user2967: I bought a 12-step "quadrature" incremental rotary encoder as an input device for a project I'm working on. 
When I wrote the code to track "ticks" of rotation, I made it respond to any change in the "A" pin. As a result, I got 24 steps, not 12. They appear to be evenly spaced, and still correctly indicate clockwise or counter-clockwise rotation.
It occurs to me that if I track changes of state in both the "A" and "B" pins, as long as I reverse the logic for identifying clockwize vs. counterclockwise rotation, I could get a 48 step count from the same encoder.
Thus isn't it straightforward to get 2X or 4X the steps from a quadrature  rotary encoder simply by interpreting the signals differently?

user27653: Maybe the encoder you got is being incorrectly described?  I have a handful of the little thru-hole rotary encoders popular in Arduino module kits and they have 12 detents for one rotation, but they are actually 48-position-per-rotation encoders. When I use them, I have to divide the tick count by 4 to have one physical "click" count as one tick in my code.
For some of these, it's fairly straightforward to open them up and remove the detent, and thus get a higher-resolution, smooth spinning encoder. Unfortunately, others, such as the ones I have, are difficult to open without destroying them, and since they physically snap to the detents, aren't usable at the proper resolution.
The method you note, where you track the high/low change in either direction of both outputs is the normal way to read quadrature encoders.

2967: <p>I bought a 12-step "quadrature" incremental rotary encoder as an input device for a project I'm working on. </p>

<p>When I wrote the code to track "ticks" of rotation, I made it respond to any change in the "A" pin. As a result, I got 24 steps, not 12. They appear to be evenly spaced, and still correctly indicate clockwise or counter-clockwise rotation.</p>

<p>It occurs to me that if I track changes of state in both the "A" and "B" pins, as long as I reverse the logic for identifying clockwize vs. counterclockwise rotation, I could get a 48 step count from the same encoder.</p>

<p>Thus isn't it straightforward to get 2X or 4X the steps from a quadrature  rotary encoder simply by interpreting the signals differently?</p>
 27653: <p>Maybe the encoder you got is being incorrectly described?  I have a handful of the little thru-hole rotary encoders popular in Arduino module kits and they have 12 detents for one rotation, but they are actually 48-position-per-rotation encoders. When I use them, I have to divide the tick count by 4 to have one physical "click" count as one tick in my code.</p>

<p>For some of these, it's fairly straightforward to open them up and remove the detent, and thus get a higher-resolution, smooth spinning encoder. Unfortunately, others, such as the ones I have, are difficult to open without destroying them, and since they physically <em>snap</em> to the detents, aren't usable at the proper resolution.</p>

<p>The method you note, where you track the high/low change in either direction of both outputs is the normal way to read quadrature encoders.</p>
