HDMI and RISCOS


11 posts
by bucko0875 » Wed Jan 09, 2013 7:54 pm
My Pi hdmi works fine with the Wheezy os. But when using riscos, it will only boot with composite video. When I connect the hdmi adapter, it just sits there with a blank screen and won’t boot. Any suggestions?
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by DavidS » Wed Jan 09, 2013 8:50 pm
Did you boot with the HDMI plugged in?

On RISC OS Pi for some reason if you have HDMI plugged in on boot it uses only HDMI, an if you dn't it uses only Composite.
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by DavidS » Wed Jan 09, 2013 8:51 pm
I should qualify that to say at least with the RPi that I have (Model B v2 512MB).
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by DavidS » Wed Jan 09, 2013 8:57 pm
Also (just reread your initial post):
If you are using an adapter it probably draws power from the HDMI prort, and this does not work well with small low power boards such as the RPi. Perhaps the Linux driver is able to talk to the adaptor and tell it not to draw as much crrent.

If you are going from HDMI to DVI you do not need an adapter, you can just use a simple HDMI to DVI cable. This is because the RPi supports DVI moniters so there is no need to convert the signal.

If you are usin VGA/XGA then best of luck.
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by jfornango » Thu Jan 10, 2013 7:31 am
Running an Model B v3 and I noticed the video won't hot-swap either.
Not that it's a big deal, since the thing reboots in like 10 seconds. :lol:
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by DavidS » Thu Jan 10, 2013 1:04 pm
jfornango wrote:Running an Model B v3 and I noticed the video won't hot-swap either.
Not that it's a big deal, since the thing reboots in like 10 seconds. :lol:

The ploblem is the video device suport in RISC OS.
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by Burngate » Thu Jan 10, 2013 4:25 pm
Hot-swapping HDMI-composite doesn't work out of the box - it's chosen at boot time depending on whether HDMI is detected or not, before the kernel is loaded.

On your Wheezy image, what is the config.txt like? If you've added anything to make it work with your HDMI adapter, you should do the same for RISC OS

I'm assuming by HDMI adapter you mean a HDMI-VGA adapter. Those are problematic, because they don't seem to adhere strictly to the HDMI spec

You could try hdmi_safe=1 as a starting point, just to make sure things will work in a minimum configuration
After that, try hdmi_force_hotplug=1 (comment out hdmi_safe=1 or change to hdmi_safe=0)
Then see which modes and so-on your adapter will support
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by DavidS » Thu Jan 10, 2013 6:34 pm
I have just had the realization:
Why are you using an adapter when a DVI moniter + HDMI to DVI cable is a lot cheaper (at least from what I have seen). The cheapest HDMI to VGA adaptor that I have found cost $87USD, though the 21inch 1600x900 DVI capable HP monitor that I am using costs $50, add a $9USD cable and it is $59USD. And either way you are paying about $6USD Shipping.
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by pygmy_giant » Sat Jan 12, 2013 2:15 pm
works for me - £2 hdmi - dvi cable plus £12 dvi tft monitor from 2nd hand shop. No sound through DVI though so additional male-male 3.5mm jack plug lead also needed
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by DavidS » Sat Jan 12, 2013 2:32 pm
To add one question:
Is it possible to have both DVI/HDMI and Composite active at the same time? I have been playing with the CONFIG/TXT (actually CONFIG.TXT) for underclocking and video, though so far I have not been able to get it to enable composite and HDMI at the same time. Prefferably mirrored video, though it would also be nice to use each monitor seperately. I am asking this for testing of RISC OS applications primairily as low resolution looks better on an NTSC set.
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by Burngate » Sat Jan 12, 2013 4:41 pm
DavidS wrote:To add one question:
Is it possible to have both DVI/HDMI and Composite active at the same time? I have been playing with the CONFIG/TXT (actually CONFIG.TXT) for underclocking and video, though so far I have not been able to get it to enable composite and HDMI at the same time. Prefferably mirrored video, though it would also be nice to use each monitor seperately. I am asking this for testing of RISC OS applications primairily as low resolution looks better on an NTSC set.

Burngate wrote:.. it's chosen at boot time depending on whether HDMI is detected or not, before the kernel is loaded.

It's either-or. You can't have both. The GPU can't do both - neither the same nor different
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