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Contributor
Contributor
1,435 Views
Registered: ‎02-19-2017

Vivado ILA shows less samples for a sine wave

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I am interfacing TI ADC with VC707 kit and use ILA to show the results from ADC. The input clock of ADC is 182MHz(sampling rate), and input signal is of 1MHz (sine wave). Below is the RTL diagram of code.RTL diagram.JPG

The ILA should show a sine wave of 1MHz having 182 mega samples in one cycle of 1MHz, but it only show a sine wave with just 182 samples.

sampling182MHz,signal 1MHz.JPG

 

Can any body tell me what i am doing wrong.

 

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RTL diagram.JPG
sampling182MHz,signal 1MHz.JPG
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1 Solution

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Adventurer
Adventurer
1,535 Views
Registered: ‎11-13-2017

Re: Vivado ILA shows less samples for a sine wave

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Hi,

Right now the ILA is sampling 182 Msps. The clock of the ILA is 182 MHz and it is recording 1 sample of the sine-wave every clock cycle leading to 182 Mega-samples-per-second.
The frequency of the sine wave has nothing to do with how often you sample it.
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7 Replies
Xilinx Employee
Xilinx Employee
1,427 Views
Registered: ‎08-01-2008

Re: Vivado ILA shows less samples for a sine wave

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you need to check your system clock on which you are reading samples. You may vary the clock and see number of sine wave cycles
Thanks and Regards
Balkrishan
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Contributor
Contributor
1,423 Views
Registered: ‎02-19-2017

Re: Vivado ILA shows less samples for a sine wave

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yes I have done that but get same results, the ILA has the same clock i.e 182MHz.

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Adventurer
Adventurer
1,410 Views
Registered: ‎11-13-2017

Re: Vivado ILA shows less samples for a sine wave

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The ILA should show a sine wave of 1MHz having 182 mega samples in one cycle of 1MHz, but it only show a sine wave with just 182 samples.

 

Sine wave period time: 1000 ns

Time between each sample: 5.49 ns

 

Number of samples in one sine wave period: 1000 ns / 5.49 ns = ~182 

Your results appear to agree with theory.

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Contributor
Contributor
1,374 Views
Registered: ‎02-19-2017

Re: Vivado ILA shows less samples for a sine wave

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@logictable thanks for your valuable answer, can you elaborate it more. the ILA do this by itself? as i need 182 mega samples for FFT core.

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Adventurer
Adventurer
1,536 Views
Registered: ‎11-13-2017

Re: Vivado ILA shows less samples for a sine wave

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Hi,

Right now the ILA is sampling 182 Msps. The clock of the ILA is 182 MHz and it is recording 1 sample of the sine-wave every clock cycle leading to 182 Mega-samples-per-second.
The frequency of the sine wave has nothing to do with how often you sample it.
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Contributor
Contributor
1,345 Views
Registered: ‎02-19-2017

Re: Vivado ILA shows less samples for a sine wave

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@logictable but when I increase the input frequency to 40MHz, the output result get distorted and not a pure sine wave now.sampling182MHz,signal 40MHz.JPG

sampling182MHz,signal 40MHz.JPG
sampling182MHz,signal 40MHz .JPG
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Scholar jmcclusk
Scholar
1,324 Views
Registered: ‎02-24-2014

Re: Vivado ILA shows less samples for a sine wave

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This is quite normal when the sine frequency and the sample rate are not related.   It's a just a visual artifact of the low number of samples per sinewave cycle.

Don't forget to close a thread when possible by accepting a post as a solution.
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