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 #5.5 Rotary Encoder
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Rotary encoders also know as Quadrature Encoders
   
 

 

Note!!!!  How the PmodENC should be connected (watch the flower - and the "missing" flower)
 

 

Ideal and "real-life" encoder signals

 

Example of an Asynchronous filter for the Encoder (S-R latch based)
In real-life encoders, specially the ones based at mechanic switches, will bouncing appears each time a switch open and closes.  (*)

By using the fact that one signal always stable while the other changes states can a simple filter be constructed.

However must we accept some form of delay at least in one direction of turns.

There's also a chance / risk that pulses could be last. which could course problems in some applications.

(*) Due to the laws of Murphy will this not happen if you actually wants' it :-)

 
 
 

Example of an Synchronous filter for the Encoder (D F/F based)
Basically the same logic as for the Asynchronous but now with a clock signal and hence will this force the synthesize tool to use Flip/Flops.

The Clk signal must have a higher frequency then the A and B signals changes.

 
 
 

Example of circuit which detects changes and direction.
 
 
 
   

 
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