Xbox VGA Bios modification help needed!

Hi,

Thanks for the results.

Sorry about the focus part. I mixed up the hex string from a 100% stock kernel image and the one from Frosty's mod. I corrected both strings in my previous post. You should be able to find the first one in a Frosty modded kernel image just as originally intended.

And finally, was there ever a hacked BIOS based on 5038 kernel? In any case, the hex strings above should always be present in all kernel images (except maybe those related to focus in very early kernel revisions).

 

The Hex editor found the string this time! Replaced it, repackaged the Bios and flashed it.
The result is a green tint in 480p mode and a purple tint in 720p mode. Strange thing is the red and blue signals are present without sync and the green signal isn't present at all! On the green line there's just the sync pulses present.
But why does it show a green tint when there's no green signal?
And why does the behavior change to a purple tint in 720p when there still is no green signal.

 

progress update?

 

Not really, I haven't touch this thing since I posted the values last time. I'll have a look soon.

 

Nothing new from my side either.
Well a new implementation off the "frozen" vga cable. Instead off using the LM1881 i used the LMH1980 that outputs true H and V-sync signals.
Just finished assembling the prototype and it works. Need to test it a bit further but for now it seems to work just fine.
This version is like the frozen vga cable and does not need any modification done to the Xbox. Well except the vga bios off course.

 

This is beautiful. Is the force vga bios released at the end of last year not the pure vga bios you would need to use with this?

 

Excited to hear if you will still have black bars on those displays you had trouble with. If they operate as they should, I wonder why the internal sync method does not work, or what makes the difference.

Nice work!

 

The result looks exactly the same as using the internal Sync signals!
If anybody wants to test the external or internal VGA Mod in person drop me a PM as it would be good to have some people who are willing to test the different VGA bioses out there.
Seems like the Hardware works good and the 480p output looks great! Only the 720p setting has the black bar on the right side...

 

Do you have a schematic for the LMH1980?

 

Just check the datasheet the shematic with recommended part values is in there!
But be warned the footprint is not easy to Use for a breadboard prototype without an adapter.

 

VSSOP package is no problem even for breadboard. I use a 1.27mm pitch version (http://plazma.kapsi.fi/pictures/temp/1.27mm_proto_board.jpg). I'll order some chips and test it. I have 3 Xboxes to modify for Coinops use in Arcade cabinets. I was about to buy some LM1881 but I'll use LMH1980 instead.

 

VSSOP is 0.5mm or so, off the top of my head. The one in your pic is SOIC8 (like the LM1881)

 

Bad_Ad84 is right the LMH1980s i have are vssop8 but should be 0,65mm pitch i think.

@plazma if you like to have an easier way with an already designed Layout i can send you my Layout and shematic files. It's the shematic from the datasheet. Just drop me a PM i have a few boards here.

 

I can wirewrap anything to a breadboard. Here is an 8 pad BGA CSP aprox. the size of a breadboard hole
http://plazma.kapsi.fi/pictures/temp/BGA_proto.jpg
N64 freak: I'll PM you. A ready made schema/layout makes things faster. I can mill a PCB at work.

 

Looks good! You're definitely good at soldering. I'll drop you the files later today!

 

Still some help needed with the Focus part of the bios or does the LMH1980 fixes your job? I see benny already fixed the conexant video encoder part! Nice work benny! If still some help is needed let me know maybe we can fix the Focus part! Need to jump in the focus diagrams!

 

I got the LMH1980 but haven't used it yet. I'll try to fit it inside the AV connector.

Does the VGA bios output only 480x640 or 720x1280?
Or does it scale to higher resolutions if the VGA monitor native resolution is higher?

 

Nope, no scaling whatsoever, the Box will only ever output its native resolution(s). If you aren't using a CRT, your monitor will likely scale it to the LCD panel's resolution, obviously, but that's it.

 

I started prototyping with the chip. I'm assembling a cable where the chip is inside the A/V connector housing.
I left the transistor out and left HD pin unconnected. VGA RGB should have bilevel sync. I'll measure the HD pin and add the missing components if needed. The perfboards is a double sided 1.27mm pitch version. There are components and connection on the other side also.

 

That's some ti(n/d)y circuitry... Not something I'd want to do on perfboard. Don't the holes get in the way more than they help?


In other news, N64's boards arrived and I found a little bit of time to test them. I'm using 'EvolutionX_M8plus_Bios (TRUEHD-VGA-)' on a v1.4 box and a Samsung P2370HD for now. Results so far: The "old school" external VGA mod did not work at all (probably due to lack of sync-on-green support on this monitor, didn't verify that though). The LMH1980 board gives me a decent picture, though not as good as I would have expected. Hsync looks "fuzzy"... I'll have to try another VGA cable.

If you're an idiot like me and forget to change the console out of PAL mode beforehand, you get a partial image that has chunks of its bottom & right borders cut off - but it works well enough to be able to fix your mistake . NTSC, then, looks fine apart from the black bar on the right that N64 already mentioned. 720p did not work (garbled output), at least with XBMC - so I stayed at the default 640x480. Most of the games I tested worked fine, but I found an issue with Beyond Good & Evil looking vertically squashed. Not sure what's up with that, will look into it.

I still have two other monitors to test with, as well as internal VGA to install. Stay tuned.