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214 Views
Registered: ‎10-21-2019

Output unstable in FPGA or whatsoever. Logics are correct

I'm doing a audio signal project with pynq-z2, where I use an 3.5mm headphone jack to hear my output. But it only outputs noises, which sound like step functions every few seconds. The same happens to my LED when I do a simple PWM output. The LED is supposed to maintain a stable brightness but it turns max brightness and instantly back to normal (or sometimes off and on) every few seconds... Even  the orange LED of the Ethernet port... Also these things happen at the same time. I believe it's not my design error. What's the problem? I'd appreciate it if some experts could help me with this!

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4 Replies
Scholar drjohnsmith
Scholar
205 Views
Registered: ‎07-09-2009

Re: Output unstable in FPGA or whatsoever. Logics are correct

You are brave to state its not designer error ,

you need to divide the problem

has this system worked before ?
is it a standard board or a custom ?
change the cables, board and power supply,

my guess is its a power problem, some sort of broken lead, or your shorting
when you move things around, plug in cable or something,

<== If this was helpful, please feel free to give Kudos, and close if it answers your question ==>
178 Views
Registered: ‎10-21-2019

Re: Output unstable in FPGA or whatsoever. Logics are correct

1. This system has not worked properly before. I've tried others' board(same model) and they have the same issue.

2. This board is from TUL.

3. The issue seems to happen without external interference.

And the issue happens like every 2.5 secs.

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Scholar drjohnsmith
Scholar
163 Views
Registered: ‎07-09-2009

Re: Output unstable in FPGA or whatsoever. Logics are correct

Have you tried different power supplies and cables,

If you have , Id get back to TUL if I was you
<== If this was helpful, please feel free to give Kudos, and close if it answers your question ==>
156 Views
Registered: ‎07-23-2019

Re: Output unstable in FPGA or whatsoever. Logics are correct

 

so you have:

"an audio signal project" - do you agree this says nothing?

"a noisy output" - do you agree that "noise" is subjective? What did you expect? Better than hearing, can you use an scope?

"the same happens to your LED" - If you send a PWM to an LED and brightness changes, that means you are, on purpose or not, changing the duty cycle (or the frequency with the same duty cycle)

If the ethernet LED does the same thing, synchronously with your sound and other LEDS, I'd suspect:

- some electrical fault (hopefully not)

- a problem with interrupts or watchdog that freezes normal execution

- some regular reset (that might be for an electrical fault as well). and by "electrical fault" I'm thinking of anything that causes the board malfunction, so actually a bit of a recursive definition

 

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