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Pmod ENC pinout question


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I have a Pmod Encoder. When I press the BTN (pin 3), VCC and GND are connected together through pin 3 (Not good). When I release BTN pin 3 is only connected to GND ( as I would expect). This makes me think that the Pmod is broken.

The encoder works as expected as well as SWT (pin 4). In one position it is connect to VCC and in the other GND.

I bought it a few years ago but only tried to use it recently. Can I get a replacement?

Thank you,


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Hi @almcgrath,

The behavior you are describing is the intended behavior for the button as per the schematic, https://digilent.com/reference/_media/reference/pmod/pmodenc/pmodenc_sch.pdf, and for wiring up buttons in general, with a pull-down (or pull-up) resistor holding the input to the host system at one of those logic levels and once the button is pressed, Vcc and GND become connected through the pull-up/down resistor, with the actual input receiving the other voltage. To be clear, the two voltages are not connected through the input pin 3 itself.

The series resistor on the pin 3 input, R6, is there to prevent a short from occurring if pin 3 was instead mistakenly set to be an output at GND logic level while the button was pressed.

Let me know if you have any questions.


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