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

[2Dsx]

Hello everyone.
Before writing, I clarify that I do not buy any kit, I assembled it on my own, buying the resistances and mounting it on a protoboard.
Everything works perfect, except that gradients look weird.
The pure colors look perfect, when combining colors it looks like saturated, I attach images so that you understand what I'm talking about: https://imgur.com/a/pUodiQb.
I am using resistances of 5% tolerance, and I read in the manual that the 500 Ohms should be as close as possible, in this case I am using 470 Ohms, this interferes? Somebody could help me? I would appreciate it very much, greetings!

[Burngate]

I'm not sure what you mean by "gradients look weird", and your picture doesn't help me.

However, if you use non-ideal resistor values then, on a ramp from black to full red/green/blue, the 63 steps won't be identical in size.

The ideal resistor value should be 500R and Gert recommends 1%. That means anywhere from 495R to 505R
470R is 6% low, and so a 5% resistor could be 11% low (though may not be). However, you could add a 30R resistor in series if you want to be more accurate.

[Alex_321]

Is compatible Gert VGA 666 adapter with the last model Raspeberry Pi 3b+? Can I use this adapter to manage 320x240 resolution? Can I use this adapter in O.S as Lakka, Recalbox or Retropie?

Greetings.

[igcek]

Hi,

i assembled and played with gert666 allmost from the beggining. So i remember that then you had to also change bt-blob but as it progressed all you had to do is add couple of lines to config.txt.

Yesterday i started playing with it again and it doesnt work. I used 2 different gert666 connectors that on old version work and i did exacly as it sais in the how to on the first post. What i want to know is, has support for gert666 been removed from new raspbian (2018-11-13-raspbian-stretch-full.zip)? Can anybody try the new version just to see that its not only me. And if anybody could point me to the last version of raspbian that works.

Thank you very much
igcek

[unbannable]

Got this successfully working as a second monitor but now I have the problem with the vga cable, everything has fuzzy lines over the screen, I have one cable that is 95% okay. So has anyone bought a good vga cable that they can link?

[mrclean]

Having difficulty getting this working on a Raspberry Pi3B+.

My goal is to be able to use both HDMI out & Gert666 (vga) to display two different images simultaneously.

So far I have confirmed the GERT666 works independent from the HDMI output & vice versa, I simply cannot get them to work simultaneously together to display two different images or even the same image at the same time. Does anyone see anything obvious with the below settings ?! Again my HDMI out works fine / cable is fine / monitor is fine. The gert666 adapter works, the cable is fine, the 2nd monitor is fine.. I simply can't get them to work together.

These are my settings in Config.txt :

#Gert's VGA666
dtoverlay=vga666
enable_dpi_lcd=1
display_default_lcd=0

#Monitor Number 2
dpi_group=2
dpi_mode=16

[procount]

This is not surprising as supporting 2 monitors simultaneously (e.g extending your desktop as in Windows) is not supported readily out of the box.
There are a few programs that can be forced to use an alternative display (IIRC omxplayer, for example) but it is not many.

However, JamesH started creating some new firmware to facilitate this dual monitor function and is making good progress.
Please hop over to his thread here -> https://www.raspberrypi.org/forums/view ... 3&t=213854

Concerning your config.txt settings, the comments suggest that you expect the 2 sections to control 2 different monitors: VGA666 and "monitor number 2". However, the "monitor number 2" settings are also all related to the VGA666 adaptor, because they are for the dpi interface.

If you want to configure the hdmi settings, you need to additionally use hdmi_group and hdmi_mode.

[iWozza]

Hello,
I am trying to get the right dpi timings for a domestic widescreen CRT 16:9 PAL TV.
Using a variant of VGA666 called Pi2SCART from Arcade Forge
So far have managed to get it working using this:

gpu_mem_1024=256
disable_overscan=1
start_x=1
disable_splash=1
dtoverlay=vga666
enable_dpi_lcd=1
display_default_lcd=1
dpi_group=2
dpi_mode=87

hdmi_timings 320 1 20 29 35 224 1 10 14 16 0 0 0 50 0 6400000 1

gpu_mem_256=112
sdtv_aspect=3
sdtv_mode=2
gpu_mem_512=144
hdmi_pixel_encoding=2
dtoverlay=lirc-rpi
dtparam=gpio_in_pin=18
dtparam=gpio_out_pin=17

It's OK but...
Guess it is fine for 240p retro gaming but I want to watch movies in OSMC
The resolution is not enough for reading text menus and the video quality is too pixelated.

Ideally I need PAL 576i but I was told Interlaced is not supported on the GPIO's....?

I would just settle for full 576p.... or even 480p
PAL widescreen might be 1024x576 but it is confusing because of stretch pixels or something.
I tried changing the numbers but only get crazy, wavy lines I don't understand the dark art of CRT blanking frames.

Tried most of the #preset timing in the forum guides but had no luck except the one above

Help much apreciated

[antiriad]

Hello,
it is technically possible to set a custom resolution of 320x200 on VGA666?
Thanks

[Laur3nc3]

I purchased this vga666 and it works with the config file edit.
I can also see the resolution as good as it can get for the screen I have.
I have need though to use dual screen with this using HDMI and VGA. This was the purpose of my purchase
Has anyone figured out how to do this from
https://github.com/fenlogic/vga666/blob ... manual.pdf

Please help me and others who need this also
#dualscreen

[rpdom]

I purchased this vga666 and it works with the config file edit.
I can also see the resolution as good as it can get for the screen I have.
I have need though to use dual screen with this using HDMI and VGA. This was the purpose of my purchase
Has anyone figured out how to do this from
https://github.com/fenlogic/vga666/blob ... manual.pdf

Please help me and others who need this also
#dualscreen

Currently only certain applications can use dual screen, such as omxplayer where you can select which screen you want the video output to be displayed on. Running two copies of omxplayer can display videos on both screens. JamesH (forum moderator and Raspberry Pi Software Engineer) is working on something that will allow dual screens to be used with the desktop. From what I understand there are only a few more bits to sort out before that will be released. I have no idea about timescale.

[OdinsCat]

I find just hooking a VGA to HDMI adapter from the store handles all the jobs well unless this is for multiple monitors?

[OdinsCat]

Oh wait it's for dual screeen? Sorry?

[rpdom]

Oh wait it's for dual screeen? Sorry?

That's correct. Currently you can only have the desktop on one screen, but you can use some software like omxplayer to play videos on the other screen at the same time. Jamesh's work will allow the desktop to be used on two screens, either using Gert's adaptor or with the official 7" touch screen as well as HDMI.

[FreZeeN]

a simple question:

is the new pi4 compatible with vga666?

[mahjongg]

a simple question:

is the new pi4 compatible with vga666?

Yes!

[gittubaba]

Can anyone tell me (or direct me to some spec) about the DAC conversation timing? Using a resistor network will be very fast but its hard to find accurate and multiplier value resistors. I'm thinking about using three DAC0808. According to Datasheet its 150 ns. Is that okey for vga?

[Gert van Loo]

Let's assume a low quality screen like VGA: 640x480 at 30 FPS. Disregarding any blanking time the pixel frequency would be 9MHz which is 108.5 nsec.
So NO, 150ns is too slow. (Unless you wan to fall back even further to CGA)

A modern resolution screen like 720p50 would require (1280+370)x(720+20)x50 = 61.8 MHz which needs a conversion time of ~16ns . So ten times faster then what you have.

[gittubaba]

Thank you very much for the explanation. I'll discard the DAC0808 idea and use resistors. I'll try two in series to make the correct value, ex: 3.3K+680 = 4K, 6.8K+1.2K = 8K etc.... If i don't find exact 2K,4K,8K etc.. values.

[Limulf]

Hi everyone,

I have been trying, without success, to use three monitors at the same time with a Pi 4 (4Gb), plugging them to both HDMI ports and to the Gert VGA adapter. I started from the configuration found here, but I only manage to get output from the main HDMI output, and the VGA adapter:

Code: Select all

framebuffer_width=800
framebuffer_height=600
dpi_group=2
dpi_mode=24
dtparam=i2c_arm=off
dtparam=spi=off
dtparam=uart0=off
dtparam=uart1=off
dtoverlay=pi3-disable-bt-overlay
dtoverlay=vga666
enable_dpi_lcd=1
display_default_lcd=1
force_pwm_open=0
dtparam=audio=on
start_x=1
gpu_mem=128

Is what I want possible? Could someone provide any information, or where to look for it?

Thanks and best regards,
Juan.

Edit: Thanks for your reply, mahjongg

[mahjongg]

The RPI4 can only support two frame buffers (displays) simultaneously, not three. So the VGA666 simply uses one of the frame buffers of a HDMI port.

[azbest]

I just tried buster on my RPi2 with a GertVga666. It works.
Also It seems the max_framebuffers=2 is very usable in case of dual display for this hw also, not just for Rpi4.

I also got fuzzy lines in the output like you can see in this video
https://www.youtube.com/watch?v=5f5hpGrPpZk
Not sure if it is "normal" or hw/sw bug in my case.

[antiriad]

Hello,
I have the same issue (flickering) with my RPi4 and VGA666.
I tried different video modes, config.txt options, cables and even another VGA666 but I still get a flickering picture.
No problem with my RPi3.

Any hint please?

EDIT: it seem to be related to software (Raspbian Buster) and not to hardware (RPi4).
is there a way to officially report this bug? Thank you

[Gert van Loo]

I have seen an 'issue' being raised on the github of the VGA666 adapter for this. I commented there and closed it as I know no solution, hardware wise, which can be done about it. The effect is called "bitcrawl" and has been present from the first version. It is mentioned in the assembly/installation manual.

[antiriad]

Hello Gert,
thank you very much for your feedback.
It was me that opened the issue on GitHub.

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?

Thank you