diff options
Diffstat (limited to 'TODO')
| -rw-r--r-- | TODO | 52 |
1 files changed, 5 insertions, 47 deletions
@@ -1,24 +1,3 @@ -** Detect a Garmin USB device - -According to Hermann Kneissel: - -major/minor number won't work, but assuming that if a gps ddevice is attached -to the usb bus the driver is also installed, you may -check /prov/bus/usb/devices -for an entry with vendor 091e/product 0003: - -T: Bus=01 Lev=02 Prnt=03 Port=00 Cnt=01 Dev#= 4 Spd=12 MxCh= 0 -D: Ver= 1.10 Cls=ff(vend.) Sub=ff Prot=ff MxPS= 8 #Cfgs= 1 -P: Vendor=091e ProdID=0003 Rev= 0.01 -C:* #Ifs= 1 Cfg#= 1 Atr=c0 MxPwr= 0mA -I: If#= 0 Alt= 0 #EPs= 3 Cls=ff(vend.) Sub=ff Prot=ff Driver=(none) -E: Ad=81(I) Atr=03(Int.) MxPS= 64 Ivl=1ms -E: Ad=02(O) Atr=02(Bulk) MxPS= 64 Ivl=0ms -E: Ad=83(I) Atr=02(Bulk) MxPS= 8 Ivl=0ms - -this will tell you, that a garmin gps is attached to the usb bus. - - ** Do the research to figure out just what the heck is going on with status bits NMEA actually has *four* kinds of validity bits: Mode, Status, the @@ -53,33 +32,12 @@ relationships are there? * Things not to do: -Here are several things that look like good ideas, but that turn out -on closer inspection to be not possible or not worth the effort. - ** Try to crank the update rate up past 1 per second NMEA doesn't give us control of the update rate, and SiRF/Zodiac chips don't seem to be able to set cycle times below once per second even in -binary mode. Even on a chipset that permitted it, at 50km/h (31mi/h) -that's only 13.8 meters change in position between updates. Faster -refresh might make sense for aviation applications, but not on foot or -in a car. - -** Try to autodetect USB devices - -Sigh. USB scanning won't work. - -The fundamental problem is that there is no GPS device class in the -USB standard. When you get device information about a GPS from the -USB subsystem, all you get is info on the USB-to-serial chipset it's -using. - -This means that GPSes are not distinguishable from other USB-to-serial -devices, in particular USB-to-RS232C adaptors. This is a crash -landing. We could live with the scanning code failing to detect a -GPS that's there, but we can't live with having it mis-identify -another USB device as a GPS. The least bad result from that would -be that the daemon opens and locks up the other device. - -This cannot be fixed, short of USB 1.1 growing a USB device type -and vendor firmare advertising it. +binary mode. (Turns out the reason is that a full NMEA fix report +takes about a second at 4800bps.) Even on a chipset that permitted it, +at 50km/h (31mi/h) that's only 13.8 meters change in position between +updates. Faster refresh might make sense for aviation applications, +but not on foot or in a car. |