vol.2
Posts: 26
Joined: Tue Dec 13, 2016 5:17 pm

Re: STICKY: Using a Gert VGA 666 adapter - [HOWTO]

Tue Nov 26, 2019 5:03 am

Gert van Loo wrote:
Tue Oct 08, 2019 6:25 pm
If this is a hardware-related problem, why does it happen only on Raspbian Buster and/or RPi 4, and not on Raspbian Stretch / RPi 3?
I don't know. Maybe they use a different drive strength for the GPIO or the Pi4 PCB has the tracks thinner and closer together. It can also be that there is more or different frequency noise on the supply. To trace things like this I would connect my spectrum analyzer to the signal and see if that show up anything different between the builds & PCB's.
Hi Gert, I wanted to report that I am getting zero visible dot crawl using this timing on a Pi4 with a 15kHz Sony CRT monitor:
320 1 16 30 34 240 1 2 3 22 0 0 0 60 0 6400000 1

I was playing around with timings because I'm trying to get various old dos programs to work in dosbox, but other timings showed dotcrawl. I think it may be a sweet-spot kind of situation with the pulse width and placement and not necessarily an issue with the sync voltage level. But, hey, I could be wrong.

kevinfishburne
Posts: 3
Joined: Sat Oct 12, 2019 12:33 am

Re: STICKY: Using a Gert VGA 666 adapter - [HOWTO]

Mon Jan 13, 2020 10:37 am

I was struggling for a while to get a super resolution working on a RPi4 with the RetroTINK (like a VGA666 but 24-bit/888). I finally got it working with these settings:

Code: Select all

# Turn off conflicting peripheral overlays using GPIO pins.
dtparam=i2c_arm=off
dtparam=spi=off
dtparam=i2s=off
dtparam=audio=off
enable_uart=0

# Generic 24-bit DPI display.
dtoverlay=dpi24
dpi_output_format=7

# Set default display.
enable_dpi_lcd=1
display_default_lcd=1

# Disable overscan.
disable_overscan=1

# Enable custom dpi timings.
dpi_group=2
dpi_mode=87

# Set custom dpi timings.
dpi_timings=3840 1 109 343 343 240 1 3 5 14 0 0 0 60 0 72925291 1 # 3840x240
#dpi_timings=320 1 9 29 29 224 1 21 3 14 0 0 0 60 0 6077108 1	# 320x224
I was connecting to a Sylvania CRT television over S-Video and noticed no dot crawl or artifacts in either of the above modes using both Lakka's November 4th nightly image and the latest Raspbian Buster Lite. Sadly I'm not sure if what fixed the initial issue was the above settings being correct or a firmware update.

Also of note here is that the holy grail of super resolutions, 3840x240, now works. Previously it would fail with a segfault on the RPi3. You may also find this spreadsheet useful for calculating dpi timings:

http://eightvirtues.com/lakka/hat/RPi%2 ... 20Docs.ods

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antiriad
Posts: 146
Joined: Sun Nov 17, 2013 7:38 pm
Location: Italy
Contact: Twitter

Re: STICKY: Using a Gert VGA 666 adapter - [HOWTO]

Mon Jan 13, 2020 11:00 am

kevinfishburne wrote:
Mon Jan 13, 2020 10:37 am
I was struggling for a while to get a super resolution working on a RPi4 with the RetroTINK (like a VGA666 but 24-bit/888). I finally got it working with these settings:
...
Hello Kevin,
may I ask if you are currently using this super-resolution with the CRT Switchres feature in LAKKA?

Thank you

kevinfishburne
Posts: 3
Joined: Sat Oct 12, 2019 12:33 am

Re: STICKY: Using a Gert VGA 666 adapter - [HOWTO]

Mon Jan 13, 2020 11:21 am

may I ask if you are currently using this super-resolution with the CRT Switchres feature in LAKKA?
I haven't played with that yet. I assume it changes the dpi timings to match the native output of systems without having to reboot. So far I've just been manually setting core overrides. My adventures with integer scaling haven't worked too well, as I still often have to set it manually and half the time it doesn't even integer scale properly on some game resolutions. You'd think integer scaling would just scale the whole thing to maximally fit within the "desktop resolution" / screen mode without clipping unless one resolution axis is larger than the screen mode axis (in which case it should center-clip), but it doesn't.

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antiriad
Posts: 146
Joined: Sun Nov 17, 2013 7:38 pm
Location: Italy
Contact: Twitter

Re: STICKY: Using a Gert VGA 666 adapter - [HOWTO]

Mon Jan 13, 2020 11:31 am

It seems that we are trying to achieve the same objective (but with not so good results by my side, with RPi4 and VGA 666)
Maybe you'll find interesting this thread on LAKKA forums:

https://forums.libretro.com/t/new-crtsw ... arch/20513

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