A-GPS (was Re: Freerunner as a mobile gateway -> shipping container)
On 2011-05-24 08:42, Ed Kapitein wrote: You could overcome the TTFF problem by using the agps software from [1] It loads the needed data from the gps chip and uses that the next time you power on the gps unit. I usually get a fix in 2 minutes. Hi Ed, For some reason I thought the Antaris chip in the GTA02 didn't support all of the AID message types but only AID-INI (which provides a basic saved position and time but nothing else like almanac or ephemeris). I think it has something to do with the facts that (a) the chip doesn't send ACK messages in response to any AID-* messages, making it hard to know if the messages you're sending are good, and (b) I've never managed to get a Freerunner to send me a AID-DATA probe which is the message that means "please send me any available aid data". Why my Freerunners never send AID-DATA whereas the code you pointed to clearly expects to receive it I have no idea. In any case, I decided to try again. This time I just send it all the AID messages at startup whether it asks for them or not. The results are good so far. If the Freerunner has network connectivity within a few minutes of startup, I subsequently get fresh AID data from the Internet and send that too. The result is that the GPS gets two copies of the AID data, one saved from the last shutdown and one fresh from the Internet. It doesn't seem to mind. Thanks for motivating me to try this A-GPS stuff again. -Phil ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community
Re: Freerunner as a mobile gateway -> shipping container
[1] https://github.com/gabrys/gta02-agps :-) On 05/24/2011 02:42 PM, Ed Kapitein wrote: > On 05/23/2011 07:24 PM, Phil Vandry wrote: >> On Wed, May 18, 2011 at 03:19:16PM +0200, Eric Smith wrote: >>> Main application here is in a sea shipping container. >>> >>> The key issues are RF communication (when in a GSM range of course) >>> and power management due to the long haul journey including journey >>> overland. Power supply has to be in the form of an additional battery. >>> >>> Technical issue is to have minimal size OS and to be low in power >>> consumption. And robust. >> If you sleep and only wake up at intervals, you should anticipate some >> difficulty acquiring a GPS signal every time you wake up. The GPS in >> the Freerunner is really designed to make use of A-GPS and if you can't >> do it because you are at sea and far from any network signal, it can >> take a long time to get a position. We have sometimes seen it take over >> 40 minutes to get a good fix (unit mounted on an aircraft glareshield). >> >> -Phil >> >> ___ >> Openmoko community mailing list >> community@lists.openmoko.org >> http://lists.openmoko.org/mailman/listinfo/community >> >> > You could overcome the TTFF problem by using the agps software from [1] > It loads the needed data from the gps chip and uses that the next time > you power on the gps unit. > I usually get a fix in 2 minutes. > If you send the log data to a server via GPRS, you might want to use > rsync with the --inplace option. > The logs will only grow i suspect and i use this method of transferring > the gps log from my car to my server at home, > while driving. > It also helps to chop the log files in smaller parts (+/- 2Mb per file) > in case the GPRS connection is not that reliable, a resend > will take less time. > Roaming data can be expensive, so you might want to look at that too, > with your mobile phone provider. > > Good luck with your project, and keep us posted about the > successes/failures, we would like to learn from it. > > Kind regards, > Ed > > > > ___ > Openmoko community mailing list > community@lists.openmoko.org > http://lists.openmoko.org/mailman/listinfo/community > > ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community
Re: Freerunner as a mobile gateway -> shipping container
On 05/23/2011 07:24 PM, Phil Vandry wrote: > On Wed, May 18, 2011 at 03:19:16PM +0200, Eric Smith wrote: >> Main application here is in a sea shipping container. >> >> The key issues are RF communication (when in a GSM range of course) >> and power management due to the long haul journey including journey >> overland. Power supply has to be in the form of an additional battery. >> >> Technical issue is to have minimal size OS and to be low in power >> consumption. And robust. > If you sleep and only wake up at intervals, you should anticipate some > difficulty acquiring a GPS signal every time you wake up. The GPS in > the Freerunner is really designed to make use of A-GPS and if you can't > do it because you are at sea and far from any network signal, it can > take a long time to get a position. We have sometimes seen it take over > 40 minutes to get a good fix (unit mounted on an aircraft glareshield). > > -Phil > > ___ > Openmoko community mailing list > community@lists.openmoko.org > http://lists.openmoko.org/mailman/listinfo/community > > You could overcome the TTFF problem by using the agps software from [1] It loads the needed data from the gps chip and uses that the next time you power on the gps unit. I usually get a fix in 2 minutes. If you send the log data to a server via GPRS, you might want to use rsync with the --inplace option. The logs will only grow i suspect and i use this method of transferring the gps log from my car to my server at home, while driving. It also helps to chop the log files in smaller parts (+/- 2Mb per file) in case the GPRS connection is not that reliable, a resend will take less time. Roaming data can be expensive, so you might want to look at that too, with your mobile phone provider. Good luck with your project, and keep us posted about the successes/failures, we would like to learn from it. Kind regards, Ed ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community
Re: Freerunner as a mobile gateway -> shipping container
On Wed, May 18, 2011 at 03:19:16PM +0200, Eric Smith wrote: > Main application here is in a sea shipping container. > > The key issues are RF communication (when in a GSM range of course) > and power management due to the long haul journey including journey > overland. Power supply has to be in the form of an additional battery. > > Technical issue is to have minimal size OS and to be low in power > consumption. And robust. If you sleep and only wake up at intervals, you should anticipate some difficulty acquiring a GPS signal every time you wake up. The GPS in the Freerunner is really designed to make use of A-GPS and if you can't do it because you are at sea and far from any network signal, it can take a long time to get a position. We have sometimes seen it take over 40 minutes to get a good fix (unit mounted on an aircraft glareshield). -Phil ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community
Re: Freerunner as a mobile gateway -> shipping container
On Wednesday 18 May 2011, Eric Smith wrote: > Thanks Al, > > Main application here is in a sea shipping container. Good luck getting a signal when they're stacked! I guess you can find somewhere to stick the antennae where they won't be too vulnerable and have a fair chance of getting a signal. > The key issues are RF communication (when in a GSM range of course) > and power management due to the long haul journey including journey > overland. Power supply has to be in the form of an additional battery. Battery, efficient dc-dc converter, y-cable. Do some current measurements and size accordingly. > Technical issue is to have minimal size OS and to be low in power > consumption. And robust. OpenEmbedded, OpenWRT, debian would all work. Choice is probably more personal preference and familiarity than anything technical. FSO provides control via dbus for most stuff if you don't want to do the low level stuff yourself. Remember to turn the GSM and GPS off before suspending! > All ideas welcome. Sounds like a bog standard monitoring job. Do you need something as powerful as the moko, or would an AVR do the job? > Thanks > > > On Tuesday 17 May 2011, Eric Smith wrote: > > > Hi > > > > > > I am considering using the Freerunner as a mobile gateway to track > > > GPS on a vehicle and to receive data from wireless sensors in the > > > vehicle and send the sensor data and GPS data through GPRS. > > > > > > We may need to plug a customised wireless device into the freerunner > > > usb. An external GSM and GPS antenna will be used. The device will > > > have to run reliably and be robust for 8 to 12 weeks, so that means > > > a customised battery. > > > > > > Power use efficiency means putting keeping the device in low-power > > > consumption mode for most of the time and waking every 30 minutes > > > (say) for polling and transmitting. > > > > > > Has anyone implemented such a solution or has ideas about feasibility? > > > > Nobody has talked about doing this IIRC, but it certainly sounds > > feasible. External power can be supplied via the usb y-cable > > arrangement, so shouldn't be a problem. atd-over-fso will let you wake > > from suspend to do what you want on an interval. ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community
Re: Freerunner as a mobile gateway -> shipping container
Thanks Al, Main application here is in a sea shipping container. The key issues are RF communication (when in a GSM range of course) and power management due to the long haul journey including journey overland. Power supply has to be in the form of an additional battery. Technical issue is to have minimal size OS and to be low in power consumption. And robust. All ideas welcome. Thanks -- - Eric Smith Al Johnson said: > On Tuesday 17 May 2011, Eric Smith wrote: > > Hi > > > > I am considering using the Freerunner as a mobile gateway to track > > GPS on a vehicle and to receive data from wireless sensors in the > > vehicle and send the sensor data and GPS data through GPRS. > > > > We may need to plug a customised wireless device into the freerunner > > usb. An external GSM and GPS antenna will be used. The device will > > have to run reliably and be robust for 8 to 12 weeks, so that means > > a customised battery. > > > > Power use efficiency means putting keeping the device in low-power > > consumption mode for most of the time and waking every 30 minutes > > (say) for polling and transmitting. > > > > Has anyone implemented such a solution or has ideas about feasibility? > > Nobody has talked about doing this IIRC, but it certainly sounds feasible. > External power can be supplied via the usb y-cable arrangement, so shouldn't > be a problem. atd-over-fso will let you wake from suspend to do what you want > on an interval. > > ___ > Openmoko community mailing list > community@lists.openmoko.org > http://lists.openmoko.org/mailman/listinfo/community ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community
