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Input to XADC with BKO Card

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trillian
Junior(0)
Input to XADC with BKO Card

Hi there,
I have a MicroZed 7020 Board and want to read VN/VP values. Vor my IO Ports Vivado lets me only choose Package Pin L10 and K9.
Ok, so I look into the HW Guide (http://microzed.org/sites/default/files/documentations/MicroZed_HW_UG_v1...) and on page 17 it tells me I reach those pins through JX1 97 and 99..
So I switch to the BKO Schematics (http://zedboard.org/sites/default/files/documentations/MBCC-BKO_RevA_Sch...) to find out what pins its going to be on my breakout board. I would assume I connect my input signal to whatever pins are connected to JX1 97 and 99.
but that document says JX 97 and 99 are tied to ground? Besides I cant reach 99 from the BKO Board.
What am I missing here?
What pins on the breakout board do I have to put my input signal on?
thanks!

trillian
Junior(0)
(couldnt ask everything because the forum coniders it as spam ..

Also I am a puzzled by the red naming convention in the BKO Schamtic like IO_L11N_T1_34 and IO_L11P_T1_34. They seem to be P/N pairs.. how does that work? why is that? lets say I have an LED I want to blink. So I only need one pin and ground. lets say IO_L11P_T1_34 and Ground. what would happen to IO_L11N_T1_34? Are they related other than in the naming?

JFoster
Moderator(76)
Hello trillian,

Hello trillian,

Yes i see on the BKO those pins are routed to GND. If you want to use those pins, may i suggest using The MicroZed IO Carrier Card?

You can split up a differential pair into two seperate pins. It will not have any adverse affect.

-Josh

trillian
Junior(0)
Hi Josh,

Hi Josh,
thanks for your response. I'd prefere the BKO for its smaler size.
About the Package Pin L10 and K9 ..those are the dedicated VP/VN pins of the XADC. I was under the impression that those are prefereable for Voltage meassurements over the other IO pins. Is that not right or is it assumed I wouldnt want to work much with the XADC if I use the BKO? I was about to solder some SMB connectors on it! :D
thx!

JFoster
Moderator(76)
Hi Trillian,

Hi Trillian,

Looking at the HW User GUide for the BKO, it states "– Bank 35 exposes several I/Os that may be used as analog inputs to the XADC, but the end user is responsible for adding the applicable filtering in the prototype area."

Try taking a look at the pins on bank 35.

-Josh

trillian
Junior(0)
Hi Josh,

Hi Josh,
you are right, the BKO HW User Guide states that one can use Bank 35 IO pins. In order to use these, you have to configure the XADC to use Xaux pins. I tried that and it works (not in my design yet but I can see my signal on the xadc monitor)
however, I was talking about the "Dedicated Package Pins" from Bank 0 as described on Page 15 from the XADC Reference Manual https://www.xilinx.com/support/documentation/user_guides/ug480_7Series_X...
So for anybody who finds this with the same question I know now for certain: It does make a difference if I choose the dedicated or auxiliary analog channels. UG480 Page 30 for example states: For the dedicated channel (VP/VN), the minimum acquisition time (bipolar mode) required is 3 ns while it is 300 ns for any auxiliary channel.
But anyways, it is clear to me now that I have to use Vaux as long as I'm working with the BKO Board. Thanks!