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Running separate modules simultaneously on Basys 3 Board.


Jayanth

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Hello, I am trying to run a speed detection module using the Basys 3 board and based on the error between the measured speed and desired speed generate a PWM wave. I can do either of these tasks individually. But when I try to run them together, they start malfunctioning. The seven segment display showing the speed begins to show random values and the PWM wave becomes a very noisy wave. Further, toggling the switches to set the desired speed input also leads to a noisy output. There's no problem with the simulation using Vivado Design Suite. What should I do to run these modules together?

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I am measuring the speed of a DC motor using a hall effect sensor. I am counting the number of times the hall effect sensor output goes from low-high in a second and determining the rpm and displaying this value on the seven segment display. The output of the sensor is connected to the Pmod pins. I am also generating a PWM wave and output it through different pmod pins.

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@Jayanth,

Okay, that's a good start but ... honestly, at this point, with the information you've given, there are still just way too many possibilities of things that could cause it.

Let me just ask some basics then: are you using asynchronous resets?  More than one clock?  Transitioning on both positive and negatives edges of any clock?  Are you double clocking any asynchronous inputs before using them to avoid any metastability issues?

If you are using only one clock, and only the positive (or negative) edge of that clock (but not both), and you are properly registering every asynchronous input twice in order to transition clock domains then ...

The next possibility would be to look at how the two modules are interacting with each other.  Is there anything you can share there?

Dan

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I am using only one clock. And I am using only the positive edge of the clock. And the Reset is synchronous. The 2 modules don't have much in common. The only interaction is that the measured speed is used to get the error value. And using this error value, the duty cycle of the PWM wave is obtained. No other interaction. 

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