floating
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Re: RaspberryPi + GPS

Wed Dec 28, 2011 8:43 am

RaspberryPi + GPS, has this been discussed at all yet?

Economical ways to add true GPS to this device would be super useful.

vonvogel
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Re: RaspberryPi + GPS

Wed Dec 28, 2011 8:57 am

floating said:


RaspberryPi + GPS, has this been discussed at all yet?

Economical ways to add true GPS to this device would be super useful.



Why not use a common USB GPS device?

floating
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Re: RaspberryPi + GPS

Wed Dec 28, 2011 8:59 am

Such as? All of the ones I've seen are overpriced — but maybe I"m looking in the wrong place.

jamesh
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Re: RaspberryPi + GPS

Wed Dec 28, 2011 9:04 am

I've been attempting to get a USB GPS device working on an alpha board  - but ran out of time. I think the main problem was lack of serial USB support built in to kernel, then my kernel build broke when I resynced with the git tree and time evaporated due to work.

Once I get a beta, I'll get back to it, as the kernel tree is more up to date now.

The adapter itself cost about £15 from Ebay, a Bluenext device. Works fine on Ubuntu x86so I expect it to be fine on Raspi once all modules are in place.
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floating
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Re: RaspberryPi + GPS

Wed Dec 28, 2011 9:12 am

Awesome James. Thanks for the info, that price isn't too bad. Please update us if you make progress!

fatjonnie
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Re: RaspberryPi + GPS

Wed Dec 28, 2011 3:35 pm

If not already in the kernel, presumably serial->USB driver support could be loaded, as could gpsd allowing multiple applications to access GPS signal simultaneously.

Fat Jonnie

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Re: RaspberryPi + GPS

Wed Dec 28, 2011 3:37 pm

fatjonnie said:


If not already in the kernel, presumably serial->USB driver support could be loaded, as could gpsd allowing multiple applications to access GPS signal simultaneously.

Fat Jonnie


Quite, but in the build I was using serial USB wasn't either static or a module, and when I rebuilt everything I make the mistake of syncing my kernel tree with the latest from dev, and it broke, never to recover. gpsd was running OK, it just had nothing to connect too.
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problemchild
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Re: RaspberryPi + GPS

Wed Dec 28, 2011 3:46 pm

The GPS is seen as a serial device pure and simple no mysterious black magic!

If no USB tty device or similar is created then you need to get USB serial support sorted out  GPSD will allow multiple access to the same GPS data.

Best of luck with your project!

problemchild
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Re: RaspberryPi + GPS

Wed Dec 28, 2011 3:48 pm

BTW Maplin do a nice USB serial GPS stick which works under Linux for £19 !!

darkstar
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Re: RaspberryPi + GPS

Wed Dec 28, 2011 5:20 pm

FWIW it seems this Maplin one has quite a reasonable GPS chipset in it. The same one as used  by Garmin (AFAIK) in their current Forerunner/Edge series. My Forerunner's reception is far better than the earlier model; that one would get confused by tall hedges. The current one will work inside some houses.

Pity Garmin's firmware isn't as good as the hardware.

cmduarte
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Re: RaspberryPi + GPS

Sat Dec 31, 2011 5:16 pm

DealExtreme has both GPS modules and Simple serial-Bluetooth modules. The BT module I have just ordered is set up for Arduino connectivity with 4 pin header it works on 3 volts, The GPS module (SirfStar III) module that I purchased has a little cable that is also 3 volt serial.  Note the GPS module was actually more expensive than a RasPi would be ($28 US). Also the BT module does not have great range but I have seen where someone attached a better/external antenna and had a good measureable 10 meters + range, with this you could use a BT GPS.

CookieMonster
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Re: RaspberryPi + GPS

Mon Jan 02, 2012 12:17 am

vonvogel said:


floating said:


RaspberryPi + GPS, has this been discussed at all yet?

Economical ways to add true GPS to this device would be super useful.


Why not use a common USB GPS device?


USB models cost more and usually require a driver added to the host system.

TTL serial interface modules are smaller, lighter, cheaper. They are not hard to find:

http://www.sparkfun.com/categories/4

https://store.diydrones.com/category_s/10.htm

jamesh
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Re: RaspberryPi + GPS

Mon Jan 02, 2012 10:40 am

Cookie Monster said:


vonvogel said:


floating said:


RaspberryPi + GPS, has this been discussed at all yet?

Economical ways to add true GPS to this device would be super useful.


Why not use a common USB GPS device?


USB models cost more and usually require a driver added to the host system.

TTL serial interface modules are smaller, lighter, cheaper. They are not hard to find:

http://www.sparkfun.com/categories/4

https://store.diydrones.com/category_s/10.htm


On the other hand, they are about $25 and (almost) already work on the Raspi,  and require no soldering or custom software.
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Tomo2k
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Re: RaspberryPi + GPS

Mon Jan 02, 2012 7:01 pm

Perhaps oddly, USB GPS modules are available for lot less than Sparkfun charge, and around the same price as the bare chip from DIYdrones.

I will be getting one of the Maplin 16 quid units, and perhaps ripping it to bits to bypass the USB link depending on what chipset I find inside. At that price I can afford to mess about with it.

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Re: RaspberryPi + GPS

Mon Jan 02, 2012 7:06 pm

I'll be interested to see what people do to ruggedise a system like this. My own GPS gets a hell of a lot of abuse; it's been dropped in cow pats and rinsed in rivers, bonked into rocks and trees as it swings on its lanyard, and trodden on. What sort of measures do you plan to take?
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CookieMonster
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Re: RaspberryPi + GPS

Mon Jan 02, 2012 11:40 pm

JamesH said:


Cookie Monster said:


vonvogel said:


floating said:


RaspberryPi + GPS, has this been discussed at all yet?

Economical ways to add true GPS to this device would be super useful.


Why not use a common USB GPS device?


USB models cost more and usually require a driver added to the host system.

TTL serial interface modules are smaller, lighter, cheaper. They are not hard to find:

http://www.sparkfun.com/categories/4

https://store.diydrones.com/category_s/10.htm


On the other hand, they are about $25 and (almost) already work on the Raspi,  and require no soldering or custom software.


Almost already work? Easier than one that uses the serial port? Doubtful.

That would only be the case if the serial to USB chip in the dongle doesn't require a driver that isn't already in the Linux you've chosen for the R-Pi ... unless the GPS vendor provides one for the ARM ... never seen that.

No custom software? If it works through the USB it should work through the serial port. Nothing more custom here. Same same. For these modules ... all you need to do is open the serial port in a console window and the NMEA sentences roll by. They output the exact same sentences that the USB module does. Fewer drivers and hardware in between.

No soldering? You must be a software guy. Soldering means we've got parts. Yum yum Parts yum.

Borg 1.0
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Re: RaspberryPi + GPS

Tue Jan 03, 2012 1:19 am

I've added GPS to a number of projects, all using serial comms.

Using a "bare" module allows a lot of freedom, in terms of placement, antenna options, selecting the best chipset for your need, power usage, and price.

Futurlec have a couple of large-ish modules, they're a bit pricey but very robust.

Since the serial driver is the least hassle, it allows you to concentrate on parsing the NMEA sentences to derive whatever information you think appropriate.

It would be a great addition to the project to have some sort of universal GPS parser, that way we don't particularly care what's connected, as long as we get standard sentences out that we can play with.

All my designs have used standalone MCUs (eZ80F91, PIC 18F2650, etc) that I write simple init routines (most modules have different warm/cold start timeouts, different register sets, and so on), then I've written a bunch of fairly standard parse routines in C, these have worked porting between the very different hardware architectures with a minimum of hassle.

My linux (*nix) skills are really rusty (the last time I wrote unix code in anger was for SCO unix system V!!!), but it should be possible to create a library and device driver with a minimum of fuss, for someone with better skills. I can't wait to get my RasPi, one of the first things I want to learn is how to get a GPS module working, so there's a lot of impetus here.

If anyone can suggest a "universal" way of getting a GPS module working in linux, in such a way that we can use almost any serial GPS in a standard way, I'm all ears!

TangoAlpha
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Re: RaspberryPi + GPS

Tue Jan 03, 2012 3:19 pm

How about GPSd?

jamesh
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Re: RaspberryPi + GPS

Tue Jan 03, 2012 3:27 pm

Cookie Monster said:


JamesH said:


Cookie Monster said:


vonvogel said:


floating said:


RaspberryPi + GPS, has this been discussed at all yet?

Economical ways to add true GPS to this device would be super useful.


Why not use a common USB GPS device?


USB models cost more and usually require a driver added to the host system.

TTL serial interface modules are smaller, lighter, cheaper. They are not hard to find:

http://www.sparkfun.com/categories/4

https://store.diydrones.com/category_s/10.htm


On the other hand, they are about $25 and (almost) already work on the Raspi,  and require no soldering or custom software.


Almost already work? Easier than one that uses the serial port? Doubtful.

That would only be the case if the serial to USB chip in the dongle doesn't require a driver that isn't already in the Linux you've chosen for the R-Pi ... unless the GPS vendor provides one for the ARM ... never seen that.

No custom software? If it works through the USB it should work through the serial port. Nothing more custom here. Same same. For these modules ... all you need to do is open the serial port in a console window and the NMEA sentences roll by. They output the exact same sentences that the USB module does. Fewer drivers and hardware in between.

No soldering? You must be a software guy. Soldering means we've got parts. Yum yum Parts yum.


What I mean by almost works is the GPSd was running, the USB detected the GPS dongle, an X app to display results was running. but I hadn't got USB serial comms built in to the kernel, so that was the bit not working. Same dongle worked on an Ubuntu system no problem.

It should be plug in and go once the kernel is sorted - must do that when I get time!

Slightly easier than soldering on something and writing a driver.
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ab-fab
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Re: RaspberryPi + GPS

Sun Jan 15, 2012 10:13 am

Hi all,

R-pi looks like a very interesting platform for people who want to get most precision out of GPS. Some tools and hardware already exist in order to reach sub-metric (and almost centimetric) precision. Most of them use Real Time Kinematics (RTK)

This can be good for precision survey, precision drone positionning ...

Geodetic grade hardware proposed by major GPS suppliers is very expensive (several thousand $) but some alternatives are proposed for DIY enthousiasts. R-pi could probably be of interest there.

Here are some good start-points

_ An open source library called RTKlib [1] , with associated tools available for windows (GUI) and Linux (command line)

_ A GPS module with usb connector on one side and antenna connector on the other side. It is designed to output raw measurements at 20 Hz (20 measurements / sec). This is far beyond what a Sirf III module can propose in terms of post-treatment capabilities. According to Michele Bavoro, such module price is about 90 € for a single shipment.

It is also nice to be able to chose the type of antenna, in order to get the best performances / size / cost compromise

_ Some farmers are expecting almost centimetric precision in real-time during some periods. Lance Lefebure is a GPS hardware reseller and also RTK / DIY enthousiast. The development he does for autocontrol of farming machinery and communication between base-station and rovers is amazing.
More infos in [3], [4] and a nice video in [5] showing the precision expected

[1] http://www.rtklib.com

[2] http://www.onetalent-gnss.com/.....ers/yuan10

[3] http://lefebure.com/

[4] http://www.thecombineforum.com.....e-gps.html

[5]

Ianw
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Re: RaspberryPi + GPS

Sun Jan 15, 2012 2:16 pm

The main issue with creating an RPi GPS system isnt so much the hardware but the software side. On the hardware side its most likely that you will be getting data via serial be it via the GPIO possibly with a microcontroller in the middle or through an FTDI chip on the USB. The tricky bit is error correction and drift calculation in software and averaging (smoothing) the data.

If you would like to find out more about microcontrollers/gps interfacing there are lots of autopilot RC aircraft systems out there which cover everything from correction, altitude calculation, speed, distance algorithms etc

http://arduino.cc/playground/T.....orials/GPS < this tutorial covers using an arduino for the GPS interface,however it covers a number of things that would apply equally to the RPi

Another good resource is ardupilot

Also another article on the basics of GPS and terrain mapping: http://www.cmtinc.com/gpsbook/#chap8

Hope this helps!

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