Tx signal falls down as DMA data transmition starts

Hi,

 

my configuration includes AD-FMCOMMS4-EBZ and a custom carrier board based on Xilinx ZynqMP (xczu3eg). For that I took ADI HDL design (2018_r1 git branch)for fmcomms2/zcu102(xczu9eg) and adopted it for my board. I also built Linux with external kernel sources (I took also ADI 2018_r1 kernel) and libiio.

Below you can see the signal picture I took with iio-osscilloscope

But if I start data generation with libiio/libiio-examples/ad9361-iiostream the signal disappears.

I thought, that DMA data transmission does not work, but if I enable digital loopback (echo 1 > /sys/kernel/debug/iio/iio:device1/loopback) I receive expected data in ad9361-iiostream (I added sending of non-zero data and check of received data), which means DMA data transmission/reception works.

 

What can be wrong/missing in my case ? Please let me know which additional details you need to analize the problem.

 

I need help as soon as possible (this the second time I create this question - the first request silently disappeared).

 

Best regards,

Timur.