This Pmod features a rotary shaft encoder with an integral push button. It also includes a sliding switch that is commonly used as an on/off output.
A rotary encoder is most commonly used to detect how many "clicks" a knob has been rotated. This is the number in GTKterm labeled 'Encoder Value' and underneath that it records the angle.
We also created a knob for the top of the rotary shaft in order to increase stability and accuracy when rotating.
Initially we were hoping that we would be able to use the exact code and process that we use in Emily's previous blog 'Angle Encoder' but unfortunately we came across some problems. We were able to complete all of the steps successfully, however, we had some issues with the outputs. For example, when using the ALPHA encoder we were easily able to recognize a pattern within each click of the LEDs but with the new encoder we were unable to find any sort of pattern at all. The LEDs seemed to be lighting in a random fashion and the Encoder Value was not counting consecutively like it should be. Instead, it would repeat numbers several times and jump around.
We checked the Pmod connections to the ZedBoard, which were correct so we know that is not the problem and we also checked to make sure it was receiving power. We measured the output to be about 3.3 volts so that is also not where the issue lies. At this point we think that the problem is most likely somewhere within the code.
If we had some more time we would try these options provided to us by Mike:
1. Disconnect the encoder from the PMOD and hook it up to a breadboard. Then use wires to connect back to the PMOD appropriately. I have a feeling that the way the encoder is set up, it has the encoder pins opposite of the ones we are used to. So essentially, the output pins from the encoder would have to be switched (using wires) to connect to JA1 and JA2.
2. Leaving the encoder attached to the PMOD, change which input is the MSB. I mean that somewhere in the code, in the interrupt function, you are reading from both encoder pins, then combining the two read values into one. If it says MSB >> LSB, change it to LSB >> MSB. I do not remember the exact structure of the code off the top of my head, so you'll have to do some messing around.
3. If both above options fail, and you really want this thing to work before you leave tomorrow, get a multimeter out, hook up power to the power pin of the encoder, and see what each encoder pin is spitting out as you rotate the shaft. If it is a different readout then what you get from the other encoders, then you'll have to do some restructuring of the code to get the encoderValue to change when it is supposed to.
4. BEFORE YOU TRY ANY OF THESE THOUGH, make sure the design is working correctly with the other encoders. This will eliminate a lot of troubleshooting because the issue could lie with the PMOD rather than the enocders or the software.*-+
Helpful Links:
https://reference.digilentinc.com/_media/pmod:pmod:pmodENC_rm.pdf
To Be Continued...
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