They may be turned simoultaneously also.
So what speed are we talking about here? And how many steps per revolution?
The options are:-
- Interrupts - you need to arrange things correctly so that one interrupt does not mask the other.
- Software polling, but depending on the speed required you might not be able to go fast enough.
- Small circuit to change the signal into step and direction.
- Conversion into a hardware count. Then each encoder has its own up down counter and you read that counter.
Are these encoders optical or contact. If they are contact then you have switch bounce to consider.
Is it really that important not to miss a pulse?