Introduction: SD/MMC Fits in Floppy Edge-connector

Picture of SD/MMC Fits in Floppy Edge-connector

You can attach an SD camera memory card to any homebrew DIY project that has a few I/O pins,
using ordinary connectors you probably have right now.

For more details, how to obtain free mmc device drivers, and installing various open source Linux distros on WRT54G wireless routers (and other routers and devices), go here:

This is the finished "SD floppy" connector, which has been running flawlessly inside a friend's wireless router for 6 months now:

Step 1: 01_floppy_cable.jpg

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Here is the standard PC floppy cable we will use for this hardware hack, with an SD card for a size comparison.

Step 2: 02_5.25in_floppy_connector.jpg

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Here is a closeup of the 5.25 1.2 MB floppy edge connector. You can see the pin numbers (we use the even pins) in this photo.

Step 3: 03_good_pin_alignment.jpg

Picture of 03_good_pin_alignment.jpg

I tried a lot of different connectors I had laying around to find one that could be used as an SD card socket. Here a floppy edge connector is being tested for SD card fit and alignment. You can see how well the (partially inserted) SD card pins align in the floppy connector. You can see the upper connector pins reflecting from the SD card pin pads.

Also, you can see that the ridge on the edge of the SD card slides firmly into the groove in the connector plastic pin separator, which aids card alignment (when the card is inserted using the connector even pins).

It causes no harm to insert the SD card backward, because the odd pins are not used in this application.

Step 4: 04_fully_inserted.jpg

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Here is a front view of the SD card, fully inserted into the floppy edge-connector. Be sure to firmly insert the card until it is all the way in.

Step 5: 05_new_sd_cable.jpg

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Here is a photo of the ribbon cable already soldered into the wireless router, with the wires spread and pressed partially into the backs of the connector pins.

For more details on where to connect the wires inside your wireless router, detailed links are provided at the bottom of this page:

A closeup of the connector at this point can be seen in the next photo.

Step 6: 06_wire_even_pins.jpg

Picture of 06_wire_even_pins.jpg

Here is a closeup of a piece ribbon cable I "peeled off" from a scrapped 25-pin serial cable. You can use part of the floppy cable if you wish.

You can see that I have carefully removed the back of the connector (by lifting the spring-loaded side clips with a small screwdriver), and pulled off the old ribbon cable.

If you accidentally bend any of the connector pins, straighten them with a small needle-nose pliers before continuing.

Spread the wires back enough to fit the connector, then push them down between the odd-numbered pins, and push them into the even numbered pins (as shown in the photo) using a small screwdriver. When inserting the wires, note that the pins on the small side of the plastic connector edge guide separator are not used in this application. You do not need to push the wires all the way in, because that will be done when the connector back is squeezed on later.

Step 7: 07_squeeze_together.jpg

Picture of 07_squeeze_together.jpg

Now we snap the connector back onto the connector. Then we squeeze the connector on firmly with a vise, C-clamp, vise-grips(TM), or whatever. I have even carfully used a hammer to gently tap the connector backs in place, but I much prefer a tool that applies firm even pressure, as I did for this photo.

Step 8: 08_label_and_guide_shim.jpg

Picture of 08_label_and_guide_shim.jpg

Here is the completed SD floppy connector, with label attached showing which way to insert the SD card, and with a guide shim (cut from a plastic soda pop bottle) folded over and inserted to help guide the SD card into the proper pins.

It works!

For more details, how to obtain free mmc device drivers, and installing various open source Linux distros on WRT54G wireless routers (and other routers and devices), go here:


Alquimista (author)2014-04-06

could replace the floppy disck from the Apple with this card?

als_liahona (author)2009-11-17

Brilliant idea!  I just added a comment in my Instructable (Great idea, great Instructable!  I just added a comment to my own Instructable ( recommending this as an alternative to the expensive SD Card breakout board I used!) suggesting this as a possible, lower-cost alternative to the SD Card breakout board I used.  I'll be trying this out for future projects!

VirtualBoxer (author)als_liahona2012-12-16

I never saw that kind of joke before, but I understand it.

VirtualBoxer (author)2012-12-16

I had guessed that it would fit, but I didn't assume that it would actually make a connection.

dognose (author)2007-03-11

Would this work with USB?

VirtualBoxer (author)dognose2012-12-16

An Arduino Due might come in handy here. It runs at 3V3 and has hardware USB. However, I don't know exactly how, but it could be done. Maybe I should start trying once I receive my Arduino Due.

d1ndian (author)2008-03-14

hi was a floppy drive cable right?.........aaaaaaa.........what about if i use a cd drive cable............hhhhhhhhhhhhhhhhhh

Derin (author)d1ndian2008-06-12

wont work cd drives use holes as in the left pic floppy connectors(5.25" size)use the suitable connection (right picture)and 3.14 drives use the center connector(admire the smaller number of pins)i cant put up pics now

VirtualBoxer (author)Derin2012-12-13

You can't because IDE doesn't have edge connectors.

Popcornfilms (author)d1ndian2008-10-06

you sir. are a cool dude. such wise observations!

matstermind (author)2010-05-11

could this be used to add more memory to an arduino?

skaar (author)matstermind2011-10-08

yah, old post, but... you'd need to have the filesystem driver to use it.

anilmosses (author)2011-04-02

It's very good

rogerjowett (author)2009-12-16

isnt there a floppy disc that has the sd memory device inside it
can you read and write data
what kind of read write speeds are available please?
does it need a driver?
can you modify zx microdrive cartridge for sd/compact flash also
is it possible to use the motor to power the device/charge any battery required?
what transfer speeds possible from 8 devices?

d1ndian (author)2008-03-12

hi nice trick but what does it realy for ....Ooo i understand........well what about if we attach a usb cable on the end of that cord.........well what's your opinion...................byyyyyeeeeee

DBLinuxLover (author)d1ndian2008-09-30

well uhm. This is primarily designed for the hack of the Linksys router WRT54G, which allows you to attach an SD card, and have the router interface with it. Then you can run the router with that extra memory. (You could host email server, web server, etc off your router). No usb support. Want a USB connection? you would have to buy one.

jamwaffles (author)DBLinuxLover2009-03-04

He he i steal internet off one of those routers :P. Dont live near cambridge do you?

carlos-felo (author)2009-03-04

It's very great!

cuchulain92 (author)2008-12-26

Here's the idea I've got- need to find out if it would work. Use the SD card as the boot drive for Linux, and add it in place of my floppy drive on a desktop: a fast boot, low access time for the OS, less moving parts & less space...

khromes (author)2007-05-08

i was wondering if this could be used with an old laptop, i'm buying a compaq lte5300{manufactured 1997}, and it has no usb or cd-rom. i would like to know if it is possible to replace the laptop's floppy drive with a SD card? maybe then i could use the SD as its removable storage, would be nice to use a 2gb card, sure beats any floppy disk!

mycroftxxx (author)khromes2008-05-06

The basic answer to this is "No", the technical answer is "kinda". This instructable is about using the floppy cable connector as a cheap and probably-around-the-house-somewhere SD card socket, for people who are planning to add a socket to an existing piece of hardware but don't feel like ordering one from a supplier. This cable is meant to be attached to a serial port so that it can be accessed once the firmware of the device (in this case, a wireless router) has been modified. You _can_ do the same thing with your old laptop, but there are better tricks you can try.

twenglish1 (author)2008-03-01

how would you hook a usb connector to this??

DieCastoms (author)2007-05-26

I did not read the replies so this may already have been said, why not tie the odd pins in the correct order to the even pins so that if you push the SD card in 'upside down' it will do the same thing anyway? Awesome idea by the way, might be useful to me in the future. Mike at DC

dognose (author)2007-03-11

Or maybe a dual channel one that could be used like a dual tape deck to make copies.

robwen (author)dognose2007-03-11

The current mmc driver uses SPI protocol, which requires a separate CS (chip select) wire for each SD card. I have some code that I want to add to the driver that support full MMC protocol, which does not need any CS wires, but instead uses a card addressing scheme that only uses the clock and data wires, and also supports many SD cards attached in parallel to the same wires.

My thoughts when I first did this hack were that I want two SD card slots on my router -- one to "boot" the router, and another to plug in SD camera cards. I currently have a CGI script on my router that when viewed in a web browser scans the SD card for /DCIM/* direcories (created by digital cameras), and building a webpage of image thumbnails which may be clicked to view the larger image.

Alternately, the second SD slot could also be used to copy SD cards...

P.S. This does not use USB. Some routers have a USB port and could use a USB thumbdrive instead of an SD card.

!Andrew_Modder! (author)2007-02-05

I see your using the "skuzzie" side. I wonder if it works with normal side?

bostrees (author)2006-11-06

Now... Maybe I'm just not thinking this through all the way, but is there a way to do this or something very similar and have it connect to a motherboard via the floppy connector or is this specifically for attaching to the wireless router?

bostrees (author)bostrees2006-11-08

I look forward to that one then :D I don't have anything reliable to solder with right now and unless I can find a few other projects, I'm not about to run out and get something for one project :P

robwen (author)bostrees2006-11-06

This lets you connect an SD card to any device with a few spare I/O pins. I plan to wire one up to a parallel port connector when I get some free time. For more details, read the text at the website link.
There is more stuff too, at

Myself (author)2006-09-23

Nice photos too, good closeups with nice even lighting. Just when I was considering throwing out my bucket of old floppy cables, someone finds a new use for edge-card connectors! I find it ironic that the connector outweighs the card it's connecting to. If you remember how big the old "full-height" floppy drives were, it's just breathtaking.

trebuchet03 (author)2006-09-15

awesome -- I saw this on hackaday not long ago... excellent work

billcd (author)2006-09-15

Very cool. Those are my favorite routers. I've got 3 of them. A set of batteries and they will go anyware and do anything! And now with more memory!

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