Random USB caps locker


This is one of the most original April fools gags I’ve seen. [Garrett] sent in his USB caps locker. It’s built from an ATTiny45 and puts out an intermittent signal to set the caps lock key. Considering what day it is, it appears to be legit. After you’re done screwing with your co-worker for the day, you might be even more interested in the easylogger project that it’s based on.

20 thoughts on “Random USB caps locker

  1. I love it! How does one make the Attiny show up as an HID device though? I suppose google is my friend, and I’ll go look now!

  2. thanks…it was really a spur of the moment thing, as you can see by the messy construction. but really easy to put together. obdev’s avr-usb works great. it only took a little while to dig into the easylogger code and disable the adc and button detection parts, randomize the timing, and have it only send scancode 57 (caps lock). if you want to do something similar, just make sure a report with keystroke is followed by an empty report. i thought of a few other interesting variations, trying to keep focus on “harmless” stuff. sending a “volume up” keypress is easy…could be quite effective. holding down shift for a while would be more subtle than caps lock. how about pressing “F1″ every couple minutes to be extra helpful. mouse wiggles can have bad consequences, but should be highly entertaining on a gaming machine. wheel of death: mouse right at high speed, click mouse1 button at 10hz and roll mouse wheel for weapon select. anyway i’ll put some schematics and pcb and code up later for those of you who want to try this. the eagle part for the board-edge USB connector could be handy too, i’ll make it available.

  3. All it needs is a radio frequency receiver for the trickster to trigger on and off at the appropriate moment if in a group of computer uses.

  4. ryan:
    If its a proper usb 1.1 client, that would mean you would have have to take up one of the ports. Or, the alternative is you jam a second usb hub inside the first, but then your wasting 3 ports.

    It can be done though. You could even put a hub inside the keyboard itself, along with this thing, so that they would never figure out what was going on.

  5. That is great, you need a USB header version for inside the case, possibly mounted on a CD-Rom audio cable.

    They would never find it, you could tuck it anywhere.

  6. an even sneakier variation would use a 5 pin jack with the same layout as most spare USB pin headers on motherboards. putting in inside anything other than the computer itself means that replacing that part would solve the problem. however it still means taking apart the computer. using the tssop or mlf version of the attiny45, and a double sided pcb, it should be possible to put the whole circuit on the opposite side of the pcb from the contact strips. glue on hollowed plastic spacer or cast on some epoxy, and you have a little device that fits entirely inside the usb jack.

  7. This makes me really happy! I use AVRs in my projects all the time and i’ve been wanting to add USB support to projects! The linked easylogger projects looks like the perfect starting place, thanks Hack a Day! :)
    -Taylor

  8. @10
    If you’re going to put it in a keyboard, why not just have it short the “caps lock” key every so often, instead of dealing with the USB interface?

  9. @13: perhaps to prevent ppl trying a different keyboard.

    I guess with this, you would see the caps lock light blink. Or it could be pulsed.
    It could make it so that it stops bugging when you press the scroll lock key and then say there is no problem :)
    (The 3 lights will propagate to other keyboard devices)

  10. This inspired me to write a software version. I wrote an app that randomly (30% of the time) toggles caps lock when you press left shift. I figured that way it would be extra annoying because people would think they miss clicked. Anyways, you can get the app at my site officewarfare.net.

  11. I’ll take half a dozen if it’s under $20 each.

    This is just too good not to get several to play with.

    Alt+TAB
    Alt+F8
    and the Terets version could be a real riot.

    I Love it.

    will be looking for these on e-bay.

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