For the idea to program an AVR via keyboard LEDs I now implemented some 
piece of software.
I plan/would like to extend platforms to windows and graphical linux.

At the moment it just supports framebuffer terminals of linux.
It is slowly, it is tested, it works, and it should solve 
chicken-egg-issue for most people satisfactory?


As physical layer the keyboard LEDs are used:
 *   SS/CS (chip select)  :  SCROLL LOCK LED
 *   MOSI      :  CAPS LOCK LED
 *   CLOCK      :  NUM LOCK LED

As input deals any key pressed: (use a optocoupler?)
 *   MISO == 1  <=>  any regular key pressed
 * (  MISO == 0  <=>  NO key pressed    )

(You can increase the speed if you omit MISO)


Useful comments are appreciated.

Best regards,
  Stephan

Hi again.

For everybody who might be interested: The software now does support 
Microsoft Windows, too.

http://matrixstorm.com/avr/tinyusbboard/bootloader/keyboardasp_v1.zip

I hope to get some feedback.
Useful comments always are appreciated.


Best regards,
  Stephan