random notes on the AT90USB...

Bootloader

I have an AT90USBkey with the DFU bootloader.

• ​http://sourceforge.net/projects/dfu-programmer/files/ is the right tool to flash it (Debian package available).
• Run on 5V power supply : ​http://www.newae.com/tiki-view_blog_post.php?postId=9 . Good to know : the bootloader will detect the supply voltage with the voltage sense resistor, and enable the USB regulator as needed.

Reserved pins

On the dev board :

• PF0 = tempertature sensor. May or may not be a problem.
• PF3 = resistors to sense power supply.
• PE0/PE1 = on board flash chip select
• PE2 = HWB button.
• PD7..4 = LEDs
• PB7..5 and PE5/4 = Joystick

Leaves us with :

• PA 0..7
• PB 0..4
• PC 0..7
• PD 0..3
• PE 6..7
• PF 1,2,4..7

33 free I/O pins. Some more can be used in some cases.