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Post: The internal resistors on the IO Pi Plus are pull-up rather than pull down so to use them you would need to connect the button to ground instead of 5V so when you press a button it shorts the input to ground. The side effect of this method would be that the inputs would be inverted so when the button is pressed the input goes to 0 instead of 1. This means that you would need to invert the values from bus 1 before writing them to bus 2 otherwise the LEDs would be on all of the time and go out when you press a button. You can stack up to 4 IO Pi Plus boards on a Raspberry Pi so you could have up to 64 buttons and LEDs connected. You just need to change the solder bridges on the address select pads to give each board a different pair of addresses. One thing to note is the maximum current the IO controller chip can source is 125mA so if you have 16 LEDs connected and being lit at the same time you would only be able to safely drive 7.8mA to each LED. If you use lower current LEDs and 680R resistors this would keep the total current below the 125mA maximum. Alternatively, you could use external transistors or Darlington arrays to drive higher-current LEDs.