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MinecraftTom16
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Why wont hdmi work

Tue Dec 12, 2017 8:29 am

About 1&1/2 years ago I got the 7 inch touchscreen, and i really liked it. in fact im using it to put this on forum now. but just recently i tried to plug it into the hdmi tv again(the pi 3) but it didnt give a video output. this used to work, even after i had used the touchscreen, but now the pi boots up properly, but it doesnt give hdmi output. I know i can just edit the hdmi-force-hotplug thingy in config.txt, but i still want to use the touchscreen after, and i was wondering if there was a non-permanent way to make it work, like to work with both the official touchscreen and the tv/monitor. so is there any way I can make my pi3 running the latest raspbian stretch release(the one with the edited file explorer interface) work with both screens(not simultaneously)?

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DougieLawson
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Re: Why wont hdmi work

Thu Dec 14, 2017 11:49 am

When the RPF DSI touch screen is connected and powered up, the VC4 disables HDMI (unless you use the exceedingly experimental fkms or kms drivers).

It's one or the other with standard firmware driving the display.
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Re: Why wont hdmi work

Thu Dec 14, 2017 7:05 pm

DougieLawson wrote:
Thu Dec 14, 2017 11:49 am
When the RPF DSI touch screen is connected and powered up, the VC4 disables HDMI (unless you use the exceedingly experimental fkms or kms drivers).

It's one or the other with standard firmware driving the display.
Or one can simply not provide power to the touchscreen and the Pi will happily use a connected monitor instead.

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MinecraftTom16
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Re: Why wont hdmi work

Tue Jan 09, 2018 9:12 am

i disconnected the touchscreen from the pi, connected to the monitor but still doesn't work. is it maybe something to do with me using a HDMI to VGA adapter? :?:

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RaTTuS
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Re: Why wont hdmi work

Tue Jan 09, 2018 9:24 am

MinecraftTom16 wrote:
Tue Jan 09, 2018 9:12 am
i disconnected the touchscreen from the pi, connected to the monitor but still doesn't work. is it maybe something to do with me using a HDMI to VGA adapter? :?:
probably , power for that adapter or bad leads
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MinecraftTom16
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Re: Why wont hdmi work

Sat Jan 13, 2018 5:25 am

this adapter doesn't need external power, it doesn't have an external power plug

i edited the

Code: Select all

/boot/config.txt
so that it forces output through the HDMI, but now it wont work with the touchscreen. the adapter works now, but later i wont be able to use the 7" display.

180lifer
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Re: Why wont hdmi work

Fri Mar 02, 2018 6:43 am

I've built a tablet with the official display and am considering installing a toggle switch on the positive power lead to the display driver board so that the display can be disabled when I need HDMI.

I'll probably not switch the display off while the unit is powered up, but if a member of the Raspbian team reads these forums posts it sure would be nice to have an official method to toggle between displays without a reboot. It would be even nicer to be able to use both displays independently such that, for example, the touch screen could be used to drive a slide show displayed via HDMI.

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