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

[bacteria]

Only had to solder one wire from the mains in plug to the switch and system works fine, irrespective of the overclocking of the GP2x. Nice.

Not all games on the GP2x run totally great on TV-out, you can get some flickering on some programs depending on which library the program was compiled with and whether it is good for TV-out; however the major emulators like MAME, MegaDrive, NeoGeo work fine; GBA loses some of the screen area; otherwise fine, not tested other emulators out yet.

Just had a play on my system for a while, like it. The screen rotation is smooth and works great too. For some reason it rotates perfectly smoothly when the unit is upside down, sticks a bit when done from the front. I will but in some struts to stop any bending of the top and bottom case, that will solve that.

Happy so far!

Back to modding on Monday...

[dragonhead]

i see another alternative, tho slightly costly. go for lithium ion batteries.

something like this http://www.batteryspace.com/index.asp?P ... rodID=2230

7200mAh is a bit of an improvement over the 4200 you had before. get a charger as well and you should be set. it has a protection circuit built in so it wont grenade on you.

[bacteria]

dragonhead - When I looked for batteries at the start of this project I looked at this company but they were very expensive to the UK.

The cells I had used were 5500mAh not 4200mAh, and photo grade quality, yet I only got just over an hour before the voltage dropped below the PSone's operating voltage. I guess therefore that 7200mAh would only last for about, what, an hour and three quarters? (poor).

I get the impression that the only way to run the power hungry GP2x with a PSone screen is to run sets of cells in parallel, preferably three sets; or just use mains.

I have one of the Li-ions as per below, but the 4650mAh version which I got very cheaply on e-bay, although I don't have a charger for it. They are a wee bit thick at 38mm http://www.payless-batteries.co.uk/camc ... er_Battery

Even with two of these and a charger I am looking at about £80 ($160) which is a lot of money for a project.

My system at the moment, PSone screen and mobo, wiring, perspex casing, hot glue, controls, etc come in at about 750g, when finished it will weigh about 800g. Add to that batteries, the 6 x C cells weighed 500g, or 18 x AA cells weigh 500g (3 x 6 cells in parallel), or 2 x the Sony Li-ions at 580g. This means in terms of weight that all three examples are ok for weight - 1.3kg is fine to hold, but you don't want it much heavier.

I have about 26 x 2650mAh / 2700mAh AA cells available, so I could rig up 3 sets of 6 cells in parallel and see how they fare, just out of interest.

[dragonhead]

dragonhead - When I looked for batteries at the start of this project I looked at this company but they were very expensive to the UK.

The cells I had used were 5500mAh not 4200mAh, and photo grade quality, yet I only got just over an hour before the voltage dropped below the PSone's operating voltage. I guess therefore that 7200mAh would only last for about, what, an hour and three quarters? (poor).

I get the impression that the only way to run the power hungry GP2x with a PSone screen is to run sets of cells in parallel, preferably three sets; or just use mains.

I have one of the Li-ions as per below, but the 4650mAh version which I got very cheaply on e-bay, although I don't have a charger for it. They are a wee bit thick at 38mm http://www.payless-batteries.co.uk/camc ... er_Battery

Even with two of these and a charger I am looking at about £80 ($160) which is a lot of money for a project.

My system at the moment, PSone screen and mobo, wiring, perspex casing, hot glue, controls, etc come in at about 750g, when finished it will weigh about 800g. Add to that batteries, the 6 x C cells weighed 500g, or 18 x AA cells weigh 500g (3 x 6 cells in parallel), or 2 x the Sony Li-ions at 580g. This means in terms of weight that all three examples are ok for weight - 1.3kg is fine to hold, but you don't want it much heavier.

I have about 26 x 2650mAh / 2700mAh AA cells available, so I could rig up 3 sets of 6 cells in parallel and see how they fare, just out of interest.

you do know you have to cycle through a few charges with NIMH batteries before you get their full capacity right? you need to charge and discharge them 5 or 6 times. the first few charges only get about 1/2 their full capacity.

[bacteria]

I had charged them twice from new before trying them; first time from new but their voltage dropped to about 7.6v after a week or so, so I recharged them before using them. NiMH cells lose voltage after being charged quite quickly (the C cells dropped from about 8.4v to 7.6v after only a few days, without use. Problem as I mentioned is that the GP2x drains battery life; so it doesn't take long before the screen wobbles from lack of voltage soon after recharge (just over an hour) and if left for a few days and the voltage drops anyway, doesn't leave enough voltage for the screen to work as the voltage then takes a tumble when the GP2x is working via the Ti card.

Basically, NiMH cells don't seem useful for a PSone and GP2x project, unless in parallel, ideally 3 sets I imagine. Li-ion seem a better idea, but their outlay is expensive, especially when you don't know how much better they are until you buy them and try them on a high drain application. You also have the issue of the weight of them, and trying to keep the system reasonably well balanced - if the weight is all at the bottom there is a tendancy for the screen to be striaght which doesn't give good viewing angle, and if top heavy will be heavy on the hands. I think, taking all into account, I am best staying with mains power, it is reliable. I might test to see how 3 x 6 AA's cells fare, out of interest, but may not bother. I rather think even this might only give about 3 hours use!

[ShockSlayer]

I dont really know what choices you have made, but if you were worried about too much voltage going into the PSOS then couldnt you have just put on a 7805((((EDIT: I meant 7808!)))) for when the voltage spikes?

Or atleast, thats what I did for my XS64

SS

[vskid]

If you look at voltage graphs for NiMH's (just Google it if you want to see), they usually start at 1.4v, then by about 25% into the discharge its dropped to 1.2v, which holds fairly steady until its nearly discharged. So the 8.4v is pretty just a bit of overflow that discharges on its own fairly fast. As far as I know, no one else thats used NiMH batteries have had the same problem. You probably need to do a couple more discharge cycles (maybe discharge them all the way instead of just til the screen dies) or it could be that your unmodded screen draws too much power, which I'm kinda doubting since the N64 in N64p's draws more power than an unmodded screen.

[bacteria]

vskid - the main issue here is the voltage drop when the GP2x is on against when it is off. The cells were at about 7.7v when not running anything, 7.7v when just running the PSone screen, but about 6.5v roughly when the GP2x was on. The screen needs more than 6.5v to run - they audio amp works but the screen doesn't. Judging by this, I would need perhaps 8 cells providing initially 12v after full charge, to reduce to about 9.6v after normal discharge and about 8-8.2v with the GP2x on; this is getting daft and has further problems associated. The other solution is to have 1 set of C-cells purely for the PSone screen and 3 sets of AA's (3 x 2 batteries) for the GP2x to give about the same life as each other; which means two recharges and one set will run out at the same time and more weight and a bigger case. The fact the GP2x drains photo grade 2700NiMH AA cells in about an hour or less many times, overclocked GP2x, and did the same with my 6 C cells (with screen too), would indicate the GP2x when overclocked, must be drawing something like 2 amps - 2.3 amps or thereabouts, plus the 750mAh or so for the PSone screen; if this is the case, I will not get good playtime unless I have at least 16amps from battery packs (eg 3 Li-ions in my previous posting at about 20 amps), which is rather expensive and heavy - about 1.5kg for the batteries, 1.3kg for the rest of the system = far too heavy.

I think for this system NiMH cells are not good enough, you might be lucky and get 2 hours playtime, which frankly is not worth the effort. The choices are Li-ion packs (2 or 3 in series) or mains powered for this application. The PSone cable is rated at 3 amps and works fine. I feel I will have to stay mains powered. It is far cheaper, reliable, less hassle, cost effective and light. I am always near mains power anyway! (at least I proved the system working on batteries though).

[arfink]

Well, mains is where everything comes from anyways, so why not use it? BTW, very nice project here, it's coming along very well. I just fried my second NOAC today (stupid 7805 blew up, fried my board!) So yeah, I know all about batteries being bad. Fortunately I don't need a boatload of power for mine, so I should be OK. I like the rotating screen idea, it seems very sell thought out. If I ever got a GP2x, I think I'd probably just leave it alone and play it as-is. Of course, now I want one of the F-200 which has a real D-Pad now instead of that joystick.

[bacteria]

Personally I think a GP2x with a touchscreen will be even more awkward to use than normal. When I play DS games I prefer the ones not needing to use a pen on the touchscreen (finger is ok) as I find it a pain.

Wait until the Pandora comes out (www.gp32x.com forum) as either you might find it better, or buy a cheap F200 when others buy the Pandora and sell their old models. I like the GP2x, it isn't perfect and has its problems, but plays a good selection of emulators very well and full speed; like MAME, NeoGeo and MegaDrive for example. If you aren't fussed about touchscreen, get a MKII GP2x (as I use).

[bacteria]

OK, project:

I have little time today remaining, but time enough to provide details of the mechanics of the switch facility for the screen rotation.

The screen rotates 90 degrees from landscape to portrait mode, so I need to have 1/4 of the space on the perspex circle inside the case, above the PSone mobo. I have this space now as the batteries are removed for reasons discussed before.

I only need to complete a circuit, so need something which can touch something else to complete the connection, yet not be stiff to turn and have a margin of flexibility. This is why I will make it with cotton ear buds covered in tin foil - the ear buds are a bit flexible and the cotton makes it have "give", the tin foil is a good conductor for signals (not power); so I only need to have a tin foil covered ear bud rotate (breaking contact 1 for landscape mode) and make contact with contact 2 (portrait mode) and back again as needed. Simple, cheap and easy!

Buds and foil:



Yellow lines illustrate the rough positions of each bud and the orange surround illustrates the part which ensures the cotton buds travel unhindered.



Crude pic of some buds in place, I will shorten them of course! This is just illustration.

I know this process will work, it just needs a couple of hours making, hot glue, card and some wires to solder. You can't solder to tin foil of course, but it is easy to wrap some around a wire for contact. I have made things like this before (hence Blue Peter logo in my sig).

[bacteria]

Making the auto-switches:

The idea here is to make contacts which will change depending on whether the screen is portrait or landscape. I need 4 for the directions for the D-pad and one for the A button and one for the B button (instead of Vol+ and Vol-).

I started by cutting 3 cotton ear buds in half, using UHU glue (general purpose glue) on the cotton, then wrapping some tin foil over it. I stripped about 1cm from the wire, and swapped it around the cotton bud stick.



Using a compass, I drafted a semi circle onto mounting board which was about 5mm or so bigger than the perspex circle on top of the PSone mobo. To secure the top and bottom layer, I popped in the finished cotton buds and then hot glued some struts to the perimeter.



I then wrapped strips of tin foil under and over the top piece of card, sticking it to the surfaces with UHU glue. Afterwards, a wire was stripped and the bare wire put between a small piece of electrical tape and the tin foil to make connection to the tin foil.



All six done, some bare wire left to solder wires to, surrounding areas of wire and foil hot glued to keep it in place.



Put construction in case, starting to get all 6 sticks hot glued to perspex. When these are all in place, I can rotate the screen and know where the contacts need to go for the rotation.



When done, the construction will be secured to the case, so it stays in place whilst the cotton buds rotate on the screen.

All six attached, and all work (tested by multimeter).



...and their corresponding spaces are mapped for their connections.



The foil covering the cotton bud is uneven on purpose as it only needs to touch the foil on the other connection anywhere (even a single spot) and contact is made. As this is mechanical and liable to some degree of tolerance, I decided to put some foil on the underside of the contacts. This eliminates the chance that some contacts are made and others not, the bud will have no choice but to make contact with the top, or bottom, or both contacts.

Run out of time now, more time tomorrow. Secured tin foil to other side inside, pics below. Tomorrow I will get the other side finished and secured to the case itself.

[bacteria]

Finished the assembly. All contacts work, checked with multimeter. All the bare wire strands have been tinned ready to solder to.

The light pink arrow is a small assembly I made on top of the perspex circle to act as a "stop" so the screen can only rotate in the right direction and only the 90 degrees it needs to. The darker pink arrows are the plastic "stops" I made.

Works fine, I do however need to tighten the movement of the outer plastic circle on the case so it doesn't have the same play as now, it can make the difference between everything working perfectly and only most of the time.

You can see both modes of screen rotation below:






End of project for today, made good progress!

I put in some more posts to secure the construction I made earlier, and changed the D-pad cross from the black one to a silver one (painted from a previous project, when I had wanted to put one on the PDA).

The screen is presently in its rotated (portrait) state, when the screen is in its normal position and the cotton buds are in the lower position, that is the landscape mode.

I have connected the wires from the D-pad to the cotton buds; and connected two sets of wires from the GP2x accordingly - left (landscape)=down (portrait), right (landscape)=up (portrait). After securing each wire, I am hot gluing it in place. You may notice I have labeled the wiring on the semi-circle, so I know what is what if I need to open the case up at a later stage.



I just need to finish the last four sets of wires, and all done. I can then remove the three switches I had been using before, I intend to replace them with two tact switches for the GP2x volume controls - on this project I need volume controls for both the PSone and GP2x. Assuming the testing afterwards comes up trumps, I will be able to move to the next step.

[bacteria]

I spent a few hours this morning tidying the wiring and moving some of it about. I wired some of the contacts on my cotton buds wrongly, all corrected now. The screen rotation works great and the contacts are reliable and work very well indeed. I tested (in "T-Mode") all the buttons on the GP2x, all fine.

Tomorrow (Friday afternoon) I will be working on the rounded corners, get rid of any "sticky" bits remaining on the rotation, where the outer circle touches the inner one (small amount of dremelling wil fix this), then I can start the casing!!

[khaag]

Let me just say that your are one INNOVATIVE son of a gun! These inventions and solutions to problems you keep coming up with just floor me! Who would have thought to incorporate Q-tips and aluminum foil into a complex project like this?! You're project is coming along very nicely bacteria! I can't wait to see the final product.

If its not too much to ask, any chance of you uploading a quick video of the screen rotation in action and it switching from landscape/portrait mode?