Is your screen (via miniDP) working ?

. I am running the latest minimal image, just upgraded with the official procedure
. I have tested two screens and none of them is working, namely:
… Elecrow 5’’ 800x400 (this was tested working with BBB)
… Magedok 7’’ 1280x720 (tested working with other Linux boxes)
. I am using a miniDP <—> HDMI adapter branded BENFEI
. The screens power is taken from BBAI64 USB
. Both screen are not working, the only thing i see in the serial console is

[  897.878222] cdns-mhdp8546 a000000.dp-bridge: get block[0] edid failed: -22
[  897.885096] cdns-mhdp8546 a000000.dp-bridge: Failed to read EDID
[  898.636909] cdns-mhdp8546 a000000.dp-bridge: Failed to read receiver capabilities
[  905.058303] cdns-mhdp8546 a000000.dp-bridge: get block[0] edid failed: -22

Any ideas ?

@nmingotti My guess here is you’re running sans EDID info on either of the two monitors, so the BBAI-64 is outputting whatever default mode & clocks were deemed appropriate as default, which may or may not jive with your monitors.

BTW, I have my BBAI-64 outputting over a miniDP-DP cable to a Dell 24" 1920x1200 monitor. The output generally works, but it’s somewhat unstable – it appears to be losing sync sometimes, particularly during 60Hz kms fb swap sequences – the image is lost, only to return after a second or two. I do need to investigate this properly. It very much might be a similar ‘no EDID, just output at default mode & clocks and hope it works’ problem; if sufficiently close to what the monitor expects this might result in such intermittent losses of signal.

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Hi blu,
I have older notes for the BBBlack where i wrote this about making the screen work:

----- /boot/uEnv.conf ------------------------------
cmdline=coherent_pool=1M net.ifnames=0 lpj=1990656 \
  rng_core.default_quality=100 quiet video=HDMI-A-1:800x480@60e

Maybe a directive like that may work also for BBAI64 but since /boot/uEnv.conf
is gone i don’t know where to try inform the system about the screen resolution+freq now.


@nmingotti I think you can edit /boot/firmware/extlinux/extlinux.conf and add extra kernel parameters there on the line that starts “append”

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Are you using an Active miniDP adapter? Passive adapter will not work…


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Umm, that can be the reason. The adapter i bought is this one, and there is written nothing about active/passive.

Do you have any brand/model tested working to reccomend ?

We’ve been using this model:

i’m sure there are other models, but yeah that’s the only one i’ve tested so far…


Thank you Robert,
the only one i can have delivered to me tomorrow is this, I will let you know if it works as well . If it doesn’t i will stop the necessary time and stick to the model you tested.

. the active miniDP → HDMI arrived
. it is a half-success story
. the monitor Elecrow 5’ works
. the monitor Magedonk 7’ does not work. In the sense that

  1. I off the BBAI64
  2. I connect the monitor and power (usb) plug to the BBAI64
  3. power on to BBAI64
    => Continuous reboot of the system

for me 1 screen working is enough for the moment :wink:

do you have a model number for this one?


. The monitor model is T080A
. I made a further test connecting also an external power source, now IT WORKS.
. maybe the reboot was due too much power drawn out of the BBAI64

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