Inexpensive USB Keyboard

September 9, 2010

I had done some work recently to show that a quick and easy USB keyboard could be created created with the teensy and found it to be a 1 day project that was easy to implement. There was one problem with this solution, the cost. It was very pricey for something as simple as a USB keyboard. I wanted to keep some of the nice processor functionality so a dumb terminal that translated into USB would not quite cut it.

I stuck with AVR in this case and took a look at v-usb which lets you create simple HID Keyboards and a large number of other projects quickly and easily. The good news is you can do it on small cheap hardware that is still extremely powerful. I choose the attiny85-20pu as my processor going over the 4-key keyboard schematic and found it to be perfect for what I was looking to do. Here is the part list and pricing:

  • ATTiny85-20pu – $1.80 from Mouser
  • 2x 68 ohm resistors – $0.30
  • 1x 1.5k resistor – $0.15
  • 2x 1N4148 Diode – $0.04
  • 1 ended USB type-A cable – $2.10
  • 1x 0.1uF ceramic capacitor – $0.30

Total: $4.69

The same using the teensy was about $32. While the teensy is of course a more powerful device, it all depends on what you intend to do with it.

I will post more later with the rest of the details on the project as it gets finished. I have some boards to etch and some molds to resin.


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