RGB to HDMI using a Pi Zero and a small CPLD

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IanB
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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by IanB » Mon Jun 08, 2020 8:28 pm

anightin wrote:
Mon Jun 08, 2020 4:19 pm
Much appreciated Ian, will do -- would most likely otherwise have found this out the hard way and then reaslised what they were for :lol:
I just noticed one other thing, You might have fitted P2 upside down on all four boards as I can see the 4 plastic 'pips' in the corners of each pin and they normally touch the pcb.
I can't tell for certain as the pin length isn't fully visible but, as mentioned on the wiki, the long end of the pins should go in the PCB and the short end will connect with the socket on the main board. When P2 is plugged into the main board, there should be no part of the pins visible, if you get a gap then they are upside down.

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by anightin » Mon Jun 08, 2020 9:42 pm

IanB wrote:
Mon Jun 08, 2020 8:28 pm
anightin wrote:
Mon Jun 08, 2020 4:19 pm
Much appreciated Ian, will do -- would most likely otherwise have found this out the hard way and then reaslised what they were for :lol:
I just noticed one other thing, You might have fitted P2 upside down on all four boards as I can see the 4 plastic 'pips' in the corners of each pin and they normally touch the pcb.
I can't tell for certain as the pin length isn't fully visible but, as mentioned on the wiki, the long end of the pins should go in the PCB and the short end will connect with the socket on the main board. When P2 is plugged into the main board, there should be no part of the pins visible, if you get a gap then they are upside down.
Thanks again Ian, that'll teach me for not reading the wiki properly :oops: , yes I assumed the long ends would be pointing up, will swap those over.

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by danielj » Fri Jun 12, 2020 4:24 pm

RM480Z anyone? (used the same settings as I calibrated on my Master).
capture2.png
d.

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by anightin » Fri Jun 12, 2020 6:11 pm

Dumb Question for those with ZX81 and/or other Sinclair machines.

Are you folk tapping into 5v internally to power the RGB to HDMI adapter or are you powering externally?

Just thought I'd do a quick poll.

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by IanB » Sat Jun 13, 2020 12:00 am

danielj wrote:
Fri Jun 12, 2020 4:24 pm
RM480Z anyone? (used the same settings as I calibrated on my Master).
Another one to add to the supported list :)
You can make a specific profile by copying and renaming the existing Master 128 profile in /profiles/xxx but change the Auto Switch option to off.

Also if that image was meant to be centred, it looks like the H & V Offsets in the geometry menu could do with a little tweak.
(Best to use a full screen coloured background and centre up the rectangle)

If you get a final profile, please post it and I'll add it to the next release.
anightin wrote:
Fri Jun 12, 2020 6:11 pm
Dumb Question for those with ZX81 and/or other Sinclair machines.
Are you folk tapping into 5v internally to power the RGB to HDMI adapter or are you powering externally?
It will likely work from internal power but I'm using an external PSU with my ZX80/81 and 48K Spectrum as it takes around 100-200ma and I'd rather not stress the 1amp 7805 regulators on those machines as they run hot enough already.

BTW I've added a new page to the wiki with cabling details for all supported machines:
https://github.com/hoglet67/RGBtoHDMI/wiki/Cables

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by aotta » Sat Jun 13, 2020 12:28 am

IanB wrote:
Sat Jun 13, 2020 12:00 am
BTW I've added a new page to the wiki with cabling details for all supported machines:
https://github.com/hoglet67/RGBtoHDMI/wiki/Cables
That's very useful, thank you!

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by anightin » Sat Jun 13, 2020 7:42 am

aotta wrote:
Sat Jun 13, 2020 12:28 am
IanB wrote:
Sat Jun 13, 2020 12:00 am
BTW I've added a new page to the wiki with cabling details for all supported machines:
https://github.com/hoglet67/RGBtoHDMI/wiki/Cables
That's very useful, thank you!
Ditto thank you! =D>

One other thing I noticed yesterday. I was running the HDMI via my upscaler which has HDMI in, and it is always reporting 60Hz input from the adapter despite the adapter menu being set to 1920x1080@50Hz

How did I manage to get the board stuck at 60Hz? Cycling the menu between 50 and 60 Hz and rebooting doesn’t seem to fix it. Might also explain why the genlock LED is always flashing too.

The output remains pin-sharp after calibration regardless of frequency on my monitor but it would be nice to resolve.

I have a 6bit issue 3 board with 20200504_d19df1c Release software.

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by IanB » Sat Jun 13, 2020 3:37 pm

anightin wrote:
Sat Jun 13, 2020 7:42 am
One other thing I noticed yesterday. I was running the HDMI via my upscaler which has HDMI in, and it is always reporting 60Hz input from the adapter despite the adapter menu being set to 1920x1080@50Hz
How did I manage to get the board stuck at 60Hz? Cycling the menu between 50 and 60 Hz and rebooting doesn’t seem to fix it. Might also explain why the genlock LED is always flashing too.
I have found that the Pi will sometimes not output the requested resolution or refesh rate if it thinks the EDID won't allow it.
Here are a couple of alternate 1920x1080@50Hz resolutions to try:

1920x1080@50Hz(Tests).zip
(419 Bytes) Downloaded 14 times

Unzip and put the files in the Resolutions folder on your Pi's SD card.
After rebooting you should have two new options to try:
1920x1080@50Hz(Test1)
1920x1080@50Hz(Test2)

Try both and see if they fix the issue.
If you get no output at all, hold down the menu button during reset to force the default@60Hz resolution.

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by anightin » Sat Jun 13, 2020 5:15 pm

IanB wrote:
Sat Jun 13, 2020 3:37 pm
anightin wrote:
Sat Jun 13, 2020 7:42 am
One other thing I noticed yesterday. I was running the HDMI via my upscaler which has HDMI in, and it is always reporting 60Hz input from the adapter despite the adapter menu being set to 1920x1080@50Hz
How did I manage to get the board stuck at 60Hz? Cycling the menu between 50 and 60 Hz and rebooting doesn’t seem to fix it. Might also explain why the genlock LED is always flashing too.
I have found that the Pi will sometimes not output the requested resolution or refesh rate if it thinks the EDID won't allow it.
Here are a couple of alternate 1920x1080@50Hz resolutions to try:


1920x1080@50Hz(Tests).zip


Unzip and put the files in the Resolutions folder on your Pi's SD card.
After rebooting you should have two new options to try:
1920x1080@50Hz(Test1)
1920x1080@50Hz(Test2)

Try both and see if they fix the issue.
If you get no output at all, hold down the menu button during reset to force the default@60Hz resolution.
Many thanks, I still get 1080p 60Hz output on both test files:
006C37F3-CBB4-46C6-99B4-F419D69DD0B3.jpeg
CBDA676B-05EB-4CDA-837F-9C88CE8E63E8.jpeg

Update: Just noticed that some of the resolution settings have a ". " in front of them, selecting a 50Hz mode without the dot fixes the issue. I wonder if this is my MacBook adding hidden files to the SD card or something?



In any case the 50Hz is now being selected and genlocking nicely.

So I guess the question now is, where are the ". xxxx" files coming from?

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by IanB » Sat Jun 13, 2020 5:28 pm

anightin wrote:
Sat Jun 13, 2020 5:15 pm
Many thanks, I still get 1080p 60Hz output on both test files:
What scaler is this?
I assume you are trying to use it in passthrough mode

Does the genlock led flash continuously and do you get a message at the top of the menu about genlock disabled?

EDIT:
anightin wrote:
Sat Jun 13, 2020 5:15 pm
In any case the 50Hz is now being selected and genlocking nicely.
So I guess the question now is, where are the ". xxxx" files coming from?
Yes, I just noticed those dots, that is not normal.
Do all the 50Hz non-dot ones work or only the test ones?

I think Macs have resource forks on files so mabe it is adding them as hidden files on the SD card.
Do you get similar dot files on the profiles as well?

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by anightin » Sat Jun 13, 2020 5:36 pm

IanB wrote:
Sat Jun 13, 2020 5:28 pm
anightin wrote:
Sat Jun 13, 2020 5:15 pm
Many thanks, I still get 1080p 60Hz output on both test files:
What scaler is this?
I assume you are trying to use it in passthrough mode

Does the genlock led flash continuously and do you get a message at the top of the menu about genlock disabled?
Now it’s working at 50Hz the genlock flashes for a couple of seconds then stays lit. No messages.
A1F0AACF-A37B-4E95-AFE1-283BD438602A.jpeg
28A4555C-03CE-4654-948E-C4AAECDBBEDE.jpeg
FDA0158F-9BCA-4A46-B57F-9242644BEE81.jpeg

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by anightin » Sat Jun 13, 2020 5:42 pm

IanB wrote:
Sat Jun 13, 2020 5:28 pm
I think Macs have resource forks on files so mabe it is adding them as hidden files on the SD card.
Do you get similar dot files on the profiles as well?
Yup, I blame my Mac, and will have to make a note to ignore all ". xxx" options :?

Yes they appear in multiple places incl. profiles

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by IanB » Sat Jun 13, 2020 5:46 pm

anightin wrote:
Sat Jun 13, 2020 5:42 pm
Yup, I blame my Mac, and will have to make a note to ignore all ". xxx" options :?
Yes they appear in multiple places incl. profiles
Yes it's a Mac resource fork:
https://discussions.apple.com/thread/4256797
Doesn't look like you can stop their creation so I'll tweak the next release to ignore all files beginning with ._ (underline gets converted to space for display in the menus)

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by anightin » Sat Jun 13, 2020 6:38 pm

IanB wrote:
Sat Jun 13, 2020 5:46 pm
anightin wrote:
Sat Jun 13, 2020 5:42 pm
Yup, I blame my Mac, and will have to make a note to ignore all ". xxx" options :?
Yes they appear in multiple places incl. profiles
Yes it's a Mac resource fork:
https://discussions.apple.com/thread/4256797
Doesn't look like you can stop their creation so I'll tweak the next release to ignore all files beginning with ._ (underline gets converted to space for display in the menus)
Thanks again for your help Ian =D>

BTW Got the analogue boards working now (well the first one anyway) with my trusty ZX81. Took a bit of tweaking on the sampling menu on DAC-A and DAC-F before I got a stable picture but looks great!

:D
IMG_7137.jpeg
IMG_7136.jpeg
IMG_7135.jpeg

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by IanB » Sat Jun 13, 2020 8:02 pm

anightin wrote:
Sat Jun 13, 2020 6:38 pm
BTW Got the analogue boards working now (well the first one anyway) with my trusty ZX81. Took a bit of tweaking on the sampling menu on DAC-A and DAC-F before I got a stable picture but looks great!
I'm using the direct ULA connection profile as I don't have a video interface on my ZX81 so the default values for those DACs on the standard ZX81 profile are likely not correct.
If you post your saved profile, I'll update it on the next release.
(Dont forget to run the Auto calibration again after finalising your DAC levels and then save the config again)

Here is an updated kernel file which hides all files beginning with '.'
kernelrpi.zip
(127.47 KiB) Downloaded 14 times
Let me know if it works OK for you.
(Need to check profiles, resolutions, palettes, and CPLDs)

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by danielj » Sat Jun 13, 2020 8:04 pm

IanB wrote:
Sat Jun 13, 2020 12:00 am
Another one to add to the supported list :)
You can make a specific profile by copying and renaming the existing Master 128 profile in /profiles/xxx but change the Auto Switch option to off.

Also if that image was meant to be centred, it looks like the H & V Offsets in the geometry menu could do with a little tweak.
(Best to use a full screen coloured background and centre up the rectangle)
Here you go :)

Big up to both you and hoglet for this one. I'd been meaning to build these for so long and I'm frankly blown away by the quality!

d.
Attachments
capture3.png
capture2.png
RML_480Z.txt
(104 Bytes) Downloaded 19 times

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by anightin » Sat Jun 13, 2020 8:35 pm

IanB wrote:
Sat Jun 13, 2020 8:02 pm

If you post your saved profile, I'll update it on the next release.
(Dont forget to run the Auto calibration again after finalising your DAC levels and then save the config again)
Sure, here is the saved profile for ZX81 with Composite Mod
ZX81_Comp_Mod.txt
(151 Bytes) Downloaded 19 times


Kernel mod seems to work fine too:

Before:
IMG_7138.jpeg
After:
IMG_7140.jpeg
:D =D>

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by anightin » Tue Jun 16, 2020 1:02 pm

Dear All,

Did a repeat for my ZX80 yesterday evening. It was in the queue for a composite mod too so did that all in one hit.
IMG_7159.jpeg
IMG_7160.jpeg
As expected the results were great!
IMG_7177.jpeg

I finished yesterday feeling very chuffed as now have all the RGB to HDMI boards + analogue boards I've made so far now working (BBC, Master, ZX81, ZX80)

However this morning my ZX80 developed a random reset issue. Not sure if it was my mod that upset it, or firing it up from a good few years slumber. I have ordered a high-efficiency regulator to replace the existing one and will try again.

I have posted on the ZX forum, but if anyone has seen this before and has any hints I'd appreciate it.

Best wishes

Andy

P.S: Here is my config file for the ZX80 above
ZX80_Comp_Mod.txt
(262 Bytes) Downloaded 15 times

Update:

New rectifier and caps seemed to solve the reset issue.
Last edited by anightin on Sat Jun 20, 2020 8:37 pm, edited 1 time in total.

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by IanB » Wed Jun 17, 2020 10:48 pm

I've ordered a small test batch of assembled RGBtoHDMI main boards from China so if that goes OK I will have some ready made ones available in due course.
I'll start a thread in the for sale forum once I have a better idea of the final price.

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by JohnJones » Thu Jun 18, 2020 12:18 am

IanB wrote:
Wed Jun 17, 2020 10:48 pm
I've ordered a small test batch of assembled RGBtoHDMI main boards from China so if that goes OK I will have some ready made ones available in due course.
I'll start a thread in the for sale forum once I have a better idea of the final price.
Excellent news. I'd certainly like to put my name down for one of the ready-made main boards.

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by anightin » Sat Jun 20, 2020 8:36 pm

Finally got round to digging out my Jupiter Ace for a recap, regulator update and composite mod.

My final RGB to HDMI adapter build was destined for this machine:
IMG_7222.jpeg
And testing with the composite mod was looking good:
IMG_7223.jpeg
I started off with my ZX81 profile for this machine (using the same composite converter) and all was going well, except I just can't seem to remove a vertical band of 'interference' that appears just past mid-screen at about 1/8th the width. It appears as shimmering pixels that roll from top to bottom. Playing around with the sampling menu seems to shift it left to right, wider or narrower but can't seem to make it go.

I wonder if this is actually something to do with the Jupiter Ace video circuit, itself, or the 6.5MHz crystal as touching it with my finger certainly has a marginal effect on the interference:
IMG_7226.jpeg

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by IanB » Sat Jun 20, 2020 8:45 pm

anightin wrote:
Sat Jun 20, 2020 8:36 pm
I started off with my ZX81 profile for this machine (using the same composite converter) and all was going well, except I just can't seem to remove a vertical band of 'interference' that appears just past mid-screen at about 1/8th the width. It appears as shimmering pixels that roll from top to bottom. Playing around with the sampling menu seems to shift it left to right, wider or narrower but can't seem to make it go.
Vertical bands of noise mean that the line length isn't set correctly so try adjusting that in the geometry menu (probably by +-1).
It will be set correctly when all pixels are clean or noisy after which, re run the calibration to get rid of any noise.

For further info see the tutorial on adding a new profile in the wiki:
https://github.com/hoglet67/RGBtoHDMI/w ... ew-Profile

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by anightin » Sat Jun 20, 2020 9:29 pm

IanB wrote:
Sat Jun 20, 2020 8:45 pm
anightin wrote:
Sat Jun 20, 2020 8:36 pm
I started off with my ZX81 profile for this machine (using the same composite converter) and all was going well, except I just can't seem to remove a vertical band of 'interference' that appears just past mid-screen at about 1/8th the width. It appears as shimmering pixels that roll from top to bottom. Playing around with the sampling menu seems to shift it left to right, wider or narrower but can't seem to make it go.
Vertical bands of noise mean that the line length isn't set correctly so try adjusting that in the geometry menu (probably by +-1).
It will be set correctly when all pixels are clean or noisy after which, re run the calibration to get rid of any noise.

For further info see the tutorial on adding a new profile in the wiki:
https://github.com/hoglet67/RGBtoHDMI/w ... ew-Profile
Spot on that fixed it Ian, many thanks -- Just needed nudging by +1 :D =D>
Jupiter_ACE_Composite.txt
(263 Bytes) Downloaded 23 times

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by hoglet » Sat Jun 20, 2020 10:34 pm

I don't know if this is any help:

Code: Select all

Jupiter ACE Dimensions and Timings
----------------------------------

The Z80 CPU is clocked at 3.25MHz. Picture size is 256x192 pixels.

Horizontal Timings
  Phase__________Dotclock_______________=_CPU Clock___________
  Hsync           32 pixels (320..351)  = 16 clks
  Left Border     64 pixels (352..415)  = 32 clks
  Picture        256 pixels (0..255)    = 128 clks
  Right Border    64 pixels (256..319)  = 32 clks
  Total          416 pixels (0..415)    = 208 clks

Vertical Timings
  Phase__________50_Hz_version__________60_Hz_Version_______
  Vsync            8 lines (248..255)     8 lines (224..231)
  Upper Border    56 lines (256..311)    32 lines (232..263)
  Picture        192 lines (0..191)     192 lines (0..191)
  Lower Border    56 lines (192..247)    32 lines (192..223)
  Total          312 lines (0..311)     264 lines (0..311)
Note: There are separate mainboards for 50Hz/60Hz (ie. the framerate isn't
software selectable).
From here:
https://problemkaputt.de/zxdocs.txt

The timings are consistent with this:
https://github.com/hoglet67/Ice40Jupite ... ogic.v#L67

Dave

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by IanB » Sat Jun 20, 2020 11:02 pm

anightin wrote:
Sat Jun 20, 2020 9:29 pm
Spot on that fixed it Ian, many thanks -- Just needed nudging by +1 :D =D>
From Hoglet's info the line length should probably be 416, not 415 (i.e 2 different from the ZX80).
It probably looks OK with 415 because the noise bar is on the extreme left or right of the screen in the black area so it isn't visible.

Also I think the ZX80/81 and Ace profiles should have 75R termination turned on as those adapters are designed to drive normal monitors which have 75R termination. It probably doesn't make much difference with the short cables we are using but it would be more technically correct so can you try changing the Input Coupling setting to "DC/75R Termination" in those profiles as well.
After doing that, the DAC-A and DAC-F thresholds will probably need to be adjusted and the best way to find the optimal value is to alter them in both directions until video stops working properly and then set them to half way between those values.

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by anightin » Sat Jun 20, 2020 11:11 pm

IanB wrote:
Sat Jun 20, 2020 11:02 pm
anightin wrote:
Sat Jun 20, 2020 9:29 pm
Spot on that fixed it Ian, many thanks -- Just needed nudging by +1 :D =D>
From Hoglet's info the line length should probably be 416, not 415 (i.e 2 different from the ZX80).
It probably looks OK with 415 because the noise bar is on the extreme left or right of the screen in the black area so it isn't visible.

Also I think the ZX80/81 and Ace profiles should have 75R termination turned on as those adapters are designed to drive normal monitors which have 75R termination. It probably doesn't make much difference with the short cables we are using but it would be more technically correct so can you try changing the Input Coupling setting to "DC/75R Termination" in those profiles as well.
After doing that, the DAC-A and DAC-F thresholds will probably need to be adjusted and the best way to find the optimal value is to alter them in both directions until video stops working properly and then set them to half way between those values.
Thanks Ian and Dave, if I get chance tomorrow I will tweak further and re-post the Jupiter profile :)

Update: New profiles for composite Jupiter Ace given 416 line length and 75R termination, and for composite ZX80/81 with 75R termination

Rock steady picture :)
Jupiter_ACE_Composite.txt
(262 Bytes) Downloaded 18 times
And the one for ZX80/81:
ZX80_Composite.txt
(261 Bytes) Downloaded 20 times
ZX81_Composite.txt
(261 Bytes) Downloaded 15 times
Last edited by anightin on Sun Jun 21, 2020 3:53 pm, edited 4 times in total.

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by biggestsonicfan » Sun Jun 21, 2020 3:39 am

IanB wrote:
Wed Jun 17, 2020 10:48 pm
I've ordered a small test batch of assembled RGBtoHDMI main boards from China so if that goes OK I will have some ready made ones available in due course.
I'll start a thread in the for sale forum once I have a better idea of the final price.
Sorry to pop in as a newbie, but I am also interested here in a prefab, but I am unsure what version I would need. Rather than a conventional old-school computer, I would be pairing one of these with the rather strange video output of a Sega Model2b arcade board. Specs can be found here. I'm currently using a GBS-8220 with GBSControl, but would love a custom solution for HDMI capture, better than a VGA2HDMI converter. I'm just not entirely sure this project is compatible with a more modern system like the Model2b, but I am intrigued and would like to give it a shot. If anyone savvy can confirm or deny whether this project would work based on specs, that would be the best starting point for me. Thanks in advance.

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by hoglet » Sun Jun 21, 2020 8:17 am

biggestsonicfan wrote:
Sun Jun 21, 2020 3:39 am
I'm just not entirely sure this project is compatible with a more modern system like the Model2b, but I am intrigued and would like to give it a shot. If anyone savvy can confirm or deny whether this project would work based on specs, that would be the best starting point for me. Thanks in advance.
> Color depth: 65,536 (16bpp), 16,777,216 (24bpp),[24] 256 (8bpp)

Unfortunately not; it has far to many colours.

RGBtoHDMI can only distingish ~3 (ish) different levels for each of RGB.

i.e. It's really designed for old-school 8-bit systems.

Dave

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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by biggestsonicfan » Sun Jun 21, 2020 4:25 pm

hoglet wrote:
Sun Jun 21, 2020 8:17 am
> Color depth: 65,536 (16bpp), 16,777,216 (24bpp),[24] 256 (8bpp)

Unfortunately not; it has far to many colours.

RGBtoHDMI can only distingish ~3 (ish) different levels for each of RGB.
No worries, thanks much for confirming for me. Good luck to everyone on this fantastic project! Glad to see retrocomputing living in an HDMI world! :D

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*STEVE
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Joined: Fri Jul 26, 2019 8:22 pm
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Re: RGB to HDMI using a Pi Zero and a small CPLD

Post by *STEVE » Mon Jun 22, 2020 2:12 am

So, I've built one up using parts I had available, the XC9572XL dev board in the original jumper-wired version and proto-board, but to the latest spec schematic (rgb-to-hdmi.shc and using the front-end from the three-bit-buffer (buffer.sch). I've programmed the CPLD sucessfully (to the newer 6-bit version since i've built wired this up to the 6-bit schematic) but am seeing two things when it boots. One, it's saying 'no sync detected' although there is on the SYNC line (buffered through the 74LS08) and the interface is stuck at '6 BIT RGB', although I think this should reflect 3-BIT TTL.

I suspect this is just a wiring error and the PI thinks I'm using the 6 bit analogue interface when I want to use the 3-Bit TTL.. Q1: how is the interface type detected?

I my 3-bit buffered RGB inputs go to RED, GREEN, BLUE and I've left BRED BGREEN, BBLUE not-connected. Q2: Are the 4K7 pull-down's necessary?

I appreciate this is a bit of a franken-version but trying to use this to check performance before investing in getting PCBs manufactured.

Steve.
  • BBC Model B+ 128k
  • BBC Master 128k
  • Econet (+L3 fileserver/Arduino Filestore)
  • BBC Buggy
  • Jessop-Ralph Turtle (WIP)
  • A3020 (WIP)
  • +more

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