How to debug video via ssh

Question

I have a Pi 2 model B and only access to an HDMI display, however I have not gotten any video output despite:

Having successfully booted RetroPie, pidora, NOOBS, and raspbian
Having tried every combination of hdmi_safe=1, hdmi_force_hotplug=1 and config_hdmi_boost=4
A multitude of HDMI cables

...so at this point I suspect there may be a legitimate hardware issue with the HDMI controller.

With some network monitoring I can manage to get the IP of the Pi when it appears on the network, so I can SSH in. I can even ssh -X in and get tuxeyes, but no xrandr. I'm not even sure how to get video device information without lspci working.

Does anyone know how to (via ssh) interact with the video device, or get any other kind of feedback that would provide information on the display system?

Try sudo tvservice -p – Dmitry Grigoryev Oct 21 '16 at 08:31 — Dmitry Grigoryev, Oct 21 '16 at 08:31

score 3 · Answer 1 · answered Apr 07 '17 at 20:55

I don't know if the following also works for Pi 2 model B (which is what your question is all about). But this works for my Pi 3:

I CAN start it without a HDMI-connected monitor attached, then plug it in, switch it on and activate HDMI:

Query the output status of HDMI:
```
sudo /opt/vc/bin/tvservice -s
```
Activate the monitor:
```
sudo /opt/vc/bin/tvservice -p
```
Monitor may stay black. However, you want it to display something on TTY console number 1, 2,... or 6. Use the chvt (change virtual terminal) command:
```
sudo /opt/vc/bin/tvservice -p; sudo chvt 1; sudo chvt 2; ...
```
Monitor black; you want to see the GUI. Again, use chvt and switch it to TTY console number 7:
```
sudo /opt/vc/bin/tvservice -p; sudo chvt 7;
```
Query monitor for supported CEA modes:
```
sudo /opt/vc/bin/tvservice -m CEA
```
Query monitor for supported DMT modes:
```
sudo /opt/vc/bin/tvservice -m DMT
```

Get more detailed info about the monitor:

sudo /opt/vc/bin/tvservice -d edid.dat
sudo /opt/vc/bin/edidparser edid.dat

Switch off the HDMI monitor:
```
sudo vcgencmd display_power 0
```
Switch on the HDMI monitor:
```
sudo vcgencmd display_power 1
```
Disable HDMI out:
```
sudo /opt/vc/bin/tvservice -o
```
Send keystroke to tty1 to wake up monitor:
```
sudo echo -ne "\033[9;0]" >/dev/tty1
```

score 0 · Answer 2 · answered Oct 21 '16 at 04:47

0

tvservice -s will show current status.

There is no man page but if you just type tvservice it will list the commands.

answered Oct 21 '16 at 04:47

Milliways

59,890
31
101
209

How to debug video via ssh

2 Answers2