I want to scan 88 keys on a piano with photosensitive sensors and was thinking of using either shift registers (74hc165 and hc595) or port expanders (mcp23s17).
Actually I need to scan a total of 3 x 88 = 264 sensors. Each key uses 3 sensors. 2 sensors to measure velocity and 1 sensor to determine whether a key is being kept pressed down.
I need a fast bus and thought about SPI. However I’ve read that the SPI distance limitation is about 10-20cm ?
Can it work, given that the 88 keys are spread over a distance of 1.5m.