Hi! > >> In my simple opinion GPSes shound live in drivers/iio/gps simply by > >> usecase association: streaming out a series of accelerometer readings > >> periodically through IIOs chardevs and other data about the physical > >> world is not any different from the GPS usecase that give you a stream > >> of coordinates on where on this planet you are. > > > > That is... not quite how GPSes work. What interface would you propose? > > It would be good to support error estimates in position/velocities and > > AGPS data upload. > > Sorry for my ignorance. I have not had the opportunity to work > directly with a GPS hardware. Few people have. It is CDMA corelators at the low level. > > Now, NMEA knows about some of the complexity (not AGPS), but gets the > > details wrong. In particular, it would be good to have error estimates > > and velocities from the same moment you get position estimates. > > NMEA if it is this: > https://en.wikipedia.org/wiki/NMEA_0183 Yes. > Seems to be a high-level format such as XML or CSV or any other > $FAVOURITE_ASCII_TRANSPORT format. > > What we want to push into the ring buffer is of course the raw data > that is produced by the GPS hardware, whatever that may be. > If what we have is this text format we should not reverse-translate > it back any more than modem AT commands, it doesn't make sense > I guess. Umm. Its hairy. Each GPS talks slightly different version of NMEA :-(. But yes, we have userland driver called 'gpsd' that understands most of them. Many GPSes have additional, non-NMEA protocol you can switch them to. > So NMEA processing would be in userspace. And if the GPS is just > streaming this text data over to the client, like Marcel says, it is > more reasonable to just feed that up to userspace (no policy in the > kernel). Well -- we normally do hardware abstraction in the kernel :-). > I am however aware of certain hardware such as the ST > Microelectronis STA2062 produced for Garmin, which is *not* > connected to any external chip, and is not talking over serial > to any RSx port, and does not have an embedded firmware running > on another SoC in any special GPS chip. And it is unassisted. I googled STA2062 but it does not make much sense to me. Yes, not everything talks NMEA. Nokia N900 is an example, and it has in-tree driver. > Maybe that is an oddity. In the mobile phone business I guess it > could be more common to have a separate SoC that by way > of standards just stream NMEA data. Sorry, I don't understand. Yes, in mobile phones GPSes that produce something else than NMEA are pretty common. > Fusing that with other sensor data (accelerometer, compass, etc) > is again indeed a userspace task. I hope NMEA includes very good > timestamps. Umm. Timestamps are quite hard to do over serial :-(. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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