On 4/3/08 10:45, Graham Samuel wrote:
FWIW, the GPS device I described is marketed by a European sports retailer, Decathlon, as KeyMaze 300 GH-601. I've found out via the SiRF web site (the device uses a SiRFstarIII processor) that it is actually a rebranded GlobalSat GH-601 - this is GlobalSat of Taiwan. On the SiRF site this is further described at

http://www.sirf.com/success_10.html

Annoyingly the device is not described on GlobalSat's own web site (a site search reveals nothing), but strangely their FAQ pages provide a little info about downloading firmware for it etc. I suppose this means that either the thing is obsolete or else my retailer Decathlon has made an exclusive deal to market it - they are certainly selling it quite vigorously. I tried emailing GlobalSat to see if they have any more information available, but they didn't reply. I guess they don't deal with consumers.

The device comes with a bit of PC software which is just about adequate, but I would not say that it was well-written or complete - its UI is crude and it doesn't even help to file all the information which it extracts from the device, and indeed it may be throwing away information (such as timestamps) which is just not visible to the user.

It looks to me as if my wish to create better software for it (on a Mac primarily) is pretty much a dead end - although if I can get hold of a serial-to-USB converter I might be able to experiment a bit.

...not wishing to stop you from getting back to your day job, but you might not be completely at a dead end.

AFAICT, almost all GPS devices are using SiRFStar II or III as the actual GPS chipset. (And FWIW a very large number of them are using Globalsat technology wrapped round that, regardless of the name on the box.) And at root these things output serial; so they are glued onto (I don't know much about electronics, can you tell?) a serial-USB chip in order to give them a USB interface.

There seemed when I was working in this area to be two main sources of the latter: FTDI and ??Prolific?. Although the devices I was working with were Windows only, I was able to find Mac drivers for both of these things with a bit of googling on the net (because other products are using the same chipsets, and are marketed with Mac software). Once I got these installed I could simply open a "port" called /dev/cu.usbserial, and found that I was talking to the GPS device as if it was a serial device. So in fact Rev was dealing with a serial device; and the actual SiRF chipset was a serial device; there were just a few layers of bridging over USB going on between the two.

So I reckon that there's a fair chance that you could establish communication with the device (though mind you I did this a couple of years ago, on a PowerPC - I've not checked whether Intel versions of these drivers are now available).

However: I was dealing with basic GPS devices, no memory, interface, or anything: so was essentially just trying to talking to the SiRF chip to get the current GPS data in realtime. It sounds as though you might have a device that actually does stuff to record your trace etc when you're out and about, and then you plug it in later and extract info. In that case you're probably talking to some other piece of hardware, which has done the communication with the SiRF, stored the results, and so on; in that case the device you're actually talking to may not "talk serial", and in any case you'd have to reverse-engineer the protocol, which would presumably be proprietary (unlike the SiRF, which talks NMEA). This may not be that impossible (judging by the macam project, which has succesfully created Mac support for hundreds of digital cameras). I believe that there is a handy utility available that lets you eavesdrop on USB traffic, which might be the place to start...

good luck!

- Ben

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