Update: Images from this post have been lost
The components have arrived! At least some of them. We have all the correct resistors and enough buttons to make 2 guitars. Unfortunately there was a mix up with the matrix boards and they weren't added to our order. We continued work and made a second order consisting of matrix boards, button caps and arudino micros which we decided will be more convenient as they can work as USB hosts. We decided it was time to record some voltages! We recreated last weeks circuit design (with our new components) on a breadboard and recorded the voltages when each button was pressed. We then calculated the voltages when 2 buttons were pressed at once. We noticed very minimal overlap and more or less every combination had a unique voltage. These values were not final though. When we connect up 4 rows of buttons (corresponding to 4 strings) all leeching power from the same 5V output, the voltages will be lower. Unfortunately we could not test this until the larger matrix boards arrive. Either way, it was time to write some code! We started protoyping the initial architecture for the arduino sketch. Everything seems in order and as soon as we receive our matrix boards we can start crafting a prototype of our invention.
--Marcin Dyszynski