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Contributor
Contributor
1,166 Views
Registered: ‎01-02-2015

RFSoC DAC to ADC loopback

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I'd like to build in a DAC-to-ADC loopback on the RFSoC for testing. It doesn't appear that the RF Data Converter already has any support for a loopback mode.

Is there any reason why I shouldn't simply loop the output of a DAC back into an ADC in user logic? 

Thanks,
Will

 

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Moderator
Moderator
1,158 Views
Registered: ‎04-18-2011

Re: RFSoC DAC to ADC loopback

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Hi @wdecook

So you want to build a design where you take data and transmit it out from the DAC then loop this back to the ADC analog input?

Of course this is allowed. 

Just so we are clear there is no internal connection on the die to connect a DAC output to the ADC like you get with the near end loop back mode in the GT. 

One thing you should also look at is RF Analyzer. It is a tool that can be used to control the ADC and DAC tiles. It uses a gui for analysis and you can dump out and load data in the lvm or tdms standard formats from Labview. We also give you some utilities to generate TDMS from Matlab  Mat files. 

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Moderator
Moderator
1,159 Views
Registered: ‎04-18-2011

Re: RFSoC DAC to ADC loopback

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Hi @wdecook

So you want to build a design where you take data and transmit it out from the DAC then loop this back to the ADC analog input?

Of course this is allowed. 

Just so we are clear there is no internal connection on the die to connect a DAC output to the ADC like you get with the near end loop back mode in the GT. 

One thing you should also look at is RF Analyzer. It is a tool that can be used to control the ADC and DAC tiles. It uses a gui for analysis and you can dump out and load data in the lvm or tdms standard formats from Labview. We also give you some utilities to generate TDMS from Matlab  Mat files. 

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Contributor
Contributor
1,145 Views
Registered: ‎01-02-2015

Re: RFSoC DAC to ADC loopback

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Hi @klumsde

So you're saying that this can't be done internally to the device? Instead, I'll need to route a connection on my pcb between the DAC and ADC. Furthermore, if I want to be able to switch the input of the ADC between the DAC output and some other external RF signal, I'll need an RF mux or some off-board connectors that can be tied together as needed. 

Does this sound correct?

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Moderator
Moderator
1,127 Views
Registered: ‎04-18-2011

Re: RFSoC DAC to ADC loopback

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You are correct, there is no path on the die from the DAC output to the ADC input. 

In my case I have the zcu111 evaluation board and I loop the DAC signal back via xm500 card so the loop back is done totally external to the board. This obviously avoids muxing the signal etc

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Participant pavithrasyadav
Participant
638 Views
Registered: ‎04-29-2019

Re: RFSoC DAC to ADC loopback

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after connecting the ADC_T1_CH1 to the DAC_T1_CH1 on XM800 through SMA cables what are the steps to be followed on RFDC GUI to get the DAC output routed to ADC input so that I want to see input of DAC on ADC FFT page. Currently I can able see the DAC output. But no response on ADC. I have loaded the loopback configuration file RFDC_example_BRAM_ADC_DAC_8x8_Loop_C2R_x8_3932P16.cfg. Should I have to load the preferences files also. If so please let me know the sequence of loading config and preference files. 

thanks in advance 

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Participant pavithrasyadav
Participant
621 Views
Registered: ‎04-29-2019

Re: RFSoC DAC to ADC loopback

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XM500
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Participant nicolas05
Participant
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Registered: ‎06-05-2019

Re: RFSoC DAC to ADC loopback

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In my case I have the zcu111 evaluation board and I loop the DAC signal back via xm500 card so the loop back is done totally external to the board. This obviously avoids muxing the signal etc


Hi @klumsde ,

In my case the loopback is made from ADC to DAC and I need to connect a wave generator (as input) and an oscilloscope (for measuring DAC's output). In the case of the ADC conection, I need to plug the wave generator input but also connect the ADC to the DAC tile. Would a RF splitter work in that case?

Thanks!

 

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Moderator
Moderator
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Registered: ‎04-18-2011

Re: RFSoC DAC to ADC loopback

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I'm not sure I follow you... 

ADC to DAC loopback is done inside the programmable logic. The ADC output is coming out of the tile via an axi streaming interface in the pl fabric, then you can connect it in the programmable logic to the DAC streaming interface... 

 

 

 

 

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Participant nicolas05
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Registered: ‎06-05-2019

Re: RFSoC DAC to ADC loopback

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Hi @klumsde,

 

You follow me perfectly, thanks! I have drawn my setup for a better explanation.

In the RF data converter IP I have indeed connected the ADC output to the DAC input. As I understand from this thread, I also have to make the physical connection in the XM500 board, meaning that I can not connect any other device to the ADC or DAC connectors in the board (e.g. generator to ADC), unless I use a RF splitter..., I believe Thanks!

rf splitter.jpg

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Moderator
Moderator
245 Views
Registered: ‎04-18-2011

Re: RFSoC DAC to ADC loopback

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I am still not sure what it is you are trying to do here. 

To me there are only really 2 valid ways to make a loopback 

First is this way:

DAC drives out a signal from the fabric that gets looped back around to the ADC input. There is the option of using a splitter to take this signal to a spectrum analyzer as well. zcu111_analog_loopback.JPG

Second is that you drive the ADC input (option to use a splitter to take the signal back to a scope), loopback to the DAC in the PL Fabric over AXI Stream and observe the DAC output with the scope. 

zcu111_digital_loopback.JPG

 

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Participant nicolas05
Participant
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Registered: ‎06-05-2019

Re: RFSoC DAC to ADC loopback

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My case is the second one. Now I understand, there is no connection between the SMA ports in the XM500, thus no need for any RF splitter, apart from the one used for the Scope. Thank you again!
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