I can get these locally for $6.
Great price for AVRs.
Can i make my own button layout?
Once the KADE loader program releases, it will be pull-down menu easy to do custom layouts.
If you use the older AVR Encoder firmware, you have to edit the source code to reprogram it or get Degenatrons to whip you up a custom map like in
this earlier post.
I have 22 buttons but it says only 21 connectors? I have 2 joysticks, 6 main buttons, 1 and 2 player buttons and 6 option buttons.
AVR has 24 pins - 20 normal/programmable inputs + ground + 5v output + Reset + HWB. (Hardware Button = mode/group change in AVR and shift function in KADE IIRC)
Given that you want 8 (2 start + 6 other) admin buttons, it looks like the AVR Encoder firmware won't work for this application, unless you use 2 encoders.
The KADE firmware can do this easily with up to 20 shifted inputs.
*** Haven't tested this yet, but you'll probably need 1 diode per shifted function line to prevent activating all shifted functions at once, similar to this method for wiring Magnasave and upper flippers in parallel with MAME keys.

Without the diodes, pressing any of these 3 buttons will output "A" and "L-Ctrl."
Also, any difference between the regular one and the 32k one? The latter is only $2 more.
KADE loader will work with either board and several others IIRC.
No real advantage for this application that I know of to the 32K one, since the regular one can hold at least 23 maps, based on the latest AVR Encoder firmware.
Scott
***EDIT: Just remembered that the diodes are only needed to do a 1-button push shifted function. A 2-button push shifted function will not require diodes.
Take a look at
this setup. It allows either a 2-button press (left side only) or 1-button press. (4 upper switches)
Thanks to RandyT for the easy-to-follow diagram.