I got my PS2 adapter in the mail today. Rob, this thing is really impressive!

I tested an old Compaq PS2 keyboard with a Mac Plus. I don't have a DB-9 cable yet for mouse testing, and I don't have an ADB Mac handy either. I can confirm that it works with the Compaq keyboard. It's quite a trip, typing on a Mac Plus with a PC-style 101 key keyboard! A few bug reports:

• The adapter doesn't seem to work when first powered on, until you press the reset button. I'm not sure if that's expected. After pressing the reset button, a blue LED labeled LD4 turns on, and the adapter works. But at first power-up, LD4 is off.
   
  A few keys on the numeric keypad do unexpected things: The numbers, decimal point, enter key, and the - minus sign work. Num lock does nothing, which is fine. / (forward slash) functions as up arrow. * functions as right arrow, + functions as left arrow.
   
  I also got into a state where the arrow keys did nothing. But after a reset, they worked again. Another time I got into a state where left arrow would type +, right arrow would type *, up arrow would type slash, and down arrow would type =. I think maybe I got this to happen by holding down the arrow keys until the key repeat action kicked in, but not sure.
   
  Function keys, print screen, scroll lock, and pause/break do nothing, which is what I would expect.
   
  I got into a state where Caps Lock turned on the keyboard's indicator LED, and letters typed appeared in all caps. Pressing caps lock a second time turned off the LED, but the keyboard remained in all caps mode. There didn't seem to be any way back to normal mode, expect to reset the board. I tried that test a second time, but couldn't repeat it.

Also a couple of thoughts about the board itself, if you ever decide to do another revision:

• It's 4-ways ambiguous which way the adapter board should be connected to the ST discovery board. It could conceivably be plugged in with the ARM chip facing the adapter board, or away from it, and with the USB port on the same end as the PS2 ports, or the opposite end. In fact I pulled the two boards apart as an experiment, then forgot which way they go together again. Can you remind me? I remember that the ARM chip was away from the adapter board, but not which ends were aligned. An outline of the ST board in the silkscreen on the back of the adapter board would help.
   
  The alignment of the two boards seems backwards to me. You end up with a two-board sandwich with nothing on the inside, and components on the outside. Since you can rest the sandwich adapter-side down (the DB-9 mouse cable would interfere), you have to rest it on the desk with the ARM components on the desk, so the weight of the whole thing is supported by the reset button. Luckily it's a fairly stiff button, but I think it would be nicer if both boards had their components on the "top".
   
  Lastly, I think you could make the adapter board much smaller, and save some money on the PCB. I there a reason the adapter board needs to be the same size as the discovery board? It looks like you could make a smaller board that just connects to the 10-or-so pins on both sides of the USB-end of the discovery board, as that includes power, ground, and a bunch of digital I/Os. Then your board could be about 1/3 the size it is now.
   
  As discussed earlier, it would also be nice to have support for regular phone cable as well as keyboard (reverse-polarity) cable.
  

Once again, great work! I'll report in again once I have a DB-9 cable, and drag an ADB Mac out of storage for testing. Meanwhile if you can tell me how to plug the two boards back together, I'd appreciate it. :I