Power, software, after-thoughts


While having a GPS-receiver inside your GP2X is nice, it's even more nice if you're able to switch it off: the GP2X isn't that easy on the batteries and the GPS-module adds a 100mA to the usage of the GP2X. I first of all tried finding some unused GPIO to see if I could use that, but to no avail. I then decided to add a microcontroller into the equation: normally, the GPS-module would stay off and the serial line would be free for debugging, but as soon as you set the serial port to 4800 baud and sent a 'magic string', the microcontroller would turn on power to the GPS-module and the serial port would become a GPS-port. That way I could keep the software simple too: non-GPS-aware software doesn't have to be modified and GPS-aware stuff only has to send the magic string first.

I decided on a ATTiny13, because I had these lying around and they're just 8-pin DIP-units with an integrated oscillator. Some hacking and firmware-programming later, my GP2X looked like this:

My GP2X now is a 3-CPU unit ;)


As far as I know, I'm the first to connect a GP2X to a GPS-device, so the software for this is a bit... errm... missing. I am planning on creating some kind of moving-map-thingie tho', using SDL that should be a breeze. I did test the stuff using some usb-telnet-piping-fifo-gpsd-magic: by piping the nmea-strings to my PC, I can run software there and test the setup:


I really think I'm completely out of space in my GP2X now :) While I should be able to put in a few more chips, something like an internal GPS-antenna unfortunately can't be fit there. Luckily, I'm not quite sure about what more I can think of to put inthere :)

The GP2Xs processor should have 4 serial ports. 3 of them seem to get detected by the GP2X-kernel: ttyS0, ttyS1 and ttyS2. Unfortunately, I could only get the first one to work: I tried everything I could using stty but the tx interrupt count of the other two ports remained a steady zero, which basically means I don't even have to try and look for the places where I can electrically pick up the signals. Too bad, I'd rather have a dedicated serial port for the GPS-receiver.

If you decide to build this too and want the software for the microcontroller, please drop me a mail. The code hasn't been cleaned up enough for a public release, so I won't put it online till I know there's a demand for it.

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nim wrote at 26 Dec 2007, 19.02:

any updates? have you put together or adopted some gps client software on the gp2x? you think it'd be difficult to write something for usb/bluetooth gps receivers? btw: have you thought of adding bluetooth to inside your gp2x? :)

peca wrote at 7 Sep 2007, 21.18:

Amazing!<br> I's really greate. But what about real time clock? Even with separate lithium battery. RTC will be very usefull and turn this console to real pocket computer.<br> Any idea?

Katmaļ wrote at 14 Jun 2007, 18.05:

Nice hack man :D, from Dutch soil, i can tell ;) The GP2X has countless possibilities. Keep this work up, one day everyone's walking with one of these jewels instead of a PSP or Nintendo DS.

Dfcnvt wrote at 12 Mar 2007, 11.05:

Something came to my mind, You can use the GPS as an input.. To draw a picture while you're walking. or complete the maze game while you're walking.. It'd be cool to use the command term through your walking. Make a symbol like circle as play music.

apollion wrote at 10 Mar 2007, 2.03:

wow... now since i dont have a GP2x or the ballz to mess with one im going to ask...the GP2x faces great deal of probs in the power department but...ther is a bunch of tweeks that have driven me nuts, one is the built in memory and if in fact the "NAND Flash Memory" chip can be hacked if this is posible then that means skrew "SD" when u got built in memory...up to 2GiB >:). yeah im a bloody brilliant.

Aaron Friedrichsmeier wrote at 7 Mar 2007, 6.31:

Hello, Just recently found out about the gp2x... Ordered one within 48 hours. This thing has been out awhile, I am amazed that they haven't gone just a step further w/ this. Add a small(like breakout card), but (box) EDIT: not box but a simply whole new back cover, just a peice of molded plastic,, that has the following, ONE: either bt or wifi. BT would be much more useful, phone tether, gps, wireless HD, headphones etc. TWO: 2 usb 2 slot towers. instead of sloppy 4 singles all spaced out on the pcb. THREE: A lithium battery to power such additions, AND a crt backup battery for a Frickin clock! Who manufactures a system as sweet as this w/o a clock? FOUR: almost forgot, also the totally awesome video out/sound out. How does that sound? Some second thoughts; could change one of the usb ports into sdcard or compact flash; thus having either extra sd slot(awesome) OR a CF slot, yet another media it could read from (one of my digi cams uses CF. Furthermore could then use a micro drive in, and increase our storage 10 fold. I am totally new to the gp2x, and not yet an owner, (waiting for snailmail), this is just something I see needs done. If this was possible and got done, we would have no problem breaking into mainstream w/ this and get plenty of software support. I work at a circut board assembly plant and know if we got the diagram down, I could access the knowledge and spare work time(tee hee) of many bright minds that could totally make this feasible. programmers, manufacturing techs, engineers etc. I might even be able to get a line going to build them, which one person could w/ four or five machines that sit idle at least 8 hrs a day, build a small pcb thats fits in adding 1/2 inch to part of the back cover... So what? A half inch and a little wieght for what would be the best system out there. Also, why not make the batterys charge via usb and unit powered via usb? I will stop my ramblings. I am very excited to say the least! Questions, more likely comments, suggestions? dharmaATcableoneDOTnet Aaron

Tim Sirianni wrote at 3 Feb 2007, 2.24:

I'd also love the schematic and source. I'm thinking of using a GP2X as the basis for a flight instrument for paragliding. I'd like to connect a GPS and a home-brewed altimeter/variometer so that I can calculate things like where I've encountered lifting air, so that I can go back there if I want to. I could just connect a serial cable to, say, a Garmin GPS, but that's extra bulk and space is very limited on this aircraft. The altimieter is a different story. None of the commercially-available units have real-time serial output that I can determine. So, a pressure sensor and a Basic Stamp handles that... Tim Sirianni sirianni.t at comcast dot net

Rion Motley wrote at 4 Dec 2006, 0.02:

Would love the schematic/source for this project. I was wondering if it would be possible to just build the whole thing into the case of a cheap USB drive (some of those low end 32 or 64 meg ones are only a few dollars now). The idea would be to just gut the drive, use the connector and the case, and put a lithium coin cell inside, and route the external antenna connector out the end. I just hate the idea of soldering directly to something I just paid 280 bucks for. And it's not even here yet! Otherwise, great project. Hit me up - Rion.Motley@gmail.com

kRiMe8 wrote at 15 Oct 2006, 13.54:

Tight hack , do you have GPE on your gp2x and if so does the gps work under it?

el_pango wrote at 14 Oct 2006, 2.11:

Impressive! I'm wondering if the same could be done with an sdio wifi adaptor...

Lost in the Supermarket wrote at 7 Oct 2006, 1.57:

Cool! I have no programming skills so I guess I won't be able to it. I'll check back this site later to see if you'll ever release an easy-to-use script or app for that. Cheers!

natrium42 wrote at 6 Oct 2006, 2.27:

Great job with this hack :) I wish I had a GP2X...

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