Following on from an earlier question where the implementation was flawed, can anyone advise if the below is a viable implementation of a circuit to handle a matrix keypad?
The idea is that one keypad column and one GPIO pin (1, 2 or 3) will be 'active' at any one time. This will sequentially flick between the 3 column/pin combinations. The optocoupler will turn on when a keypad button is pressed which will 'activate' (i.e. trigger a change) in GPIO 4.
There would be an optocoupler for each row - I have only included 1 on the diagram to keep it condensed. "in" is the LED anode/cathode and "out" is the photo transistor collector and emitter.
It's a learning exercise on the 555 and 4017, more than anything so any other pointers would be much appreciated.