I had been trying to extend the SD card cable for a remote one for my GBA M3 Flashcard for my N64/GBA portable project. It didn't work on this but works fine on a PC and also the GP2x.

(This is Psycho Pinball on the MegaDrive (PicoDrive emulator), in case you were wondering what the game is)



Close-ups:





This would be handy if you want, for example, to make a mini cabinet and need to relocate the SD card slot.

Have a look if you are interested at the pinout, etc - page 20 of my WIP. I originally designed the pinout to convert between a Mini SD card and SD card; however this is also the case for the Mini SD adapter I used (male > female, for want of better expression).

Link on BenHeck

Once the software is released to give true 320 x 240 pixels on the tv out of the GP2x, and I have finished my N64/GBA portable, I intend to make a nice big GP2x, 5" PSone screen, S-video, longer life batteries, better controls and better spaced, D-pad AND joystick (some games benefit from D-pad, others by joystick) and better speakers.

Anyway, I thought you guys might be interested to see how to relocate an SD card if you want to do this on your GP2x.

Nice work!

Have you tried IDC cable for the hardware you extension doesn't work on? That may be more reliable.

Oh, and don't forget that SD cards can run at anything upto 50Mhz (although 25Mhz is far more common). So take the appropriate precautions.

by precautions would you mean shielding ?
im a bit confused.

What is IDC cable please? I tried the thin, separate IDE cable (as per pic) then tried thicker electrical cable; same result. Works in PC and GP2x but not GBA. Any ideas?

Please elaborate - precautions? (apart from using electrical tape, of course!)?

IDC is the type of cable used in IDE and floppy drive cables, more commonly called ribbon cable. It's designed for higher transfer rates. The configuration is usually data, common, data, common, data, common etc to prevent leakage of data from cable to cable by placing a common (ground) between the data cables.

Here's some multicoloured cable:

As you can see, individual cables can easily be split away from the ribbon allowing easy soldering!

Ah, that's the cable I have been using anyway.



It is useful stuff!

(an early project pic)

That looks like loads of twisted pairs, which is for differential signaling.

You need ribbon cable that's still in a flat ribbon for most of its length with every other wire grounded.

by precautions I mean what has really already been stated - the wires you are extending can be running at upto 4-bit parallel 50mhz. If your wires are not correctly insulated or are too long, it can introduce cross-talk and capacitance. Both cause corrupt data (eg. see http://en.wikipedia.org/wiki/Slew_rate )

Either wrap each data wire with a ground wire in a twisted pair fashion, or use IDC cable in the way WarmFluffyUK has pictured (Do not seperate the wires and let them run as flat as possible)

Whichever way you choose, keep them as short as practical and keep them all the same length.

Er no, like Squidge and Firefox said earlier, that cable shouldn't be used. Just to clarify, here's another pic of IDC cable, this one has connectors on it already:

Interesting, thanks for the feedback.

On my N64/GBA project I started with the ribbon cables but found if I separated the wires it was too easy to break the single strand of wire inside (a slight tug and you could hear the wire snap). They were also too rigid. I then used the strands from a couple of IDE cables (as per pic) on my project; I have used the equivalent of several meters of the stuff in my project and it all works perfectly, however of course I couldn't use it for carrying power as there was too much resistance (I did try it, it worked the N64 system but took a few reboots each time - I changed the wires for proper electrical wires and it is perfect every time now). The wires I use however work absolutely fine for cart slot relocation, remote controller buttons, joystick, D-pad, controller system, controller power, N64 memory card wiring, general data and switching (if it didn't my project wouldn't work, as all the above are needed to get the system working).

However, it may well be that I need to use proper ribbon cables for SD card extending, so I will try the ribbon cable you suggested, I have some lying about doing nothing. If it makes it work on my SD card slot on my GBA M3 Flashcard, I will be most grateful for your assistance! I will use alternating wires in the ribbon cable as you suggest. If this doesn't work, probably nothing will now.

I hadn't appreciated before that data wires in ribbon cables are sandwiched between common wires. Interesting.

I will let you know the result. Just warming up the soldering iron at the moment....

Thanks again.

Ok, tried it, made no difference. This probably isn't that surprising though, the strand cables I used before are thicker than the ribbon cable wires (both types are IDE cables). I then tried it with electrical wires, same result. I have now tried it with ribbon cable, using alternate wires, same result - still works on GP2x but fails on GBA M3 Flashcard. Total wiring length I tried (and need) is only 25cms long.

Never mind, I know I have tried all the alternatives now. Thanks for the suggestions guys, appreciated.

Did you connect the "gap" wires to ground, though? That's an important step.

No, I haven't; interesting comment.



You mean pin 4 on the diagram - wire one side of each of the adjacent wires to this one ground contact? If this is what you mean, I can easily try it, nothing to lose! If your assistance proves to provide the solution, I will give you a special mention in my BenHeck thread!!

Why would the same extender work on the PC and GP2x but not on the GBA flashcard; rather than nothing at all? Seems strange.

I have had to keep about 2cm of the old wire on the original contacts, as I need flexibility on the SD slot on one end (otherwise the contacts break) and I need it on the flashcard side as otherwise the cart won't go into the GBA; the rest of the wiring is with ribbon cable.

This is what I love about forums, the sharing of knowledge and community spirit.

That's the one! On the system end of the cable, connect the gap wires to the GND pin. (I don't think it would be a good idea to connect them at the card end as well, otherwise you'd have earth loops.)

That's why it's important to plug the blue end of an IDE cable into the motherboard; so every other wire in the ribbon is connected to the motherboard's ground.

I have rendered a little diagram to show how to use the commons:



It's not physically accurate, it just shows the configuration.

Nice diagram, lets hope he gets it this time

Squidge - Yes, I have got it! (cheeky!).

WarmFluffyUK - lovely rendering skills! Wonderful!

Firefox - Many thanks!

Thanks guys for your feedback, appreciated.

Heating soldering iron up again....

Did it exactly as suggested....checked each contact with multimeter first (and all grounds ok)...all ok...booted up again...no difference whatsoever - "card not formatted..." - put SD card back in its slot on the flashcard (no extension), all ok again! Aargh!!

sounds like you need a 'scope to ensure the edges of the signals are not being rounded by your extension.

I don't have one, don't know how to use one and wouldn't know how to stop "signals being rounded". Apart from that, great!