Hardware Testing Wiki Page

[anthonycaccese]

I added a draft hardware testing wiki page with an initial structure to document known working configurations for each Raspberry Pi Board + TV output type (either CRT or Modern)

https://github.com/anthonycaccese/240-MP/wiki/Hardware-Testing

Idea being that we can add as many methods that we find working for each board plus output type.

As an example; if someone had a working configuration for RGB out to a CRT on the Raspberry Pi 3b+, we would add an additional method under Raspberry Pi 3b+ >> CRT Output.

If you have a working configuration that isn't noted on the above page yet please add it as a comment to this message with the following information:

• Cable (or hardware used): Please be as detailed as possible. For example, if your setup required a HDMI to VGA converter + VGA cable + SYNC combiner, please list each (and if possible provide links to each as well)
• Configuration Details (config.txt + any other changes to things like cmdline.txt or EDID configuration)

I won't be able to test every provided method so please try to be as detailed as possible to help others that may want to try your setup.

Thank you
-Ant

[butterrsoft]

Pi5 on 15kHz CRT at 480i via HDMI-to-VGA :D

[anthonycaccese]

thank you! I added the link to your detailed write up here: https://github.com/anthonycaccese/240-MP/wiki/Hardware-Testing#crt-tv-output-3 as "method 2"

[bighomso]

i managed to get s-video output working to a NTSC crt via a VGA666 pihat running through a VGA to AV scaler.
to my surprise it worked pretty seamlessly and i didn't have issues getting video out through the adapter. lmk if there are any other details that would be helpful. theoretically this method should work with any scaler that converts VGA to another RGB but i don't have an RGB capable display so i can't speak to that. anyways here's what i got

Raspberry Pi 4

VGA / S Video / Composite via the VGA666 Pihat
• Target Resolution: 480i/576i
• Cable Used: Generic VGA and S-Video/Composite
• Devices Used: VGA666 Pihat adaptor (https://www.aliexpress.com/item/32801996414.html)
• VGA to AV Signal Adapter (https://www.aliexpress.com/item/1005005274323096.html)
• MPV video/decode params: not sure, same as default?
• Configuration Tested (config.txt):

# --- Global ---

arm_64bit=1
disable_fw_kms_setup=1
disable_splash=1
disable_overscan=1
dtparam=audio=on

# --- VGA666 Out --- 
dtoverlay=vga666
enable_dpi_lcd=1
display_default_lcd=1

# --- Pi 4B ---
[pi4]

# Drivers & Video
dtoverlay=vc4-fkms-v3d,cma-256
dtoverlay=rpivid-v4l2

# Overclocking
over_voltage=2
arm_freq=1750
gpu_freq=600


# --- Global ---
[all]
dtparam=spi=on
dtparam=i2c_arm=on
enable_uart=1
dtoverlay=w1-gpio

[anthonycaccese]

thank you @bighomso, I very much appreciate the detail! I added this just now with credit to you: https://github.com/anthonycaccese/240-MP/wiki/Hardware-Testing#crt-tv-output-2

And yup if you aren't specifically changing the video/decode settings then its using default.

[animelighthouses]

@bighomso Thanks for this; I am planning on giving it a try. Could I ask how you are connecting audio since, as I understand it, VGA (and therefore S-Video via VGA) is video only. Are you using the typical Pi AV cables in addition to VGA/S-Video but only connecting the red and white AV cables?

[bighomso]

@animelighthouses oh that’s a good point i forgot to mention audio! i’m using an audio only 3.5mm to RCA cable. you could use the pi video cables if you have them but i have plenty of the red and white RCA’s around so i don't need to.
i have an unfortunate update with the S-video adapter. i don’t know if it’s this particular unit or if there’s something wrong with the product in general but the S-video signal is a lot dimmer and seems to have some colour inaccuracies. the composite output looks great and i’m still using the adapter because it fixes some other issues i was having but using composite kind of defeats the point of the whole thing.
Retrocastle had a slightly more expensive VGA—S video adapter that i should have bought but i went with the cheaper version and… well i guess you get what you pay for.

[animelighthouses]

@bighomso Great, and thank you for the (unfortunate!) update. It’s helpful in setting expectations when I give this a go and still good to know that the VGA output in general works with this method.

I have seen the more expensive VGA to S-Video/ AV adapters and I may end up getting one. Although I intend to explore if VGA to RGB SCART might be a workable option before that.

[bad1dea]

Pi 4 - true progressive 240p/288p over composite (3.5mm A/V jack), full KMS

Wanted to share a setup that gets genuine progressive 240p/288p out of the Pi 4's composite output under the full vc4-kms-v3d driver (not the FKMS path used in the tested config above). Mainly wanted RetroArch/emulator-style rendering to actually be progressive, not interlaced.

Hardware

• Raspberry Pi 4B
• Adafruit composite A/V cable (3.5mm TRRS → RCA)
• Standard CRT TV

OS / kernel

• Raspberry Pi OS Lite (64-bit), Trixie
• Kernel 6.18.34+rpt-rpi-v8 (current default as of writing)

The catch: the stock vc4-kms-v3d driver doesn't have a progressive 240p mode sized for a normal 720x480 framebuffer, only interlaced 480i/576i, or a true 240/288-line mode that's awkward for normal-sized UI/video content. Ended up patching vc4_vec.c/vc4_plane.c to add a "720x480 (scaled)" mode (normal-canvas framebuffer, hardware-scanned out as real progressive 240p), plus a fix so video players don't silently fall back to interlaced when they grab their own DRM master for playback. This hit MPV specifically: it defaults to whatever mode is flagged "preferred" on the connector if you don't pass an explicit mode, which was still the interlaced one.

config.txt (relevant lines):

dtoverlay=vc4-kms-v3d,composite=1
disable_fw_kms_setup=1
disable_overscan=1
disable_splash=1
dtparam=audio=on

cmdline.txt (append):

video=Composite-1:720x480@60e

Repo with the patch, full write-up of the why (including a system hang I hit trying to force the mode via --drm-mode= from a second DRM client, which turned out to be an existing vc4 driver issue independent of this patch, not something it introduced), build instructions, and a CI job that publishes a prebuilt module matching whatever kernel Raspberry Pi OS currently ships:

https://github.com/bad1dea/linux (default branch: pi4-composite-240p)

Happy to help document this on the wiki if useful, or answer questions about the mode-selection fallback bug specifically. It'd affect anyone forcing a DRM mode from mpv/RetroArch on this driver, not just composite users.

[anthonycaccese]

thank you @bad1dea this is really helpful to read end to end. Wondering if there would be any interest for your patch to be accepted upstream? Either way I am glad you've implemented it and wrote up helpful instructions for others to use if they are looking for the same output format.

I've also been thinking about moving from vc4-fkms-v3d to vc4-kms-v3d. The main reason i started with vc4-fkms-v3d is I was struggling to get audio to work consistently over the kms and for some reason on fkms it just worked so I took that as a win and went with it =) I've had it my list to go back to and try to figure out why but just haven't had the moment to do so.