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NEED: Complete Instructions To Use XADC Header

Former Member

So we have 3 differential channels to use with this XADC header:

VP/VN,
VAUX0P/VAUX0N
VAUX8P/VAUX8N

I'm sampling at 1 KHz so timing is not an issue for me with the internal mux setup of the XADC.

I see that the requirement for the XADC inputs is a 1V peak-to-peak differential. What is the common-mode voltage? Is it vref (1.25 V)?

What ports do I have to provide other than the differential data lines? Which of the following are already provided for by the board (ie. which are driven out from the XADC header?):

Vref
VCCADC
AGND

How many of our Zedboard brethren have started to do designs that require external sensors and ADCs anyhow? What are your experiences with the XADC header? I didn't find the HW manual itself to be too helpful, and the only "tutorial" uses the onboard thermal sensor. Obviously this is insufficient for applications relying on external sensors.

Thanks

  • 0

    I purchased the AMS101 and got it to work on the Zedboard.

    The limitation of the AMS101 is that the source design for interface is not provided. The design only includes a boot.bin file that you load through the SD card. It then interfaces with a proprietary panel on the PC.

    As such, the AMS101 kit provides no examples on how to configure the Zynq in hardware and no examples for software interface either. It just has a demo of the final working system.

    In general, each input ADC pins can only handle positive voltages between 0 to 1V (full scale) on each pin. In some differential modes, you can also have 0.5V common, so one pin can go up to 1.5V. See details below. Bipolar can do +/-0.5V, but that's relative with a 0.5V common. Again, each input must be positive between 0 and 1V.

    The Zedboard creates the XADC-VCC5V0 on pin 13 by filtering the VCC5V0 signal through a ferrite bead. Zedboard creates the analog ground (pins 4,5, and 10) by a ferrite bead from digital GND (pin 16), and the AMS01 also has a ferrite bead between these grounds.

    Useful information can be found in the following documents that can be found on the Xilinx site.

    For specifications:
    ds187-XC7Z010-XC7Z020-Data-Sheet.pdf
    ds191-XC7Z030-XC7Z045-data-sheet.pdf

    For Theory and Concepts:
    ug480_7Series_XADC.pdf

    How it fits with Zynq:
    ug585-Zynq-7000-TRM.pdf

  • 0

    Is there a way to just input a voltage and read it through the terminal using the XADC Header on the Zynq 7000 Zedboard? If so can this be done using the VP VN pins?

  • 0

    Hello Se31berg,

    For educational support please ask  your question over at Digilent. Thank you.

    --Josh