Communications with bluetooth GPSr

I am looking at getting an Holux GR-240 to use with a Palm. The
manual shows the various NMEA sentences that are supported. One is
listed as "Choice of GLL or SiRF binary format". A web search found
info on an NMEA $GPGLL sentence, but of course there is no info on the
SiRF binary format in the manual. I found a SiRF manual that covers
the SiRFstarII. I assume this is very similar to the SiRFstarIII
which is in the Holux unit I would like to use.

Will the Holux unit support all of the commands documented by SiRF?
Anyone worked with these modules before?

The Sirf III is very similar to the Sirf II. If you want to explore
the various Sirf options, download the "sirfdemo" program. It allows
you to put the Sirf into binary mode and to view the various
messages.

Do NOT change the port rates or power settings. Sirfdemo allows you to
put the Holux into a state where the Sirf chip no longer talks to the
bluetooth controller. If you are playing with protocols, you might
want to order the USB cable to help you recover from mistakes. (Normal
users would not encounter this problem.)

Here are some program comments about the Sirf III.

// Background on Sirf Messages
//
// General parsing of messages
// Sirf messages are "big endian", with the exception of 64 bit
values
// which have the two 32-bit halves swapped. This is typical of the
"ARM"
// microprocessor used internally in Sirf receivers. There is some
confusion
// in the documentation however, and there may be versions of Sirf
which
// do not swap the 32-bit halves.
//
// The RawSirf interface uses the following Sirf output messages
// Navlib messages.
// Contain pseudorange and carrier phase for one satellite,
// The time information is uncorrrected and reflects clock drift.
// The doppler is reported in the "freq" field. Oddly, "freq" is
in
// meters, and you have to divide by wavelength to get Hz.
// This value is not corrected for clock drift,
// so you need to subtract clock drift to get the actual
doppler value.
// On the Sirf III, carrier phase and timetag are always set to
zero.
// Navigation message
// Contain X,Y,Z position data, as well as status information
// The position data is only used as an inital estimate, but the
status
// information ensures we only collect data once the receiver has
a good fix.
// Clock message
// Contains the epoch time as well as the corrected clock
information.
// In general, clocks don't have to be accurate for double-
differencing,
// but with Sirf the clock drift is needed to calculate the
Doppler.
// Drift is only reported to the nearest nsec which limits the
accuracy of
// the doppler values. The errors may be significant enough to
prevent you
// from using integrated doppler as an alternative to carrier
phase on the Sirf III.
// 50bps messages
// These are the raw ephemeris messages sent by the satellites.
// They contain the same data as Sirf's "ephemeris" message,
// but the "epemeris" message didn't work on the Sirf III.
//
// According to documentation for the "initialize data source"
command,
// Sirf will output the above messages when Sirf is placed into
"Navlib"
// mode. With the Sirf III, we need to enable the messages
explicitly.
// We still ask for "Navlib" mode just in case Sirf II needs it.
//
// With each epoch, messages are sent in the following order:
// - Navlib messages. On the Sirf III, the time tags are zero and
the tow
// is the same for each satellite in the epoch.
// - Geodetic Navigation Message
// - Navigation Message
// - Clock
//
// If Sirf isn't calculating positions, the Navigation and Clock
messages
// may or may not be present.
//

Thanks for the info. What were you quoting?

I expect to get the USB cable. I can't find where they have a serial
cable for the 240, although they have one for the 236.

The SiRFdemo program only runs on a windows PC. I guess I can play
with it there, but I would like to get a similar program for the Palm
which is what the device will be used with. So far I have only found
generic programs to display the NMEA messages. Even the Holux Viewer
program only runs on WinCE PDAs. I guess I need a terminal emulator
since bluetooth looks like a COM port to the software, no?

My own code. You can download sources from
www.precision-gps.org. (src/library/receivers/sirf/RawSirf.cpp)


My experience with with the 236, and I've been assuming
the 240 is pretty much the same.


It depends on what you are trying to accomplish. It is much easier
to do development on Windows then PalmOS. You might look
at J2ME, a java platform targeted for cell phones and PDAs. You
can do the development in an emulator running under windows or linux,
and download to almost any small device when you have things working.

For a good example of how to program with a GPS under J2ME, take a
look
at www.geotracing.com. They have an J2ME client which uploads your
position to a webpage in realtime, using a cellphone and a bluetooth
gps.
The sources are available from "codehouse".

I've been fairly satisfied working with the "almost Java" Superwaba,
(www.superwaba.com) toolset. I've written an application for collecting
field data linked to GPS coordinates. The program talks to a bluetooth
connected GPS receiver, parses the NMEA strings and saves the positions
to a SQL database running on the device. The application runs great on
WinCE, PalmOS and Win32. I have not tested the application on Symbian or
Linux desktop yet, but I don't anticipate any significant issues. My
application is called gpsDataLogger and can be downloaded from either the
Superwaba/samples webpage or via Sourceforge. No mapping component yet,
but I am working on it!

The Superwaba documentation is excellent and there is a fairly robust
development community as well. I found it to be far easier to develop with
that the current J2ME CLDC and CDC constrained profiles.

If you are interested in looking at the raw NMEA strings on the fly, I'd
suggest tty.exe. It is a valuable little WinCE app for GIS development.

Have fun!

Glenn


On Sat, 28 Apr 2007 12:31:28 -0700, John wrote: