Can someone explain how this V-USB circuit works?

Hi everyone,

http://www.practicalarduino.com/pics/virtual-usb-keyboard-schematic.jpg

I'm attempting to learn how to communicate with Atmel chips such as the Attiny85 without having to use a serial-to-USB converter. I'm fairly new to electronics circuit design, and I am having trouble understanding what role the zener diodes and resistors have in the communication between the 5V MCU and USB. If you can, please explain why certain resistances and zener diode ratings are used in this situation(and why zener diodes work and regular diodes don't)

Thanks in advance,

Tom

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mcb1 over 11 years ago

I suggest you head over to the Digispark forums.
They use this method and Bluebie has some very good explanations of it.

There are also some explanations of programming raw chips.

Mark
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mcb1 over 11 years ago

I suggest you head over to the Digispark forums.
They use this method and Bluebie has some very good explanations of it.

There are also some explanations of programming raw chips.

Mark
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