> > Do you know what the three interfaces are used for by the way? And do you
> > have any idea about whether the other products using the same PID also
> > have six bulk endpoints (three tty interfaces)?
>
> Yes. There are three [mostly] independent terminals. The older
> devices were normally used with two or three serial ports, and people
> got used to this. While I suppose they could be used to allow three
> users to do separate things on the device, I am using one for a
> bidirectional control port, (sending commands and getting
> acknowledgements) and a second one I am using to listen to binary
> output from the GPS (which makes parsing a little easier). [you can
> create "log" commands that send the data to a different port. So on
> USB1 I can send the command "log usb2 rangeb ontime 1" which will
> display "OK" on usb1 and give me a fresh command prompt, and also
> causes a binary range message to appear on usb2 every 1 second.]
>
> A lot of people [especially ones who have lots of experience with old
> serial-interface GPS devices] will connect one of the ports from one
> device to another device (generally with some sort of radio in
> between) and make them talk to each other. Think of a surveyor
> putting one GPS receiver on a calibrated marker which sends
> differential information to other receivers so they can more
> accurately correct for common errors (such as local ionospheric
> effects and satellite errors). Now days this is frequently done by
> attaching a listener to the appropriate port (say /dev/ttyUSB2), and
> it reflects to a remote webserver-based reflector (wireless internet
> access is much cheaper and more useful than a dedicated commercial
> radio). While the two are talking to each other you still need an
> interface to command them, hence the two or three serial ports (third
> was for daisy chaining, I think).
>
> Anyway, every NovaTel device I have ever seen thinks it has triplets
> of each interface type, [even when the third serial port did not have
> a physical device][yes, even the ones with a built in Ethernet device
> have internal "icom1", "icom2", and "icom3" interface names for
> sending IP traffic.]
>
> For testing your patch I intend on just opening three minicom
> instances, once to each /dev/ttyUSB[0-2], and doing local ASCII logs
> ("log version once"; if you do not provide an interface it defaults to
> the one you sent the command on).
Thanks for the info. I'm responding to this mail with two patches adding
a new "simple" driver for Novatel Wireless GPS receivers for you to
test.
Let me know how it works.
Thanks,
Johan
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