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 Post subject: 240p via HDMI on Raspberry Pi to RGBS, no need for RGB hats!
PostPosted: Wed Jul 03, 2019 8:19 pm 



Joined: 14 Aug 2017
Posts: 456
Editing this first post to point out that it is far, FAR better to simply use CEA 8 as the global video mode (on the config.txt file). I think the person who wrote the guide linked below got it wrong. All you need in the config.txt file is:

---

hdmi_group=1
hdmi_mode=8


hdmi_ignore_edid=0xa5000080
hdmi_pixel_encoding=2
avoid_safe_mode=1
disable_overscan=0
config_hdmi_boost=4
hdmi_drive=2
hdmi_group=1
hdmi_mode=6

kernel=zImage
hdmi_force_hotplug=1
gpu_mem_256=128
gpu_mem_512=256
gpu_mem_1024=512

dtparam=audio=on

---

Some of those non-bold entries may not be necessary but they don't seem to hurt.
No need to use the hdmi_cvt setting at all. It just causes problems in some systems like the Genesis. Recalbox is also still what I recommend the most for this setup since different video modes can be set in the recalbox.conf file (which can be in the USB drive for easy changes) for the front end/ES, for Kodi, and for individual cores and games. So the menu and Kodi can be 480i (DVDs!), as CEA 6 HDMI. Perhaps this is also possible on Retropie. The global.videomode setting in this .conf file should also be set to CEA 8 HDMI (global.videomode=CEA 8 HDMI).

And of course you'll want to set integer scaled custom aspect ratio. No need to mess around with CRTSwitchres. It's more manual adjustment without the super resolution, but a cvt with the super resolution can be set on a per-core basis anyway (or vice versa, could use the old config below and set CEA 8 only for systems that don't work well with the former).

Original post:
Spoiler: show
With the Raspberry Pi 4's release, I thought it would be useful to post here about something that I have to conclude is not widely known. It turns out that CRT users (and I suppose OSSC users also) can very easily obtain real 240p RGB analog output from a Raspberry Pi's HDMI out without the need for analog RGB hats. Instead, the digital (HDMI) to analog conversion can be done easily with devices that have a lower cost, and that you may already own. HDMI 240p RGB output uses the same method that RGB hats rely on, that is, by adding a few entries in the RBP's config.txt file.

After configuring the config.txt file (see below), all that is needed is to connect the RBP's HDMI output to an HDMI-VGA converter (the often-recommended cheap Tendak dongle, for example), which can then be connected to any device that can combine sync to attain RGBS (or RGsB). Besides the better-known RGB interfaces, there are many other low-cost Extron devices that can pass through the RGB signal while outputting the required sync (many can also output component, for use with consumer CRT TVs). As an additional advantage, this approach can preserve digital audio if it is extracted (via an HDMI switch or audio extractor) before the DAC. Yet another advantage is not having to rely on custom images supplied by the RGB hat sellers.

My own setup is RBP3+ HDMI -> Digital audio extracted by HDMI switch -> HDFury3 -> Extron Rxi 203 -> RGB switch -> BVM

Like with the RGB hats, you will want to turn off bilinear filtering, set integer scaling, etc., on the image/emulator that you use to get an accurate 240p picture. Setting a "super resolution" of 1920 is ideal.

The required config.txt settings are the following:
hdmi_cvt=1920 240 60 1 1 0 0
hdmi_ignore_edid=0xa5000080
hdmi_pixel_encoding=2
avoid_safe_mode=1
disable_overscan=0
config_hdmi_boost=4
hdmi_drive=2
hdmi_group=1
hdmi_mode=6

kernel=zImage
hdmi_force_hotplug=1
gpu_mem_256=128
gpu_mem_512=256
gpu_mem_1024=512

dtparam=audio=on
boot_delay=3
Source: https://github.com/recalbox/recalbox-os ... I-(EN) (more information, in particular what each of the entries does, can be found there also). I suspect that not many people find this page because the Recalbox wiki has the wrong link for it in its manual.

Do take note of the hdmi_mode=6 entry. HDMI mode 6 (CEA group) is 480i, which is active only for the frontend (EmulationStation, Retropie, etc.) to make it legible. Retropie may not need it, and if you hate 480i you can remove this entry or change it to mode 12 (240p). More info on HDMI modes here: (https://www.raspberrypi.org/documentation/configuration/config-txt/video.md). Furthermore, specific core overrides can be set to use yet another video mode (such as 480p for, say, retro PC games), though how this is done varies by the image used (on Recalbox, for example, this is done in the recalbox.conf file). I also recommend setting the frontend's global video mode to prevent temporary transitions to the default 720p, when using some images, when loading cores. The mode should be set to either 480i or 240p (remember that the monitor itself does not distinguish between these two).

The same settings should also work with Retropie and Lakka. I tested it on both and only had problems (random black screens) with Lakka, though it may have just been a bad image.

I imagine that the RBP4 will allow Retroarch to fully support CRT SwitchRes. As far as I can tell it does seem to work on current RBP3s too with the above config, though I've seen some claim that it's not supposed to, but setting the integer scale manually is always possible anyway. These HDMI video mode settings should be the same on the RBP4, and so before people spend money on new hats that are likely to come out for the RBP4 I would suggest giving this method a try first. If you try to set this up and encounter any problems I'll try to help.


Last edited by fernan1234 on Tue Jul 09, 2019 4:24 am, edited 3 times in total.

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 Post subject: Re: 240p via HDMI on Raspberry Pi to RGBS, no need for RGB h
PostPosted: Wed Jul 03, 2019 9:10 pm 


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Joined: 06 Mar 2006
Posts: 11729
Location: Germany
Quote:
My own setup is RBP3+ HDMI -> Digital audio extracted by HDMI switch -> HDFury3 -> Extron Rxi 203 -> RGB switch -> BVM

if digital audio isn't a requirement, the HDMI to component converter that Mike Chi recently recommended works fine as well.

Pi 3 > HDMI to YUV+analogue Audio box ($20) > BVM + speakers.


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 Post subject: Re: 240p via HDMI on Raspberry Pi to RGBS, no need for RGB h
PostPosted: Wed Jul 03, 2019 9:22 pm 



Joined: 14 Aug 2017
Posts: 456
Fudoh wrote:
if digital audio isn't a requirement, the HDMI to component converter that Mike Chi recently recommended works fine as well.


This would be fine too. The route I went over is better for keeping it all RGB. Either way analog audio can also be taken from the DAC.

I also forgot the case of PC CRTs, which can use the HDMI->VGA route too, but without the need for a sync combiner. Would just need to set 480p as the output and then use the interlace shader on Retroarch to get something pretty close to real 240p.


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 Post subject: Re: 240p via HDMI on Raspberry Pi to RGBS, no need for RGB h
PostPosted: Wed Jul 03, 2019 10:22 pm 



Joined: 02 Mar 2017
Posts: 900
The Tendak has analog audio right on it too - so no need to extract elsewhere in my eyes (don't think I've ever used it, but the 3.5mm minijack is there!).


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 Post subject: Re: 240p via HDMI on Raspberry Pi to RGBS, no need for RGB h
PostPosted: Wed Jul 03, 2019 10:44 pm 



Joined: 14 Aug 2017
Posts: 456
Dochartaigh wrote:
The Tendak has analog audio right on it too - so no need to extract elsewhere in my eyes (don't think I've ever used it, but the 3.5mm minijack is there!).


It does and I'd bet it sounds fine. The ability to get digital audio when using the HDMI output is just another plus.


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 Post subject: Re: 240p via HDMI on Raspberry Pi to RGBS, no need for RGB h
PostPosted: Thu Jul 04, 2019 2:06 am 


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Joined: 09 Aug 2017
Posts: 1200
Location: Australia
Cant use the composite video output as sync?


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 Post subject: Re: 240p via HDMI on Raspberry Pi to RGBS, no need for RGB h
PostPosted: Thu Jul 04, 2019 2:16 am 



Joined: 14 Aug 2017
Posts: 456
Syntax wrote:
Cant use the composite video output as sync?


I would think not, since to get composite out it's necessary to enter an sdtv_mode in the config.txt file, which would conflict with the hdmi_mode set there. If it were possible it would be a nice convenience, but cheap Extron units that can do RGBHV -> RGBS can be found for less than $20, and often serve other functions, so I'd go with one of those regardless.


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 Post subject: Re: 240p via HDMI on Raspberry Pi to RGBS, no need for RGB h
PostPosted: Thu Jul 04, 2019 2:30 am 


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Posts: 1200
Location: Australia
Id imagine a simple diode combiner would work for a dirty quick fix.


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 Post subject: Re: 240p via HDMI on Raspberry Pi to RGBS, no need for RGB h
PostPosted: Thu Jul 04, 2019 4:14 am 



Joined: 18 May 2017
Posts: 560
It's been done...

Check out the RaspberryJAMMA

https://arpicade.com/
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 Post subject: Re: 240p via HDMI on Raspberry Pi to RGBS, no need for RGB h
PostPosted: Thu Jul 04, 2019 4:51 am 



Joined: 01 Jul 2017
Posts: 30
I also just tried and can second that the $12 component converter works great. A huge advantage of the HDMI output is that it can do 480i whereas the DPI port can only do progressive outputs.

I'm also able to output 240p super resolution via the same adaptor on an Intel IGP as well as a Quadro K1200.


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 Post subject: Re: 240p via HDMI on Raspberry Pi to RGBS, no need for RGB h
PostPosted: Thu Jul 04, 2019 7:41 am 


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Location: Florida
I have this running on recalbox,but I use just a hdmi to vga,then I made a vga scart cable and going to my rgb modded crt.


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 Post subject: Re: 240p via HDMI on Raspberry Pi to RGBS, no need for RGB h
PostPosted: Fri Jul 05, 2019 7:34 pm 


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Joined: 15 Oct 2015
Posts: 125
Location: Salem OR
fernan1234 wrote:
With the Raspberry Pi 4's release, I thought it would be useful to post here about something that I have to conclude is not widely known. It turns out that CRT users (and I suppose OSSC users also) can very easily obtain real 240p RGB analog output from a Raspberry Pi's HDMI out without the need for analog RGB hats. Instead, the digital (HDMI) to analog conversion can be done easily with devices that have a lower cost, and that you may already own. HDMI 240p RGB output uses the same method that RGB hats rely on, that is, by adding a few entries in the RBP's config.txt file.

After configuring the config.txt file (see below), all that is needed is to connect the RBP's HDMI output to an HDMI-VGA converter (the often-recommended cheap Tendak dongle, for example), which can then be connected to any device that can combine sync to attain RGBS (or RGsB). Besides the better-known RGB interfaces, there are many other low-cost Extron devices that can pass through the RGB signal while outputting the required sync (many can also output component, for use with consumer CRT TVs). As an additional advantage, this approach can preserve digital audio if it is extracted (via an HDMI switch or audio extractor) before the DAC. Yet another advantage is not having to rely on custom images supplied by the RGB hat sellers.

My own setup is RBP3+ HDMI -> Digital audio extracted by HDMI switch -> HDFury3 -> Extron Rxi 203 -> RGB switch -> BVM

Like with the RGB hats, you will want to turn off bilinear filtering, set integer scaling, etc., on the image/emulator that you use to get an accurate 240p picture. Setting a "super resolution" of 1920 is ideal.

The required config.txt settings are the following:
Spoiler: show
hdmi_cvt=1920 240 60 1 1 0 0
hdmi_ignore_edid=0xa5000080
hdmi_pixel_encoding=2
avoid_safe_mode=1
disable_overscan=0
config_hdmi_boost=4
hdmi_drive=2
hdmi_group=1
hdmi_mode=6

kernel=zImage
hdmi_force_hotplug=1
gpu_mem_256=128
gpu_mem_512=256
gpu_mem_1024=512

dtparam=audio=on
boot_delay=3

Source: https://github.com/recalbox/recalbox-os ... h-HDMI-(EN) (more information, in particular what each of the entries does, can be found there also). I suspect that not many people find this page because the Recalbox wiki has the wrong link for it in its manual.

Do take note of the hdmi_mode=6 entry. HDMI mode 6 (CEA group) is 480i, which is active only for the frontend (EmulationStation, Retropie, etc.) to make it legible. Retropie may not need it, and if you hate 480i you can remove this entry or change it to mode 12 (240p). More info on HDMI modes here: (https://www.raspberrypi.org/documentati ... t/video.md). Furthermore, specific core overrides can be set to use yet another video mode (such as 480p for, say, retro PC games), though how this is done varies by the image used (on Recalbox, for example, this is done in the recalbox.conf file). I also recommend setting the frontend's global video mode to prevent temporary transitions to the default 720p, when using some images, when loading cores. The mode should be set to either 480i or 240p (remember that the monitor itself does not distinguish between these two).

The same settings should also work with Retropie and Lakka. I tested it on both and only had problems (random black screens) with Lakka, though it may have just been a bad image.

I imagine that the RBP4 will allow Retroarch to fully support CRT SwitchRes. As far as I can tell it does seem to work on current RBP3s too with the above config, though I've seen some claim that it's not supposed to, but setting the integer scale manually is always possible anyway. These HDMI video mode settings should be the same on the RBP4, and so before people spend money on new hats that are likely to come out for the RBP4 I would suggest giving this method a try first. If you try to set this up and encounter any problems I'll try to help.
If only I read this a week ago. Anyhow I'm going for a rpi4+retrotink ultimate combo to a consumer crt. There seems to be an early lakka build that works for pi4 already.

No word yet on retropie release for the pi4 yet.

Sent from my SAMSUNG-SM-G891A using Tapatalk
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 Post subject: Re: 240p via HDMI on Raspberry Pi to RGBS, no need for RGB h
PostPosted: Fri Jul 05, 2019 10:00 pm 



Joined: 14 Aug 2017
Posts: 456
Well the retrotink makes for a leaner setup especially for component, so it has that going for it. It'd be interesting to compare it to an HDMI-to-component converter that's a third of its cost though.


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 Post subject: Re: 240p via HDMI on Raspberry Pi to RGBS, no need for RGB h
PostPosted: Fri Jul 05, 2019 11:02 pm 


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Posts: 125
Location: Salem OR
I have both, one thing I like about the retrotink is that it has s-video output. HDmi to svideo isn't very common from what I have seen

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DC,Xbox,SS,GEN32XCD,SNES,N64>Samsung 55Q8FN
3DO,360,Wii>SONY 34XBR910


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 Post subject: Re: 240p via HDMI on Raspberry Pi to RGBS, no need for RGB h
PostPosted: Sat Jul 06, 2019 6:22 pm 



Joined: 14 Aug 2017
Posts: 456
A couple of tips for Lakka:
-Change the menu driver to rgui, as xmb will be almost inoperable in low res (and turn off menu bilinear filtering in the user interface menu).
-It looks like Lakka (and Retropie) will use 480i across the board with the config in OP, so you'll want to set hdmi group to 2 (DMT) and mode to 87 (the custom mode), or try group 1 (CEA) and mode 8 (280p).
-Turn on CRTSwitchres on the video settings if you get a very horizontally squished picture (and set super resolution to 1920).

Be careful when using this with Lakka though because multiple times my SD image got corrupted after making these changes and putting it back into the RBP, so if you want to try I suggest having a backup of your image. More generally I'd just recommend staying with Recalbox or Retropie for this 240p config.


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 Post subject: Re: 240p via HDMI on Raspberry Pi to RGBS, no need for RGB h
PostPosted: Mon Jul 08, 2019 11:00 pm 


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I'm definitely behind here. Are we saying to buy this guy and with the right config we can get to 240p/component/CRT?

https://www.ebay.com/itm/New-HDMI-to-5R ... 3156028580


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 Post subject: Re: 240p via HDMI on Raspberry Pi to RGBS, no need for RGB h
PostPosted: Mon Jul 08, 2019 11:53 pm 



Joined: 14 Aug 2017
Posts: 456
When I tried a couple of those cheap made-in-China HDMI-Component boxes (not for this, but for HD stuff) they all seemed to perform about the same.

Edit: will be making an edit to OP. I discovered that simply setting CEA 8 as the video mode is by far better than using the custom video timing (cvt) setting.


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