kylebassett at gmail.com
Fri Nov 30 04:45:22 CET 2007
I do see a few benefits to a device which is just a GPS radio, like what Ian
has stated. Would their be any legal ramifications to a reverse-engineered
open source binary interpreter for the GPS radio? I saw a few people
mention government concerns with having access to a very accurate GPS
device, but what about Global Locate's license agreement (if any) by using
their hardware? I think a "GPS radio" would make an excellent open source
project; allowing access to the specifics of GPS (theory) not available with
I wouldn't mind working on this project.
On Nov 29, 2007 9:46 PM, Ian Stirling <OpenMoko at mauve.plus.com> wrote:
> Doug Sutherland wrote:
> > Mikko wrote:
> >> 2) Yes, it can make sense not to have a bazillion CPUs on board from
> >> various perspectives.
> > I evaluated no less than 25 different GPS modules some years ago
> > and compared them in all important aspects. Every single one had
> > a microcontroller onboard. I do not agree that it makes any sense
> > at all not to choose one of these types. They are down to the size
> > of a thumbnail almost. Is the microcontroller a CPU, technically
> > yes, but it's part of the receiver, and you want to do all this fancy
> > GUI and not suck the life of the battery from ARM9 usage. It is
> > a good thing they ditched that GPS. It is now standard that any
> > GPS module does have a microcontroller inside, most commonly
> > some variant of ARM7, super low power, you never deal with
> > any firmware.
> (sorry for the late response)
> To clarify why it might be nice - yes there are simplicity benefits
> from just using a GPS with a NMEA output (or at least with that as an
> If the existing hardware had an open-source driver (there was some
> progress towards such, but this has stalled since it was announced it
> would not be used in GTA02) then many of these objections go away.
> The following is based on preliminary work that has not been completed,
> and due to the lack of work on the current GPS may never be.
> The device is basically only a software radio, that does the absolute
> minimum to enable the host to avoid having to do hard-real time stuff,
> 115200 baud serial is just fine.
> As I understand it, the following things are possible, which are
> difficult to do with 'normal' chipsets.
> Wakeup once every 3 minutes for 1s, to maintain lock on satellites,
> keeping a reasonable (say 50m) position accuracy, with the GPS totally
> off in the interim. This (with the mobile phone part off) uses a very
> small amount of power, enough to track for around 8 months.
> Logging all parameters of the signal that the chip measures in hardware,
> so that the track can be post-processed for better accuracy.
> The option of delaying the output of the signal by 10s+, and being able
> to smooth the output based on the 'future' movement, not just the past.
> (this can dramatically improve tracks round sharp corners)
> Being able to feed in information from the accelerometers to go into the
> position solution. (this is mainly useful in cars - the accels give you
> good turn rate info)
> Using even 'failed' GPS satellites as position sources, with the aid of
> AGPS (however, this is unlikely to be of use unless the GPS system
> stops being maintained)
> Easy tradeoffs between output noise and update frequency - few devices
> support updates faster than 1Hz.
> User-provided AGPS correction information.
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