Repurposing a click wheel

We think the click wheel is the biggest contributor to the success of the original iPods. The devices were a brick with a monochrome screen but the user interface was slick and easy to use. [Jason] decided he wanted to add a click wheel to his own project. After using a logic analyzer he discovered that it doesn’t implement a common protocol such as I2C, perhaps a deliberate move by Apple to keep the controller under wraps? He managed to get past this hurdle, as seen in the video after the break, by bit-banging the data in from the click wheel and then reverse engineering the protocol.

It’s connected to an AVR ATtiny88 with feedback shown on a character LCD screen. We’re glad that [Jason] tipped us off about this, but he doesn’t have any code available yet. We love to dive into the source so the sooner he gets it up the better! We’ve got an old 3rd generation with a bad board that is begging to have the wheel ripped out of it, not to mention the dirt-cheap replacements available on ebay.

24 thoughts on “Repurposing a click wheel

  1. This is a bit off topic, but has anyone tried to interface with the iPhone/touch digitizer? The idea that it can be multitouch is nice and I think (not sure) I read its connected via an internal USB interface. Course the connector looks like its hopelessly complex so it probably lacks the controller necessary to do something of that sort.

  2. @osgeld it looks like the whole housing is connected using just 4 wires for all four buttons, and the wheel functionality (from the video above). Assuming two of those are power and gnd, I’d say no — though this may be a different model.

  3. Wow, I pulled a click wheel from my old iPod 3G and was thinking of doing something like this, but I don’t have the hardware skills to do the protocol discovery…hopefully we’ll get some code :)

  4. Source code up now!!!!!!!

    sorry about the video quality on the screen. the camera didnt pick up good at any angle or contrast setting. i just dont think there is enough contrast on the screen for the camera to pick up well unfortunately.

    to therian:
    if i built the wheel myself i doubt it would come near the price, performance, packaging and power consumption that the clickwheel provides. though don’t get me wrong that would be cool!

  5. I have a 5G 30 GB iPod that was bitten by a dog, cracking the screen. It still worked for a while but eventually stopped. I had already planned to salvage the hard drive, but it’d be really neat if I could use the (somewhat marred) clickwheel for something too.

  6. to tiuk: theres a good chance that the 5G ipod is still running on the same protocol(physical and data). i have had my 5G open a few times and the connector was the same pin out iirc with the big difference of the clickwheel being integrated in to the plastic case of the 5G.

  7. FYI, the latest builds of Rockbox actually let you use the clickwheel of any supported iPod as an USB HID device. Certainly not of use to anyone wishing to use this in an embedded environment, but if you wanted to use an existing piece of hardware to control your media player or whatever, it works nicely.

  8. @garboui
    you perfectly right about practical point of using ready made parts, the results are better and it cost less.
    but in hobby purposes the idea thay project will ”live” (repeated) only as long as company exist sound depressing, or maybe it just me who want ”immortality” for circuits I spend time on

  9. @therian: Even in most hobby projects you depend on companies to some extent, and can’t always predict how long they’ll support the part you’re using. To some extent it’s inevitable, even if you use the most basic of components. Parts become obsolete, and you have to be quick/clever enough to find ways to overcome. I’m sure we can all name good chips and other components that were once readily available and commonly used by hobbyists, but aren’t anymore. I do agree, though, that it’s best to consider the availability of the parts you’re going to use. I think we’d all like immortality for the projects we work long and hard on. (Except those projects I did when first learning electronics. I made an awful lot of beginner mistakes, and hope those projects remain in their graves)


  10. @Inventorjack: Like the 4004? Back in the 1980’s the 4004 was a cheap and readily available chip at most of the ‘old boys’ electronics stores. Nowadays, 4004’s sell for hundreds of dollars on Ebay to various collectors for the crushed-velvet treatment. I am deathly afraid to try and use one of my few remaining 4004s in a project, for fear I will let the magic smoke out of what is now a 200+ dollar chip.

  11. @sasquatchking: I didn’t think it was a bad clip, except that he chose a poor angle to view the LCD from. I bit of explanation about what the project was and how it was done wouldn’t have hurt, though.

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