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Newbie sidali240
Newbie
8,018 Views
Registered: ‎04-30-2015

XADC external input on PetaLinux

Hi everyone,

 

I would like to use petalinux on Zedboard to get "analog input" via the XADC interface, unfortunetly after building making the project in Vivado then building the petalinux with XADC drivers I can only see internal temp sensor ...

there are no external Voltage acces in command line.

 

sas.png

 

I'm stuck and it's been 15 days without giving anything.

Thank you in advance

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2 Replies
Visitor akohlsmith2
Visitor
7,650 Views
Registered: ‎10-14-2015

Re: XADC external input on PetaLinux

This is really late coming for you but I'm posting for posterity.

 

The XADC manual states that if the XADC is *not* instantiated in the PL then a "default" one is instantiated which sequences through all the internal sensor channels and sets up a default calibration and averaging. You won't have access to external voltages, although the driver will act as if you do.

 

If you want to measure the dedicated Vp/Vm or any of the 16 external inputs you need to instantiate and XADC core in the PL. If you don't need high speed access you do not have to use the AXI interface, and if your PL does not need to drive the XADC, you do not need to instantiate the DRP. e.g. if all you want to do is periodically read the channels you can select the "None" interface, which is a little counter-intuitive.

 

You don't need an external clock, you don't need an external reset. Enable the external analog channels you want to use (their pins will now show up), configure scanning and averaging if you don't want to set it up in the driver, and then go and wire up the external analog pins how you want.

 

In Vivado you'll need to set up the pins (everything is in Bank 0 so I think 3.3V is the default voltage level, etc.). Once you have your new bit file you can load it and now your external channels will actually report something useful.

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Scholar vanmierlo
Scholar
7,635 Views
Registered: ‎06-10-2008

Re: XADC external input on PetaLinux

I experimented with the XADC on a Trenz Zynq module and was greatly disapointed with the performance. Even with both inputs (P & N) connected to GND I still had 5 bits of noise leaving about 7 significant bits. And that was after averaging!

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