Friday, August 17, 2007

PS/2 Keyboard startup

I've been adding a ps2 keyboard to one of my projects and found firmware based on Atmel's AVR313 application note didn't work. After a bit of hunting around on the net and some careful watching on the logic analyser I found out why.

When the AT keyboard is first reset it's supposed to send an AA if its self-test passed or FD or FC if it failed. But before it does this, it sends a continual stream of AAs with the parity incorrect. Once the computer sends an FE to indicate that there is a parity error, the keyboard stops sending bad AAs and sends a correct AA or an FD or FC. This sounds like someone made a quick fix in the keyboard firmware for mis-matched reset timing (the keyboard always finishes resetting before the computer so the computer could miss the AA/FD/FC).

This was found at

Monday, August 06, 2007

Logger release 0.26

I've finally gotten around to doing a bugfix release for my Butterfly Logger. For some reason it would not compile properly on the later versions of gcc. I am still using gcc 4.02 for my development as it yields smaller builds than the current 4.1.x generation.

You can now remove some of the LCD/Joystick interface to make it smaller so the bootloader can be used on the butterfly.

The link to firmware download is on this page