Hi there,
I am using the keys from my old piano (Yamaha PSR-75) as the internal circuitry does not work anymore and i would like to recreate the piano. The problem that i am having with doing this is the way that the keys are wired. There are 49 keys on the board but only 15 pins coming out. I have traced how each key is handled and it uses a combination of the pins to complete a circuit. The last 6 pins from the ribbon are a positive input (diodes on the board ensure this) and go through to the first 9 pins to make a set of 9 lots of 6 (54) so that all of the keys can be measured. This is where the problem lies: i can easily get a single or one set of inputs through the board but it has to go to the ground pin on the arduino. I cannot find a way to read a negative current from the arduino input pins to tell the combination of which positive and negative pins on the keyboard are closed.
I have uploaded pictures of the input board below (sorry for size), i have also given an example of the key mappings below
Thanks heaps in advance
(Shows the combination of positive and negative power and what key it maps to)
Positive into pin 10:
1st pin is 8th key
2nd pin is 38th key
3rd pin is 2nd key
4th pin is 32th key
5th pin is (no key used)
6th pin is 26th key
7th pin is 44th key
8th pin is 20th key
9th pin is 14th key
Positive into pin 11:
1st pin is 9th key
2nd pin is 39th key
3rd pin is 3rd key
4th pin is 33th key
5th pin is (no key used)
6th pin is 27th key
7th pin is 45th key
8th pin is 21th key
9th pin is 15th key
