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List:       gpsd-dev
Subject:    Re: [Gpsd-dev] feasibility of adding support for emulating a Garmin
From:       Iordan Iordanov <iiordanov () gmail ! com>
Date:       2009-03-25 14:28:14
Message-ID: 43075fc60903250728o1f2956a4l3b488955739dafe8 () mail ! gmail ! com
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Hi Chris,

Thanks for the reply. Some of the things that you wrote show that I
didn't come across clearly in my message. First of all, we are *not*
talking about gluing gpsd to windows. Second, we are not talking about
emulating any sort of hardware. Please see below for the details!

> parts of it aren't as hard or unpleasant as you think - arduino has a
> network serial proxy for reflashing your arduino over the net. that
> sounds like a great place to start building gpsd-to-windows glue.

What gpsd-to-windows glue? Let me be very specific about what this
will do. What I was talking about was mknod-ing a device and writing
binary data to it. Then, linking com1 to this device in
~/.wine/dosdevices, which basically provides a com port 1 to programs
executed under wine.

Now if this binary data that we write to this com1 port actually makes
any sense to Mapsource, then we are in business!

The question was not how to do the above, but how to make this binary
data make sense to Mapsource. The proper way is to write a subset of
the data that a Garmin unit would output when connected to a computer.

> as for emulating an actual garmin... i'd say that sucks frozen dead
> bunnies through bent straws. writing hardware emulators is not fun
> when you don't have full hardware behaviour specifications. the least
> painful way to do this would be to write a standalone garmin emulator
> that is also a gpsd client.

What hardware emulator?! I thought I understood, sort of, how GPS
units output data. We are not talking about emulating any of the
behavior of the GPS unit. All we are talking about is the following.
We connect a NMEA device to /dev/ttyUSB0, and gpsd picks it up and
starts reading data from it. Then, gpsd outputs to its mknod-ed device
file the equivalent Garmin binary data to the NMEA lines that it reads
from the attached device on /dev/ttyUSB0. So, we are talking simply
about translating NMEA to Garmin. I figured that it can't be this
difficult since it is quite obvious gpsd is quite capable of reading
Garmin binary data.

I hope this is clearer and somebody can respond to this more detailed message.

Thanks for the attention,
Iordan
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