Bacteria's project - Modding a GP2x....FINISHED

Trying to get homebrew running on your PSP? Want to add a screen light to your Game Boy? Trying to figure out how to work your GP2X? By popular demand, discuss it in here! (This forum is for pre-built handhelds, NOT custom made portables!)

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bacteria
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Post by bacteria »

Yes, it works, but I want to make it smoother so it doesn't feel like anything catches, so I need to spend time this morning fine tuning this.

Turned out the main issue I had with the battery contacts before was that the plastic strips I had previously used to keep the screen from falling out the front of the system made the case slightly bowed when laid flat, which contributed to the wires getting slightly loose - anyway, fixed now, as the contacts to the batteries are no longer making contact with the case itself as originally.
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bacteria
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Post by bacteria »

Did a fair bit of work on this so far today. I spent a while re-wiring the S-video connector, relocating the other a bit, general cable reducing and tidying. The screen seems to rotate fine now. This has been quite a challenge - on a standard system you can hot glue all the wiring in place and know it won't move - with this project, a fair bit of the wiring needs to move, so it is necessary to hot glue those wires you can, tie back others and let the remaining ones move freely and not snag on stuff.

I wasn't happy with the digital joystick, I didn't feel it felt right and was over responsive; also it was the weak part of the system as it was hard to mount in the case properly due to its shape. I resorted to "Plan B" which I had allowed for in my original design - a D-pad.

I stripped apart a NES controller (I have a few of these, great D-pads and easy to mod with), hacking apart the mobo parts I didn't need, used a knife to strip it down on one of the edges to fit.

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The NES controller is held in three places, one of which is secured by a screw, so I cut the outer part of the case (the grey bit) into shape, so when assembled it is secure, minimal, and looks like this:

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I then positioned it inside the case, turned the system over to its front, traced the outline with a CD writing pen, removed the NES part and dremelled out the shape. I made it so the NES part fitted snugly into parts of the hole, so it was easy to hot glue it in place (inside the casing). The NES D-pad cross only sticks out of the NES controller about 3mm or so, so I couldn't mount the NES outer casing part flush with the top of my perspex, as I wouldn't be able to press the D-pad as it would end up being flat against the mounting board which will be on top of the perspex front (with the thin card on top), so I basically raised the NES plastic to the equivalent height of a piece of mounting board along side it, as in the pic, to compensate.

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I hot glued the NES casing to the inside of my casing, then put in the cross and rubber membrane, followed by the NES mobo part. I used a half-length screw to screw the mobo into the NES construction to keep it firmly in place, and also easy to remove if I need to.

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D-pad works nicely. Yes, the D-pad is mounted straight, in case you wonder from the pic!

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I am in a position now to start making the other sides, and the shoulder buttons.
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bacteria
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Post by bacteria »

Ok, end of project work today, back tomorrow.

Made the sides out of perspex and cut hole for tact switch on each side. There was so little space between the edge and the battery that I had to shave some of the plastic off the tact switch rear so I could attach the sides. I had planned it like this from the start, but it was still tight.

Pic of the sides. A few blobs of hot glue secures the sides to the casing, and one 90 degree strut holds it securely. Once I know everything works fine and all cables are tucked away nicely, I will add more of these triangles and make it completely rigid.

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toby dawg
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Post by toby dawg »

Nice. Thats lookin good.
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ShockSlayer
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Post by ShockSlayer »

Will you adopt me?

I still cant believe you are going to have a rotating screen. I keep thinking about: Where the hell did you come up with this? However, I can see all the benifits and problems you might have. Just make sure that you have long wire and stong connections!

SS
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bacteria
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Post by bacteria »

SS - :D

It comes from my love of games like Galaga (and Pacman, Pengo, etc). On the GP2x the MAME emulator has the ability to play games portrait as well as landscape; many arcade games are landscape, however the old ones tend to be portrait, so if you play them landscape you end up playing the game on about 2/3 screen size and it being slightly out of shape. For these games on the MAME emulator you can play the game portrait, which means holding the GP2x on its end (a bit awkward). Add to this that the GP2x output is not exactly crisp video quality, although the PSone screen is the same resolution (320 x 240) which helps as it doesn't force the GP2x to skip lines, and of course the PSone screen is not of the same video quality as a crisp TFT panel, games full screen are perfectly acceptable on the PSone screen but not if scaled to a smaller size.

I started off by thinking about putting a couple of buttons near the D-pad for this and turning the console round, but of course the D-pad which is normally on the left side in a comfy position would then be on the bottom, hard to use and the system would be hard to hold, which would mean two D-pads instead of one, and extra buttons. Messy. That's why I decided the option was to rotate the screen itself and therefore use the same buttons as usual. This introduces other issues:

* The D-pad directions need rotating
* The A and B buttons swap with the Vol+ and Vol- buttons
* Securing the wiring (hot glue, tape) to stop the solder joints breaking
* Making sure the wiring is flexible and longer than normal for the rotation.
* Stopping the wiring from catching on other things when moving.
* Changes in thickness as the perspex PSone mobo protector rotates. I had to put some wires above the protector as I had to have access to them, however of course that adds to the overall thickness and can stop the rotation (as it did, I had to re-wire a bit to solve this).
* Keep as many wires away from the rotation area as I can.
* Trying to keep the case to a sensible size. As you see in the pics, I couldn't have made it any smaller, everything "has its place".

I am hoping I made the right decision with using C cells; they are bulky and heavy after all. I didn't fancy spending double the money on sub-C's (max of 4200 mAh) or having a potential portable hand grenade with Li-ions; the only other option was to have used 2 sets of 6 AA's in parallel, but I figured I would get more from the C cells as they are double the mAh than AA's and much fatter, so better equipped to take the drain, especially as the GP2x is quite high drain and I am using the same battery set to also run the unmodded PSone screen (I don't like the lights and darks on an LED modded screen - personal choice!). I won't know this answer until I do final tests.

Anyway, I have most of today for more project work potentially, so will be giving more updates today. I might have some project time tomorrow, then back on Monday for a short time.

UPDATE:

Got all four sides of the case on now, not the corners though yet. The rotating screen is quite smooth now in operation although there was a bit of resistance at the end of the rotation, I might have fixed that now, need to test and further fix if needed. Finished wiring the last wires. Tested system earlier, still fine.

Need to check all the buttons work and are connected next, do the corners to the case, make a series of screw holes to secure the back of the case down properly, test the screen rotation alternative buttons and controls, set the screen contrast level and experiment with the sound so I only need to press one button (ideally) for volume up and one button for volume down, instead of independently (if I can get the levels right). I also need to make back-stops for the screen so it can only turn one way (in case I forget and try to turn the screen the wrong way - this would not be good)!

I am hoping to get most/all of this done this afternoon, let's see how time goes.
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bacteria
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Post by bacteria »

Ahem, I thought I would just test the system, but ended up playing Psycho Pinball (MegaDrive) and Galaga '88 (TurboGraphics) for the last half an hour!

All the buttons work fine, although I did wire the PSone volume buttons the wrong way around (easy to fix) and I got the X and Start buttons wired the wrong way around (also easy to fix). You have to expect things like that!

Anyway, pics of the 4 sides of the case on, it is becoming a proper cased system now. Sound is lovely by the way, these 55mm speakers are great for portables!

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Rear view (excuse the paper tape!). From left to right: two volume controls, three switches (rotation), GP2x soft reset, recharge, on/off.

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Showing the GP2x menu:

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Playing Galaga '88 (TurboGraphics emulator). Pic is clearer on the screen, not a perfect pic:

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I was able to hold the console properly, rather than just flat on the desk; feels nice and comfortable to use. Weight is fine, held in both hands.

:P
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bacteria
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Post by bacteria »

Hot glued some small strips of perspex in place, drilled holes and get the screws in place to hold the case firmly in place. Need to put another one in, one of the sides has a slight curvature to it, between 1-2mm - it looks more than this in the bottom pic, but it isn't.

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Run out of time today, may have some time tomorrow - I need to put system through testing again, now everything is firmly down - it might be that it is too firmly down, or ok, time will tell. There could be issues with the screen turning, or pressure on the wiring, etc. One thing I do know, it is all very snug in there.
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kasar
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Post by kasar »

great!

I really like your nice job.

especially the rotating screen and the transparent box,(Its nice,be able to watch all your project stuff from outside the box)

about the rotating screen, is the rotating range limited? or it can rotate unlimitled?

(I mean if the rotate range is set to unlimitled, maybe the cables can be broken by the movent tension)
Negative_Creep
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Post by Negative_Creep »

That screen isn't level is it?

It's looking nice now, will look really nice with the paint job on and the rotating screen... perhaps I should try a rotating screen mod of my own when I pick up a GP2x..
bacteria
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Post by bacteria »

kasar - Thanks for the comments. I am going to keep the back of the casing clear for a while until I feel confident enough to cover it, because while it is transparent I can gauge how things are moving in there. Having the casing transparent is great for troubleshooting, however looking at the bundles of wiring, hot glue and electrical tape is not pretty!

The rotating screen is only designed to go 90 degrees only, back and forth, that is all it needs to do. The screen rotates anti-clockwise to go portrait mode and clockwise to go landscape. I will put in back-stops to stop it moving against the design, and help to keep the screen level in both positions without moving freely.

Negative_Creep - :lol: the screen is designed to rotate as needed, I didn't adjust it be completely level before taking the pic that is all. Turn the screen by a couple of degrees and it is totally level!! :lol: I will make a back-stop to ensure the screen is set straight as standard, the priority up to this point was getting the system working, then it becomes a case of tweaking the system to iron out any other issues and then making it look nice.

Sure, have a go at a rotating screen when you get a GP2x; although I would recommend using my guide if you want to undertake this project, putting it in a slim case without snagging the electronics or the wiring or making a short has proved to be quite a challenge. Also, the batteries proved a challenge in itself (non-solderable tabs).
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Post by khaag »

When you are confident with it not all coming undone, are you going to do any bondoing to clean everything up and then paint it?
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bacteria
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Post by bacteria »

No, as mentioned before, I will be putting two layers on top of the system:

Layer one - mounting board. This will push up against the D-pad assembly, give me pits to hold the buttons for the tact switches, give a much tidier and tighter rotating circle, remove the flashing top line from the PSone screen (interlacing). This layer will also firmly keep the screen assembly in place and won't fall out. The underside is secured by a smaller perspex circle, I did this a while back, but the top is reliant at the moment on four thin strips of plastic, which is only temporary.

Layer two - the thick paper topping, to conceal the rotating screen mounting completely and make it attractive, cover the exposed D-pad area (except the cross of course), cover to the sides of the case. I intend to put the paper first through my printer to embed lettering and images onto it to make it look really nice. The thick paper (160gsm) will have a couple of coats of varnish on it to protect it from general use and marking.

This will give a perfectly smooth surface so I won't be painting the top of the case; anyway, the turning circle is crude so needs to be made invisible. This is the only way to make it look nice.


I may only need to use some putty to cover the edges from the curved corners to the sides - small areas only. I will paint the sides most probably; else will use the thick paper to cover the area - not decided yet.
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bacteria
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Post by bacteria »

Hit a bad problem. :cry: It turns out that the GP2x hammers the batteries. The cells are running at 7.8v when off, when on however this drops to about 6.6v so although the GP2x can boot up and gives that nice boot up sound from the speakers (powered by the PSone screen), the PSone screen isn't getting enough power to run as it needs at least 7.2v. Yesterday, I noticed the screen starting to wobble a bit after only about an hour of use from cells which had started at about 8.2v. This isn't acceptable.

I only have three options remaining now:

1) add a 7th battery, although I am not sure if I have space for an extra one in the case; problem with this will also be that there is a slight risk of frying the PSone screen if the system is started soon after full recharge. Even then I don't have confidence of long playtime given the facts I have found; may only increase playtime from 1-2 hours - still not worth it.

2) put in extra batteries for the GP2x only; I could put in 2 x 2 AA's in parallel which would give good life, maybe 4-6 hours use, but add further to the weight of the system and have to be removable as they can't be recharged with the main batteries, so this option isn't desireable. Issue of course with this is the PSone screen will lose power at a different rate to the GP2x.

3) forget the batteries altogether, remove them from the system and save a lot of weight in the process. This will mean the system will only run off mains power but at least I don't have to be concerned with recharging batteries, wondering how long I have left before the system loses power. The other thing is that many emulators on the GP2x need you to overclock it in order to get the emulator to play at full speed. The GP2x runs as standard at 200Mhz, although you can overclock it to about 260-305Mhz depending on the one you have. This also draws more power which drains the batteries far quicker. When you change the batteries in the GP2x they can be slightly warm, which indicates the draw the batteries are having to take.

The GP2x is battery hungry, at least all the ones I have had are (3 - first one I broke ages ago, this one, and an unmodded one). You have to use photo grade high drain cells and as high amperage as you can get. Alkaline cells, in comparison, die after about 20 mins of use. Some people on the GP2x forum claim to get about 4-5 hours on two AA's although they often underclock; I get about 50 mins - 1.5 hours or so (admittingly I overclock the GP2x in most cases to play games I want at full speed).

I'm not having a lot of success with using batteries. I figured I would get far more than 1 hour from large C cells, especially as they are thick photo grade 5500mAh cells. I also hadn't expected there to be such a large voltage drop from using the TI card, I thought it ran at very good efficiency. Oh well.

I am lothe to put in more batteries into the system (option 2), it will introduce yet more problems and is it worth the end result? I am doubtful. If I HAD to use the system with batteries, then I would do this as I know it would work; but I play my systems at home or work, and there is always mains power a couple of feet away, so this isn't a problem.

I think I will have to go option 3 and remove all the batteries altogether; keep the TI card to power the GP2x and just use the system with mains power - easy, light and I don't have to worry about the time left before the batteries die and recharge times between sessions - plug in, turn on and play. Simple, light and convenient. :wink:

At least I managed to get the system working with batteries, however they really suffer when using a PSone screen and the GP2x; far far more than I originally thought they would. :cry:


I have things to do for the next couple of hours or so, then I guess I will have to get about trying to remove the hot glued batteries from the system without damaging them, and working carefully to not damage the case. I will keep the C cells for something else in the future.

Never mind, that drawback aside, the rest of the system remains as originally planned. :D

The system will look bare without the cells, I will post pics when I do this later. I will leave the case the same size as it is, with the speakers I use I can't reduce the bottom side size, I could reduce the top by about 1cm max but it isn't worth it and the left and right sides are optimum as they are (needs to be symmetrical after all).
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bacteria
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Post by bacteria »

I am truly addicted to modding (as my wife keeps telling me). I really have to get on with other jobs now!!

I snipped the contacts to the batteries and set about removing them with this rather handy tool, it is just big enough to do the job. Only this is I forgot initially to put electrical tape over the two gripper ends, so I thought for about 2 seconds - "what's that smoke from" then "oh, orange glow" as the battery had been shorted and was starting to catch! :oops:

Anyway, fixed this, I hope the battery is still fine! :oops:

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5 minute job to remove all the cells, I sliced away what I could from the hot glue, then applied the pincers and rocked back and forth until the battery detached as the hot glue released them with a satisfying series of mini cracking noises.

Here are the detached cells: :cry: They gave me lots of grief before I got them working fine...

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All for the best really, I wanted to make the system with batteries, but not knowing how long playtime you have remaining and the fact it takes several hours to recharge them is negative to me.

System minus batteries. I put a piece of cloth underneath so as not to damage the screen.

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I need to tidy this a bit now, which will only help further the screen rotation facility.

IMPROVEMENT:

Talking of such, I might consider if I can have that automatic switching when the screen rotates, which I talked about at the start of the project. I might have enough space now to experiment... :D :wink: I just need a bit over 1/4 of the space around the perspex above the PSone screen to accommodate this - I appear to have enough space now, it is a question of how reliable I can make it.

This is another challenge, just saves using switches, but a rather nice feature if I can make it work.

I need to make a semi-circle attachment with movable contacts which break one set of contacts (6) and resume with another set when the screen is rotated (6). I might use cotton ear buds for this wrapped in tin foil...keep looking at this thread to learn more... Image
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