Happy to report that I have got gqrx running on an XU3 using a LimeSDR as the radio, and displaying to the HDMI port at 1920*1080. So far no recurrency of the black screen bug - I suspect the Mali driver has been updated
I used the ubuntu 16.04 image on an eMMC card, and added the recommended PPAs for limesdr and soapy. It nearly worked without manual hacking…
Things I had to hack by hand
gr-osmosdr for ARM is not compiled for soapy, so you must download libsoapysdr-dev, then build gr-osmosdr, then copy the new libgnuradio-osmosdr.so.0.1.4 to /usr/lib/arm-linux-gnueabihf. Do NOT uninstall gr-osmosdr, since make install does not install osmocom_fft etc.
To get the headphone socket to work -
as supplied it’s an XU4 image, so edit /media/boot/boot.ini and add
setenv board_name "xu3"
just before it selects the .dtb to be loaded
you’ll need to select headphones in pavucontrol. NOTE: gqrx hangs with no graphical window if pulseaudio isn’t running
With graphics running and LimeSDR over USB3, my limit is 3.5 Mbits sample rate - beyond this the audio gets choppy. You still need to select Other : device string soapy=0,driver=lime to select the LimeSDR
At last the XU3 is usable, now I can explore the LimeSDR further.