Looking at a common module for a rotary-encoder, there are 3 pins called "SW, DT, CLK". I learned that they are for the button when you push down on the rotary-encoder, output B, and output A, respectively. Why are they like that and not "SW, B, A". Sounds like a communication protocol pinout.
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2 Answers
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But in the pictures CLK is the encoder A pin and DT is the encoder B pin.
And if you consider one of the pins as clock pulse, the state of data pin on the active clock edge will tell you which way the encoder was turned.
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Figure 1. The underside of the PCB reveals a little. (Image source from Amazon ad linked in OP.)
simulate this circuit – Schematic created using CircuitLab
Figure 2. Best guess at circuit.
- The three outputs are normally pulled high by 10 kΩ resistors.
- A & B will give quadrature encoded output signals which allow a controller to sense direction of rotation and angle turned.
- SW will be normally high and pull low when pressed.
Detecting direction of rotation:
- If we write the firmware to trigger on every 0 → 1 transition of the CLC pin we can then check the DT (direction of travel?) pin to sense direction.
- As shown (possibly incorrectly) in my diagram, if DT is low on the CLK 0 → 1 transition then we are going clockwise so count UP.
- If DT is high on the CLK 0 → 1 transition then we are going anti-clockwise so count DOWN.
Amazon is not a good site with respect to datasheets and my analysis makes some assumptions so you should check with a continuity tester. You can see that a simple diagram would solve any confusion.
