switch + vga converter no signal after switching

[nopeva]

Hi All,

I have a switch to share my monitor, keyboard and mouse and have set hdmi_force_hotplug=1 and hdmi_boost=7 in the config.txt file in order to increase the signal sent to the monitor. My rpi3 is connected to the switch through a hdmi to vga converter and it is working as expected when the rpi3 boots.

When I switch to the other screen it works as well, however, if I try to get back to pi's screen then get message "no input signal". I have tested different configs but I should be missing something since it always works well when it boots. Please note that I can switch to the other screen back and forth without any trouble.

Many thanks for your help.

[Ernst]

Hi All,

I have a switch to share my monitor, keyboard and mouse and have set hdmi_force_hotplug=1 and hdmi_boost=7 in the config.txt file in order to increase the signal sent to the monitor. My rpi3 is connected to the switch through a hdmi to vga converter and it is working as expected when the rpi3 boots.

When I switch to the other screen it works as well, however, if I try to get back to pi's screen then get message "no input signal". I have tested different configs but I should be missing something since it always works well when it boots. Please note that I can switch to the other screen back and forth without any trouble.

Many thanks for your help.

This is very likely a problem caused by your switch. What is already suspicious is that you need to boost the signal. I am using a similar setup with an Aten CS84U switch, which is quite affordable because it comes with 4 cables, with all 4 ports connected to three x Windows and 1 x Raspberry Pi 3.
For historic reasons I am using VGA on all Windows machines, for the Raspberry Pi 3 I am using a "cheap" HDMI to VGA adapter that I got from Ebay for €6,79
I have not seen any evidence that the clients are affected when switching, it just simply works.
The only "problem" I have noticed is that the Pi does not really like hot-plugging the mouse/keyboard USB connection, but that is acceptable.

[nopeva]

Thank you for your reply. I think that the switch works well, it works with a laptop or a pc.The boost option in fact is just another configuration I tested but it works without it as well. The trouble is just when switching back to the pi only.

[Ernst]

What switch are you using ? A mechanical or an electronic switch ?
Can you give more information on the make / model of the switch ?

[nopeva]

It's this a UGREEN Conmutador Switch KVM USB VGA 1080P, 2 entradas de VGA y USB, 1 salida de VGA .

[Ernst]

It's this a UGREEN Conmutador Switch KVM USB VGA 1080P, 2 entradas de VGA y USB, 1 salida de VGA .

That looks like a simple low cost KVM, it is very possible that this device does not emulate a display when switched to another channel. What you could try are changes described in this thread viewtopic.php?f=28&t=17354&p=173430 but I can not guarantee that this will solve the problem.

[nopeva]

Thanks for the link unfortunately it does not work in my case.

The switch is a low cost one but it works with any combination of pcs/laptops I have so it seems that the problem is related to the pi. In fact it seems to be related to the power/strength of the video signal which must be insufficient to switch back but I don't understand is why it works on boot since the signal sent to the monitor should be the same...

[Ernst]

Have you considered the signal sent from the monitor to the Pi might be the problem ?
What you could try is to use ssh to connect to the Pi from your computer and look at the log files when the output disappears.

[nopeva]

Thanks again for your suggestions. I have tried in three different monitors and 2 different vga cables but the problem is still the same. I am running out of ideas.

[Ernst]

Have tried to connect the Pi directly to the monitor and then see what happens when you remove/replug the VGA cable. If this works then the problem must be the switch.

[nopeva]

I have tried to plug the pi directly to the monitor and then unplug but it does not work so it seems that the switch is not the problem. Therefore the problem might be either the hdmi to vga converter or the pi.

[FTrevorGowen]

What does tvservice -n and tvservice -s report from the HDMI-to-VGA adapter when it's connected/switched to the monitor or disconnect/unswitched? (assuming you can remotely SSH/login to your Pi when doing the latter). Some HDMI-to-VGA converters do not pass through all of the monitors info. - see my notes here: http://www.cpmspectrepi.uk/raspberry_pi ... tings.html
(and very basic VGA switches may not even have the DDC connection:
http://www.cpmspectrepi.uk/raspberry_pi ... tches.html
but I don't think that's your issue)
Trev.

[nopeva]

Thanks for your reply. I do not have access through ssh but after booting the output of these commands is:
device_name=HWP_HP_S2231

state 0x12000a [HDMI DMT (82) RGB full 16:9], 1920x1080 @ 60.00Hz, progressive

[FTrevorGowen]

Thanks for your reply. I do not have access through ssh but after booting the output of these commands is:
device_name=HWP_HP_S2231
state 0x12000a [HDMI DMT (82) RGB full 16:9], 1920x1080 @ 60.00Hz, progressive

Ok. Does that name look anything like your display's name/model/number? (If not, then it's possibly that of the converter and, if so, could mean that only partial information from the display is being passed back)
You may find the output's of tvservice -m DMT and tvservice -m CEA of interest eg. is the above state a preferred or native mode?
Trev.

[nopeva]

Thanks again, these commands are very helpful.

Yes, the monitor is recognized and I have just changed it to be in native mode. However, I still get the same problem, if I do not switch it works, after switching it does not (the video signal is lost for the pi but it is not for the laptor or pc).