Markus, thanks very much for your reply, I'm now considering only
Overo, more below...
On 30 October 2010 08:01, Markus Svilans <msvilans@...> wrote:
> Hi Brian,
> I had some thoughts regarding your project.
> Based on a few messages I've read on the mailing list in the past few
> weeks, I would recommend using an Overo, as it seems much more actively
> used compared to Verdex, and you are more likely to get responses.
> On 10/29/2010 0:17, Brian Modra wrote:
>> I am thinking of using:
>> Gumstix Verdex Pro XL6P COM
>> ... and plugging in a radio module for 868MHz 500mW from Instrotech
>> (to reach a few Km line of sight) via RS232.
>> (This is for a vehicle tracking application.)
>> At this point, I've just found the Gumstix web site and mailing list,
>> so I have a few naive questions:
>> Can I plug 3 of these boards together like this?
>> Limitations regarding programming? (compared to Overo) I'm very happy
>> to use Linux.
>> I'm wondering should I use an Overo board, but don't see GPS and RS232 for them.
> Re: RS232
> The Overo COM itself does not expose any easily accessible serial ports,
> but you can get a Summit or Tobi expansion board, which provide the
> serial port pins on the 40-pin header. The catch is that the Overo
> serial ports operate at 1.8V logic level, not the typical RS232
> voltages. To interface the Overo to other devices that operate at
> signals other than 1.8V, you have to use a logic level converter. For
> These things are really easy to wire up with a little bit of soldering.
OK, but I'll also look for a USB modem.
> Re: GPS
> There are plenty GPS receivers out there that you can connect to an Overo.
> You may consider one of the Garmin GPS 18 models, for example:
> This is a somewhat expensive (US$200) unit but has the advantages of
> being USB powered (less hassle because you can just connect it to the
> USB port on the Tobi or Summit expansion) and a fast 5Hz position update
> rate. It's also sealed in a tough hockey puck type enclosure, which
> might be a plus if you are operating this device on a mine site. If you
> don't need the 5Hz update rate, there are plenty of slower 1Hz models
> for less $$. Sparkfun has a few interesting ones as well.
very nice 5 samples/second. also I heard that an Overo expansion board
with GPS is imminent.
> In a nutshell, I would suggest for you to look at:
> - Overo+Summit or Overo+Tobi combination
> - use a logic level shifter to connect your Instrotech radio RS232
> - plug a USB powered GPS into the USB host port on the Tobi/Summit
> - alternately you could also use an RS232 GPS receiver, with a logic
> level shifter of course
> Since the radio and GPS supply their data via character devices in the
> Linux system, it should be pretty straight forward to write a Perl or
> Python script to acquire/process/store the data.
yes actually I'm writing all my code using C++ so no problems to get
> You probably have seen this mentioned here already, but you have to use
> a USB high-speed hub with the USB host port on the Summit and Tobi boards.
> The ability of the Overo to connect to a wide variety of devices is
> astounding. In my case, the biggest challenge soon became finding
> smaller and smaller components to do the various tasks.
>> I don't want to use Wifi because it would stretch its range, but I
>> wonder has anyone has made a 868MHz 500mW expansion board for one of
>> these Gunstix boards?
>> Has anyone experience using 802.11 (with good antennas) in an open cut
>> mine application? (I expect it would work, though a bit unreliably, if
>> there were a number of repeaters around the perimeter of the mine).
> I don't have any experience with using WiFi over long distances, so I
> will leave this question for someone else.
If anyone knows of a 3rd party 868MHz 500mW radio modem expansion
board for the Overo, I hope to hear from them.
What I need is:
- radio network in a 2-5km line-of-sight radius of e.g. 20 units. WiFi
may work up to 3km line of sight, but it may be too unreliable.
- data storage (e.g. 32GB micro SD will work)
> Best regards,
Thanks for your help.
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