USB Caps Locker

General discussions about V-USB, our firmware-only implementation of a low speed USB device on Atmel's AVR microcontrollers
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USB Caps Locker

Post by highwayman » Sat Mar 14, 2015 9:20 pm

So.... I have wanted to make this project for a while:
And April 1 is approaching. I made some boards with the ATTiny 85, resistors, capacitor, no zener, no crystal. I flashed the hex into the chip. Plug it into a USB port.

USB Device not recognized
Device Status: Windows has stopped this device because it has reported problems. (Code 43)

It shows as an Unknown Device. Do I need specific drivers (that can be installed quickly)? Are there certain fuse settings? I think that I read somewhere about setting the fuses for the PLL of the ATTiny85?

Any further assistance would be greatly appreciated.

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Re: USB Caps Locker

Post by blargg » Sun Mar 15, 2015 9:52 am

Correct me if I'm wrong, but doesn't this put 5V signals over the USB data lines? I don't see anything to drop the +5V from USB that powers the '85 I wouldn't connect this to anything I cared about. I'm amazed that the author of this project would remove the zener diodes just to save a few components (as stated on the page), while making it violate the USB spec and possibly damage the USB port.


Re: USB Caps Locker

Post by Guest » Mon Mar 16, 2015 2:24 am

Good call blargg!

Restarted a new project ( with ATTiny2313). Able to install the hardware driver and communicate with the 2313 when it was powered at 3.3V. Same set-up gives "USB Device not recognized" when powered at 5V.


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USB Caps Locker with 3.5V

Post by horo » Mon Mar 16, 2015 4:24 pm


Another solution would be to cut the connection to USB pin 1 (Vcc) and insert either a red SMD LED or two normal SMD diodes in series to drop the voltage from 5V down to about 3.5V - that's close enough to the 3.3V from the specs. I never had problems with the two-diodes-solution.

Ciao, Martin

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