[Dprglist] Encoder decoding

[David Anderson]

Howdy DPRG

As mentioned in the RBNV this evening,  Dave Ackley forwards the following logic table for decoding
quadrature encoder which are triggered on rising and falling edges of both A and B channels using XOR.


Channel A, rising edge.                XOR    Action
              Forward:  A = 1 and B = 1  0 => decrement \
              Reverse:  A = 1 and B = 0  1 => increment  \
                                                          \ Channel_A_Any_Change:
Channel A, falling edge.                                 /  If ( channel_A  ^ channel_B) count++;
              Forward:  A = 0 and B = 0  0 => decrement  /  else count--;
              Reverse:  A = 0 and B = 1  1 => increment /

------------------------------------------------------

Channel B, rising edge.
              Forward:  A = 0 and B = 1  1 => decrement \
              Reverse:  A = 1 and B = 1  0 => increment  \
                                                          \ Channel_B_Any_Change:
Channel B, falling edge.                                 / If ( channel_A  ^ channel_B) count--;
              Forward:  A = 1 and B = 0  1 => decrement  /  else count++;
              Reverse:  A = 0 and B = 0  0 => increment /

Thanks Dave.

cheers!
dpa

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