Another UPDATE: Well, Hobbyking have been installing open source firmware on their gadgets out of the box lately. The G-OSD has finally gone the same way. I guess this article is still relevant if you get an old one, but if you want to go pre-flashed, here it is: G-OSD 3
UPDATE: Wow, it pays to review an article every now and then... I still use my G-OSD for FPV, as it's a great value little unit. There are also a number of other GPS units that you can plug in and program to better refresh rates.
One important update to this article is that Hobbyking have brought out the latest version of the G-OSD: it's cheaper and supposedly a little better, though I can't tell the difference besides the price TBH.
My first few FPV flights were very basic and simple - cheap 200mW system, stock antennas, no OSD, all kept pretty close to base.
Yeah, it seems like only a couple of weeks ago... Hang on, it was! I'm a newbie FPVer, and proud of it. So what can a newbie teach you that you can't learn from RCG, or Bruce from RCMR, or Dave W? The answer is how to from a newbie perspective.
After my first couple of flights, I knew I needed three things to keep it interesting and make it safer. 1. Power consumption (I ran one battery flat, thankfully close to home, and had a friend bring it in for me); 2. an arrow pointing toward me (I got horrendously lost flying from a hill, as I couldn't find myself anywhere) and 3. better antennas.
Antennas are pretty well covered by, well, lots of people. I liked Bruce's method, keeping the shielding intact rather than bunching it in 3 or 4 strands (personal preference). I made up a set of cp antennas for my 900Mhz system and the reception is rock solid.
For needs 1 and 2, I needed an OSD. I'm on a very tight budget and wanted the cheapest, effective thing with a home arrow. I noticed HK had the G-OSD, but was amazed that it didn't have this feature!!! What's more, it had plenty of other faults! But then I spotted some magic words hidden in a review... 'open source'.
I recently reflashed my Turnigy 9x and wonder how I put it off for so long. I still have my AVR programmer, I've got my mad soldering skills, why not turn a froggy $40 OSD into a princely instrument set!?!
For those that have done the 9x, beware. The instructions have been revised many times and it's pretty darn simple to do. CL-OSD, while wonderful (all props to Callelj and other who wrote/refined this), is not so easy and the instructions are hard to follow for a non-programmer like me. WinAVR might as well be Japanese to me. Even for soldering the programmer on, the pads are really close together!
Unfortunately I can't help you much with the soldering bit - just be careful and quick, while also taking your time. A sharp soldering iron tip is essential. Remove the heat shrink to reveal the pads. For cable to pad layout:
Wire 1 (MOSI, the red one) connects to the left-most pad (let's call it 1).
Wire 2 (VTG) connects to pad 6
Once your soldering is done, plug the programmer into your USB. If you haven't installed the drivers, here's where they are: AVR drivers. I had trouble getting the drivers to work. I installed them eventually by opening up 'Devices and Printers' and right clicking on the icon for the programmer to go into 'properties'. Then click on the 'hardware' tab and select properties again. Click on the 'driver' tab and then select 'update driver'. Select the driver folder from your computer (where you unzipped it) and hey presto... If it doesn't work, try permutations of this until it does.
Anyhow, once your programmer is working, I found the most simple program to flash the firmware with is eXtreme Burner AVR. Once you've downloaded this, you'll need to download the eeprom and hex files for CL-OSD. Right click the links and 'save link as...'.
Insert your AVR programmer if you haven't done so already, and open eXtreme burner. Click on the 'chip' menu and select 'ATmega88'. Click on 'file' and select 'open eeprom file'. Select cl-osd.eep and click ok. Then, click on file again and select 'open flash' and choose the cl-osd.hex and click ok. Then click on 'write all' and it will write both the eep and hex files onto your G-OSD!
If you've only written the hex file on there, you'll get white blocks where the letters and numbers should be, as the alphanumerics are defined in the eeprom programming.
Also, if your LED no longer works when you power up, don't panic. It'd not dead until you see smoke! Just try and reflash it again. When the programming makes sense, the light comes on.
I'll let you figure out how to wire the OSD up, but here is what the display should look like in the end:
Once again, props to Callelj for writing this piece of genius firmware, and to those who refined it.
Remember that this is a $40 OSD. There are still plenty of little tweaks that people have been making to the programming. People have still reported the need for GPS coordinate and altitude calibration, which I have no clue how to do and is apparently case-by-case different. The folks at RCG are pretty helpful though, and there's 111 pages on this mod to sift through for tech support if you're scared to ask questions.