIME@const_PGPSPOSITION@const_BOOL@const_BOOL.html) for details.
>
>I cancelled implementing it however, because I don't want to switch to and
>from NMEA and SIRF protocols.
>
>Thanks anyway,
>Balint
>
>"Paul C." wrote:
>
>> Google for "Sirf" & "protocol" and you should find a download. That's what I
>> did quite a while ago. Sirf themselves are no help at all unless you have
>> bought a product directly from them. anything incorporated in another product
>> and they don't want to know. If you get the download it tells you how to
>> communicate with the GPS. I did, so it can't be hard, but it was a couple of
>> years ago and I have forgotten it all + have a new computer so don't have the
>> file anymore. It's out there, I assure you
>>
>> "BigB" wrote:
>>
>> > Hi,
>> >
>> > I'm developing a GPS-related application, and I need to use the raw interface.
>> > Sometimes the GPS receiver seems to go nuts: it keeps sending NMEA data
>> > (including 10-12 visible sattelites), but it is unable to find a location.
>> > However, when I start some commercial GPS application, it quickly finds a
>> > valid location.
>> >
>> > The question is: is it possible / neccessary to somehow reset the GPS
>> > receiver? If so, how?
>> >
>> > Thanks,
>> > BalintN

Henryk
Mon May 05 14:48:54 CDT 2008

OOPS... I forgot the one you may be more interested in

http://www.remember.ro/dl/nmea0183.pdf

look for $PSRF100

Henryk Birecki





Henryk Birecki <soaringpilot@sbcglobal.net> wrote:

>See:
>http://gpsd.berlios.de/vendor-docs/sirf/sirf_binary.pdf
>
>Henryk Birecki
>
>BigB <BigB@discussions.microsoft.com> wrote:
>
>>Thanks, I found the (not yet complete) solution based on your guidance.
>>
>>For anyone interested: the initialization can be done with SIRF messages. I
>>did not find the specific message however, only an API call
>>(SirfInitializeReceiverEx) in a 3rd party toolset (see
>>http://www.linkspoint.com/toolkithelp/SirfInitializeReceiverEx@GPSINITMODE@const_PGPSINITTIME@const_PGPSPOSITION@const_BOOL@const_BOOL.html) for details.
>>
>>I cancelled implementing it however, because I don't want to switch to and
>>from NMEA and SIRF protocols.
>>
>>Thanks anyway,
>>Balint
>>
>>"Paul C." wrote:
>>
>>> Google for "Sirf" & "protocol" and you should find a download. That's what I
>>> did quite a while ago. Sirf themselves are no help at all unless you have
>>> bought a product directly from them. anything incorporated in another product
>>> and they don't want to know. If you get the download it tells you how to
>>> communicate with the GPS. I did, so it can't be hard, but it was a couple of
>>> years ago and I have forgotten it all + have a new computer so don't have the
>>> file anymore. It's out there, I assure you
>>>
>>> "BigB" wrote:
>>>
>>> > Hi,
>>> >
>>> > I'm developing a GPS-related application, and I need to use the raw interface.
>>> > Sometimes the GPS receiver seems to go nuts: it keeps sending NMEA data
>>> > (including 10-12 visible sattelites), but it is unable to find a location.
>>> > However, when I start some commercial GPS application, it quickly finds a
>>> > valid location.
>>> >
>>> > The question is: is it possible / neccessary to somehow reset the GPS
>>> > receiver? If so, how?
>>> >
>>> > Thanks,
>>> > BalintN