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Registered: ‎01-31-2018

XADC doesnt measure the correct value when default values for axi-gpio are set


I came across some strange behaviour and hope someone can give me a hint.

Besides other things we use the xadc-core and the axi-gpio-core in our design. Both work well on there own.

When I set the default values for the axi-gpio-core via the "Block Design"-UI and did run some tests I noticed that one value from the xadc was much lower then expected. After some further testing (remove default values, etc.) it was clear that setting the default values for the axi-gpio-core would somehow influence the xadc-measurements. To be exact it always influenced the measurement of two signals which are connected to vauxp13/vauxn13 which are connected to the fpga-pins G19 and G20. When the default values where set the xadc measured something between 50mV and 0mV, without the default values it measures something like 500mV. Nothing else was changed in the whole setup so Im sure the cause for that are the default values for the axi-gpio-core. There is also no relation between the xadc- and gpio-core in the design. The gpio-core handles some gpio's which have nothing to do with the measurements.

Like I mentioned the affected pins/ports of the xadc are:

  • G19/vauxp13
  • G20/vauxn13

The gpio-core is connected to the following pins:

  • H20
  • J20
  • N17
  • P15
  • P16
  • P18
  • P20
  • R16
  • R17
  • U18


Does someone know what is happening here ? Can you give me a hint what the problem could be ?

I further information is needed please let me know.

Thanks in advance.


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Registered: ‎04-18-2011

Can you tell us the device and package you are using?

Is this your own board or is it a Xilinx Development Board?

I am not too sure how the GPIO can interfere with the VAUX measurement but it would make sense to give us the device and package as well as snippet of the schematic showing how this is all connected on the board. 




Don’t forget to reply, kudo, and accept as solution.
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