To easily connect a CPC to a VGA cable I'd love to have an adapter PCB which is much easier and more reliable to solder than an adapter cable. I made a quick design for a PCB but I am not sure if it should contain resistors or not.
For the Atari ST, it also works without anything but it's reported, that with resistors in the RGB lines (45-100 Ohms are mentioned) the quality will be (much) better. Also someone discovered that some capacitors for hsync and vsync (10nF and 470pF) can help with the quality.
Will those resistors be a benefit on the CPC too? And would a capacitor for Csync also improve the quality?
(https://www.cpcwiki.eu/imgs/thumb/6/65/CPCVGAconnectorPinouts.png/800px-CPCVGAconnectorPinouts.png)
For real VGA you must add separator Hsync and Vsync (PIN14)
Csync work only with VGA-RGB-IN. like TV or 15kHz Monitor.
Quote from: McArti0 on 16:30, 03 December 23For real VGA you must add separator Hsync and Vsync (PIN14)
I couldn't find the original spec but according to some sources (e.g. https://en.wikipedia.org/wiki/VGA_connector) pin 13 accepts both H-sync and C-sync. It might be that some VGA monitors behave differently but I have never come across one. I own an adapter which splits C-Sync into H-Sync and V-sync but I never had a situation where this adapter works but a pure 1:1 connection from C-Sync to pin 13 doesn't.
I have BW analog VGA monitor H35kHz. And I must add Lm1881 separator to use it.
That's the problem with VGA monitors. What works on one, doesn't necessarily work on another. If you are going to make a really good CPC to VGA adapter, you should make it extremely flexible. Switchable variable resistors on the colour signal and the choice to split or combine the sync signals.
Bryce.
I'd like to try the simple one because I'd like to use it with a VGA to HDMI converter.
If it works, it would make me very happy :D
As I don't know how to apply a sync splitter to it, it probably will be not a very good adapter, but maybe a good enough adapter for most cases.
I just ordered some PCBs for another project where I use the same VGA connector footprint. Once they are here I can check that the footprint fits. If that's the case, I will order the CPC2VGA PCBs and give it a try. If everything works, I will publish it. As I will have plenty of PCBs I can also send them to whoever is interested and is willing to pay for postage (worldwide 2€, Germany 1€, all untracked).
Quote from: eto on 21:04, 03 December 23As I don't know how to apply a sync splitter to it, it probably will be not a very good adapter, but maybe a good enough adapter for most cases.
Do a search for LM1881. That chip does all the splitting for you. :)
Bryce.
Quote from: Bryce on 09:21, 04 December 23Do a search for LM1881. That chip does all the splitting for you. :)
I did. But it seems it needs some additional resistors and capacitors and I am not sure if I can just copy/paste the schematics.
Regarding power supply: A few years ago I bough an adapter from Spain which doesn't use the LM1881 and requires no power. From the components it looks very similar to a 74LS123 based splitter. I don't know for sure as the number is removed from the IC.
Is it possible that this gets the power from the LUM signal like the Scart hack does? If yes, could that also work for the LM1881 or LM1980?
For a proper implementation it also needs a nand and an and gate as well.
See here:
https://www.epanorama.net/documents/vga2rgb/vgamonitor.html
In the section of "How can I build a circuit which converts composite sync signal to HSYNC and VSYNC ?"
There is the full layout. The problem is, that the LM1881 does not ouput HSYNC, but just VSYNC and passes a Composite Sync (so the composite signale without the actual video signal).
It might work, but it also might not.
The proper implementation would be with the two gates to ensure, that you get proper HSYNC signal.
Quote from: eto on 10:46, 04 December 23Quote from: Bryce on 09:21, 04 December 23Do a search for LM1881. That chip does all the splitting for you. :)
I did. But it seems it needs some additional resistors and capacitors and I am not sure if I can just copy/paste the schematics.
Regarding power supply: A few years ago I bough an adapter from Spain which doesn't use the LM1881 and requires no power. From the components it looks very similar to a 74LS123 based splitter. I don't know for sure as the number is removed from the IC.
Is it possible that this gets the power from the LUM signal like the Scart hack does? If yes, could that also work for the LM1881 or LM1980?
I have this too hehe.
@eto it looks like he uses a proper implementation with this chip EL4583, which is a better solution to the problem, as it directly outputs VSync and HSync and you only need some resistors and capacitors:
Where do you get the information that it uses a 74LS123 ?
https://www.digikey.de/de/products/detail/rochester-electronics-llc/EL4583AIS-T7/11523794
https://rocelec.widen.net/view/pdf/598jp2pzwr/INSL-S-A0001389934-1.pdf?t.download=true&u=5oefqw
And here is a link to another picture, where you can read half of the chip marking.
Does not look like a 74LSxxx chip.
Quote from: SerErris on 11:40, 04 December 23Where do you get the information that it uses a 74LS123 ?
It was a guess based on this circuit which contains very similar elements: https://www.electroschematics.com/sync-signal-separator/
Quote from: SerErris on 11:33, 04 December 23The problem is, that the LM1881 does not ouput HSYNC, but just VSYNC and passes a Composite Sync (so the composite signale without the actual video signal).
I read that this is not a problem if the H-Sync is fed with C-Sync.
Quote from: SerErris on 11:40, 04 December 23t looks like he uses a proper implementation with this chip EL4583
The EL4583 is fed with Composite video which the CPC does not have. It has only Composite Sync. LUM is "kind of" a composite video signal.
I think I will check the adapter and see how the pins are connected. That might give an idea. Also how it gets power.
Typically with VGA, there are really all kind of monitors. Some of them do accept CSync at HSync, Some of them do not accept CSync at HSync at all and some do not if VSync is available (HSync cannot be CSync).
Regarding Composite Video - That is true for both LM1881 and EL4583.
Quote from: eto on 12:23, 04 December 23I think I will check the adapter and see how the pins are connected. That might give an idea. Also how it gets power.
I have absolutely no clue what that thing is doing. CSync of the CPC is directly connected to pin 13 of the VGA connector. CSync also goes to a pin of the IC but it's neither the pin it should be for the EL4583 nor the LS123. I also do not understand where it could get the power from.
Pin 9 of the VGA connector is connected to some if the passive components which doesn't make any sense at all as this should be a 5V signal to the monitor.
Unfortunately I can't test any of the pins on one side of the IC as they are covered by the VGA connector.
It is definetely not an 74LS chip. That marking would be clear do read and longer then the red X in the picture above.
You could pair it with a 74XX00 Chip (4-Nand) to implement the clean H-Sync.
However the diagram posted here https://www.electroschematics.com/sync-signal-separator/ (https://www.electroschematics.com/sync-signal-separator/) must be faulty.
It connects with a R/C timing network the VCC line with CExt but that is supposed to get placed between RCExt and CExt. In the first vibrator that is correct, in the second it is wrong (to my understanding) RCExt is floating, which would result in unpretictable behaviour. (Pin7 and Pin6 should be connected, not Pin16 and Pin6).
There is another chip (10 pins only) LMH1980,
https://community.lzxindustries.net/t/sync-extraction-circuit/3496/5
That looks like a very simple setup, because you can ignore all the input stuff from CSync IN (e.g BNC buffer and stuff) as we do not have a high frequency signal and it is also only a Sync signal without any video data in it.
This chip is VSSOP, so pretty small on the PCB and requires minmal other components. It actually requires 1 Resistor to pull Rext down and on decoupling capacitor (they put in two in the schematics) 10uF and 0.1uF.
Not sure about the output Resistors, maybe you want to put them in, but I thing they are there to get a 100Ohm output resistance as defined resitance.
https://www.ti.com/lit/ds/symlink/lmh1980.pdf?ts=1701767569476&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252Fde-de%252FLMH1980
BTW: I still do not understand where the Power Supply is coming from.
What Chip code do you read on the X-Picture above?
Ist it:
?
I could not find anything on that chip.
Here is a quick setup with the LMH1980, that should actually work and is very little efford. I am not sure about the 75Ohm resistors to be honest. The specification VGA mentions them in the signal path, but not for the logic ... so this could be either logic or signal - not sure.
So if they are not required, you can simply bridge them.
Quote from: SerErris on 10:38, 05 December 23What Chip code do you read on the X-Picture above?
Ist it:
?
I could not find anything on that chip.
Those are manufacturing dates and locations. Not the Chip part number.
Bryce.
Quote from: SerErris on 10:30, 05 December 23BTW: I still do not understand where the Power Supply is coming from.
At the moment I guess it comes from pin 9 of the VGA connector. I read somewhere that pin 9 sometimes carries 5V. Not sure if that's really the case.
That finally could also explain why my NEC 1970 works with the ST but not with the CPC. I checked its schematics of the NEC and it expects V-sync and H-sync on separate pins and pin 9 does not supply 5V. Then the Aranet adapter would just be a pure passive adapter which only provides C-sync to pin 13 and the NEC will not receive the right signal.
For a community solution I personally would prefer to use components that are easily available. I can't find a source to buy the LMH1980 in small quantities. The LM1881 however is easily available. I think it might even be able to use through-hole components so the whole adapter still fits perfectly behind the CPC.
Pin 9 might be connected on the monitor side in some monitors, but it not standard and relatively rare. If that's the source, then the adapter will only work on a few carefully chosen monitors. It has to get power from somewhere though. The CPC LUM can be used (with a capacitor) to build up a voltage, but that could never supply enough current to power even a very low power 5V IC.
Thru-hole LM1881 are still easy to find.
Bryce.
Thruhole is to large for this connector.
Here you can buy it in small and large quantities:
https://www.digikey.de/de/products/base-product/texas-instruments/296/LMH1980/62143
Quote from: SerErris on 19:33, 05 December 23Here you can buy it in small and large quantities:
in theory yes, in practice it's 18€ for shipping which makes it no longer feasible.
Quote from: SerErris on 19:33, 05 December 23Thruhole is to large for this connector.
I found a very simple circuit which has been reported to work in a similar context. If that works for the CPC, it should fit onto a PCB. Even including a 5.5/2.1mm connector. The 5V from the power supply go into the adapter and from there a short power cable into the CPC.
Quote from: eto on 15:36, 06 December 23Quote from: SerErris on 19:33, 05 December 23Here you can buy it in small and large quantities:
in theory yes, in practice it's 18€ for shipping which makes it no longer feasible.
Quote from: SerErris on 19:33, 05 December 23Thruhole is to large for this connector.
I found a very simple circuit which has been reported to work in a similar context. If that works for the CPC, it should fit onto a PCB. Even including a 5.5/2.1mm connector. The 5V from the power supply go into the adapter and from there a short power cable into the CPC.
That's a great usage of PCB real estate. By putting the VGA and CPC connector on the bottom side you've seriously shrunk the size of the board. Going SMD would shrink it further, but that takes away from the Retro look, so I wouldn't go that far.
Bryce.
I tried this setup but it didn't work with my 15khz monitor (BENQ BL912)
I double checked my makeshift cable with a multimeter but it was all good.
I don't know if it's the Csync problem or not.
Acording to source on the net, it requires HSync and Vsync, where HSync can be just forwarded CSync, but VSync is something you need to derive from CSync.
Quote from: eto on 15:36, 06 December 23Quote from: SerErris on 19:33, 05 December 23Here you can buy it in small and large quantities:
in theory yes, in practice it's 18€ for shipping which makes it no longer feasible.
Quote from: SerErris on 19:33, 05 December 23Thruhole is to large for this connector.
I found a very simple circuit which has been reported to work in a similar context. If that works for the CPC, it should fit onto a PCB. Even including a 5.5/2.1mm connector. The 5V from the power supply go into the adapter and from there a short power cable into the CPC.
Looking at the picture I think you are missing a decoupling cap on the 1881 ... It is general good practice to decouple any IC to ensure stable operation.
Another idea is that you can put a male barrel power connector to the CPC on the same board next to the 6-pin DIN connector. So you plug in both and plug in power from the monitor into the I am not sure if a vertical barrel connector exists to solder on - but that would be great. However you would need different adapters for 464 and 6128 then. On first glance, those were not in the same position.
Quote from: SerErris on 19:22, 11 December 23Looking at the picture I think you are missing a decoupling cap on the 1881 ... It is general good practice to decouple any IC to ensure stable operation.
You mean between VCC and GND? true... I forgot that.
Quote from: SerErris on 19:22, 11 December 23Another idea is that you can put a male barrel power connector to the CPC on the same board next to the 6-pin DIN connector. So you plug in both and plug in power from the monitor into the I am not sure if a vertical barrel connector exists to solder on - but that would be great. However you would need different adapters for 464 and 6128 then. On first glance, those were not in the same position.
That was my first idea when I looked at the back of the 6128 and the 464. But I could not find a vertical barrel connector that could be soldered on the PCB. For now, my idea is to have the 5V and GND on the PCB so you can solder a short cable with a barrel plug. The 5V from the power supply will go into the female barrel connector on the PCB (top right corner) and from the 5V/GND on the PCB the connection will then go into the CPC. I probably need bigger traces but there should be enough space on the PCB to make that work.
Maybe something like this, but most likely the plastic part is to long:
(https://upload.wikimedia.org/wikipedia/commons/thumb/6/68/Photo-RoundPowerConnectors.jpg/525px-Photo-RoundPowerConnectors.jpg)
Quote from: SerErris on 22:17, 11 December 23Maybe something like this, but most likely the plastic part is to long:
definitely too long.
I have just ordered two LM1881 and will test the set-up in a breadboard as soon as possible (but might be after Christmas).
will definitely work
CRT Philips 109s has VESA standard and read Csync from Amstrad.
ps. this is Mode 1, 160x200. possible 200x480. CRT recognize min. 28.5kHz from Amstrad.
Hi eto! Cool project! Such an adaptor is a great idea. Saving space and providing more stability compared to some self-soldered cable. :) :) :)
Quote from: GUNHED on 15:00, 13 December 23Such an adaptor is a great idea.
I'm not the one who had the idea in the first place. It's just that existing adapters are flawed and either expensive or unavailable. Let's hope it works and then I can add it to the Wiki.
I finally had time to test it - and it was successful. With a LM1881 the NEC now outputs the CPCs display signal.
I will now order the PCBs and test them next.
Does this work well with games that use CRTC tricks for smooth scrolling?
(Like Ghosts n Goblins)
Quote from: ervin on 06:04, 29 January 24Does this work well with games that use CRTC tricks for smooth scrolling?
(Like Ghosts n Goblins)
The adapter does not do anything to the signal (except for splitting it), it totally depends on the monitor (or converter/scan doubler) what works and what is unplayable.
I did some tests in the past and the screens I had that accept the CPC signal directly also worked well with most (!) games including Ghosts'n Goblins. But e.g. Relentless didn't work on a single configuration. What I found interesting: Super Edge Grinder was unplayable but Edge Grinder was perfectly smooth.
It's a different story with scan doublers or HDMI converters. Many of them have issues with Ghost's n Goblins. That can also be the case for TVs with RGB input as some seem also to have a RGB2HDMI converter built-in, which are bad for screen lag and can have issues with CRTC tricks.
I'll do some tests with the NEC monitor as I could not test it in the past and at least on the Amiga and Atari ST the NEC seems to be one of the best 15kHz compatible TFTs.
The PCBs finally arrived - and of course I made some minor and one major mistake ;-) (I switched 5V and GND... argl)
Anyway - it was good enough to see that it works and to hopefully make the final version of the circuit. Btw: The 75Ohm resistors in the RGB lines might not be necessary. In that case, they can just be bridged. I'll keep them in the PCB as it's easy to bridge them if not needed and much harder to add if required.
A SMD version would not save much space as the connectors will still stay huge and need some space next to each other with the empty space just being enough for through-hole components.
The circuit is a 1:1 copy of the original circuit in the LM1881 datasheet, no changes needed to be applied.
I'd love to know how that works with a VGA to HDMI converter, as it would make my CPC life easier.
Is it easy to get the power cable splitter or do we have to build it ourselves?
Other than that, looking good! (aka I'd like to try it ;D )
Quote from: robcfg on 22:45, 11 February 24I'd love to know how that works with a VGA to HDMI converter, as it would make my CPC life easier.
Is it easy to get the power cable splitter or do we have to build it ourselves?
Other than that, looking good! (aka I'd like to try it ;D )
Most likely it wouldn't work at all. It's extremely unlikely that any of those converters recognise anything below 31.469kHz.
Bryce.
Quote from: robcfg on 22:45, 11 February 24Is it easy to get the power cable splitter or do we have to build it ourselves?
You can get "DC splitter cables" for a few bucks on Amazon.
It's also possible to get the power from this PCB. There are pads to pass through the power from the jack. You can solder two wires to those pads and attach a power connector. This power connector goes into the CPC and the 5V cable from the monitor goes into the power jack on the PCB.
Btw: I'm already thinking about a solution that plugs into the CPC including a power connector. But that will also require a 3d printed case... not sure if it's robust enough.
Quote from: eto on 09:19, 29 January 24What I found interesting: Super Edge Grinder was unplayable but Edge Grinder was perfectly smooth.
SEG has an addition in comparison to EG. At the end of the stage, the scrolling stops to host the boss fight. Perhaps this is what results in the drastic difference you are getting, but I am not sure. Perhaps
@Axelay could shed some light?
Quote from: rexbeng on 11:47, 12 February 24Quote from: eto on 09:19, 29 January 24What I found interesting: Super Edge Grinder was unplayable but Edge Grinder was perfectly smooth.
SEG has an addition in comparison to EG. At the end of the stage, the scrolling stops to host the boss fight. Perhaps this is what results in the drastic difference you are getting, but I am not sure. Perhaps @Axelay could shed some light?
Sorry, no idea. It was quite a while ago now, but I thought the split code was unchanged between them so I'm not sure why they'd be behaving differently.
I have the CPC2VGA adapter from Edu Arana. Works really well with a Microvitech multiscan CRT monitor. I would happily get one of these
@eto if it includes a 3D printed case. I love Edu's adapter but all those exposed PCB freak me out a bit. BTW,
@eto, if you want me to check anything on the adapter I have or I can help somehow, give me a shout.
Quote from: nikos_a on 15:40, 01 March 24I have the CPC2VGA adapter from Edu Arana.
Wow! Thanks to you I googled and discovered their store. What a great selection of hardware!!
I've been seeking CSync2HVSync – Sync converter for a while, with no luck.
Cheers
Quote from: dodogildo on 16:54, 01 March 24Wow! Thanks to you I googled and discovered their store. What a great selection of hardware!!
I've been seeking CSync2HVSync – Sync converter for a while, with no luck.
Cheers
The one from Arananet seems to require that the monitor provides the power. If there is no power coming from the monitor (which e.g. the NEC 1970NXp does not do), the adapter will not split the sync signal.
Quote from: eto on 08:45, 02 March 24The one from Arananet seems to require that the monitor provides the power. If there is no power coming from the monitor (which e.g. the NEC 1970NXp does not do), the adapter will not split the sync signal.
My BENQ 912 is listed as having "full support" for "unpowered adapters" on this list, as opposed to NEC 1970NXp:
http://15khz.wikidot.com/
I hope Arananet adapter will work, if not I'll keep using my RGBtoHDMI or OSSC as always.
The BenQ accepts composite sync. Then any passive adapter will work too.
Quote from: eto on 08:45, 02 March 24Quote from: dodogildo on 16:54, 01 March 24Wow! Thanks to you I googled and discovered their store. What a great selection of hardware!!
I've been seeking CSync2HVSync – Sync converter for a while, with no luck.
Cheers
The one from Arananet seems to require that the monitor provides the power. If there is no power coming from the monitor (which e.g. the NEC 1970NXp does not do), the adapter will not split the sync signal.
In that case, what will be the output (if any)? I tried a Microvitec CRT and it worked fine. Then I also tried to connect the CPC to a Commodore 1940 and the image was not stable as seen in the video.
Quote from: nikos_a on 16:52, 04 March 24In that case, what will be the output (if any)? I tried a Microvitec CRT and it worked fine. Then I also tried to connect the CPC to a Commodore 1940 and the image was not stable as seen in the video.
The CPCs' sync signal is a composite sync signal and the Arananet adapter circuit is done in a way that it always routes the CPCs sync to H-sync, even if the IC is not powered. If the monitor accepts composite sync on H-Sync (which many VGA monitors do) then the adapter just acts like a simple passive adapter. That's as good as soldering a monitor connector to a VGA cable like this:
(https://www.cpcwiki.eu/imgs/6/65/CPCVGAconnectorPinouts.png)
(https://www.cpcwiki.eu/imgs/a/a2/ModernLCD_CPC2VGA2.JPG)
I own the Arananet adapter myself and it e.g. doesn't work with the Nec 1970NXp, as it doesn't accept composite sync.
I received my Arananet adapter today and I can now confirm that it works wonderfully.
(https://i.ibb.co/Jvkc2Gn/IMG-0970.jpg) (https://ibb.co/rxyQMzk)
(https://i.ibb.co/7GLtwmh/IMG-0967.jpg) (https://ibb.co/Hr3TW8Z)
Hi folks
I've got a short question, after I've researched eBay and Co...is there a way, to buy this adapter or PCB anywhere?
Best regards from Germany
ForD68
Quote from: ford68 on 09:48, 09 May 24I've got a short question, after I've researched eBay and Co...is there a way, to buy this adapter or PCB anywhere?
https://www.arananet.net/pedidos/product-category/cpc
Many thx for this quick reply...
...I've just placed an order.
Best regards
ForD68