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By msxmakers

Champion (468)

msxmakers's picture

23-07-2022, 12:10

RayneX wrote:

Would you be familiar with Capsule5000's O4Mega V2 RAM expansion board?

Capsule5000 is an MSXmakers member. Did you only find us by github? Do you never saw our Web/Blog?

Do you have all what you should need at:
https://msxmakers.design.blog/proyectos/o4mega/o4mega-v2-paso-a-paso/

By RayneX

Resident (43)

RayneX's picture

23-07-2022, 14:34

msxmakers wrote:
RayneX wrote:

Would you be familiar with Capsule5000's O4Mega V2 RAM expansion board?

Capsule5000 is an MSXmakers member. Did you only find us by github? Do you never saw our Web/Blog?

Do you have all what you should need at:
https://msxmakers.design.blog/proyectos/o4mega/o4mega-v2-paso-a-paso/

That's crazy. I am completely blind. I only found the github and it doesn't link back to the blog; only to Kiselev's github. I've definitely been to the blog cause that's where I got all the Step by step instructions for the Omega build and other "extensions" info like the DC12. I just didn't pay enough attention to the Projects Page to recognize it was there. SMH. Thank you again. I have all the BOM for the FMPAC and now O4Mega V2. That DC12 is really going to be convenient now. :)

By RayneX

Resident (43)

RayneX's picture

24-07-2022, 21:02

Just wanted to point out an FMPAC V2 discrepancy. https://msxmakers.design.blog/proyectos/f4-fmpac/f4-fmpac-v2...
I was trying to separate all the resistors for the BOM but Step 12 shows R4's value to be 4.7K, but the BOM List shows R4 to be 1K. From the PCB, it looks like 1K. Pointing this out because people may order the wrong Qty if they don't have the resistors on hand.
Also Step 17 is between Step 11 and 12.

By msxmakers

Champion (468)

msxmakers's picture

04-08-2022, 12:56

RayneX wrote:

Just wanted to point out an FMPAC V2 discrepancy. https://msxmakers.design.blog/proyectos/f4-fmpac/f4-fmpac-v2...
I was trying to separate all the resistors for the BOM but Step 12 shows R4's value to be 4.7K, but the BOM List shows R4 to be 1K. From the PCB, it looks like 1K. Pointing this out because people may order the wrong Qty if they don't have the resistors on hand.
Also Step 17 is between Step 11 and 12.

Thank you, now is fixed.

By RayneX

Resident (43)

RayneX's picture

05-08-2022, 21:43

Can anyone help with describing what the AV and Ys pins actually do in the RGB port of the Omega? I'm trying to make a Cable adapter that will work with HD Retrovision cables as it adapts to RGB ports very nicely in many instances. The RGB, Audio, Ground, and Composite are well known and described, but I also need a 5v source for the HDRV cables and I'd imagine the same with SCART? (I'm clueless on SCART standards). I see the AV line pump 4.55v, but not sure if that's sufficient. And I have no clue if Ys would actually be used. When researching the GBS control add on, both the AV and Ys pins aren't used, so it makes me wonder what they could be for. Any help with this would be appreciated. It'll be good info for us in the US that can adapt the port to use Component connections that is common here. Thanks in advance.

By msxmakers

Champion (468)

msxmakers's picture

06-08-2022, 00:04

RayneX wrote:

Can anyone help with describing what the AV and Ys pins actually do in the RGB port of the Omega? I'm trying to make a Cable adapter that will work with HD Retrovision cables as it adapts to RGB ports very nicely in many instances. The RGB, Audio, Ground, and Composite are well known and described, but I also need a 5v source for the HDRV cables and I'd imagine the same with SCART? (I'm clueless on SCART standards). I see the AV line pump 4.55v, but not sure if that's sufficient. And I have no clue if Ys would actually be used. When researching the GBS control add on, both the AV and Ys pins aren't used, so it makes me wonder what they could be for. Any help with this would be appreciated. It'll be good info for us in the US that can adapt the port to use Component connections that is common here. Thanks in advance.

I think they are both something mentioned as carrier voltage, a voltage reference signal without power enough. It could be also maybe anything called BURST.
Follow the Omega's schematic and you will see just a voltage divider.
Regards.

By RayneX

Resident (43)

RayneX's picture

06-08-2022, 00:13

msxmakers wrote:
RayneX wrote:

Can anyone help with describing what the AV and Ys pins actually do in the RGB port of the Omega? I'm trying to make a Cable adapter that will work with HD Retrovision cables as it adapts to RGB ports very nicely in many instances. The RGB, Audio, Ground, and Composite are well known and described, but I also need a 5v source for the HDRV cables and I'd imagine the same with SCART? (I'm clueless on SCART standards). I see the AV line pump 4.55v, but not sure if that's sufficient. And I have no clue if Ys would actually be used. When researching the GBS control add on, both the AV and Ys pins aren't used, so it makes me wonder what they could be for. Any help with this would be appreciated. It'll be good info for us in the US that can adapt the port to use Component connections that is common here. Thanks in advance.

I think they are both something mentioned as carrier voltage, a voltage reference signal without power enough. It could be also maybe anything called BURST.
Follow the Omega's schematic and you will see just a voltage divider.
Regards.

Yes, I read through the schematic and a friend told me it was just a voltage divider. It doesn't seem to be relevant to anything with the operation of the MSX Omega in any way though, right? My friend suggested removing the 10k resistor and then replace the 1k resistor with something like 120ohm on the AV line and that would give me all the signals I would need for HDRV as far as I know (keeping Ys disconnected as it's not used as far as I know). Just wanted to see if those two voltage divider lines actually did anything before I basically disable them to pull a good 5v source for the HDRV cable.

By ahmsx

Supporter (12)

ahmsx's picture

06-08-2022, 11:36

Hi,

The pinout of the Omega RGB connector is compatible with the Panasonic-style RGB cable and is documented at RGB (8-pin DIN 45326) wiki page.

The DIN signals are supposedly prepared to be wired directly to a SCART connector, so AV will end up in SCART pin 8 (which tells the monitor/TV that there is a signal on this input and can tell too the aspect ratio) and YS to SCART pin 16 (which tells the TV if the signal is RGB or composite).

The impedance of SCART pin 16 should be 75 ohm (which supposedly means that there is a Rx=75 ohm resistor connected to GND on the TV side). So if we have R36=120 ohm (the resistor near VCC=+5V) and R35=180 ohm (the resistor near GND) we have a voltage divider with an equivalent resistor near GND of RT=1 / (1/R35 + 1/Rx) = 1 / (1/180 + 1/75) = 52.9 ohm, which yields Vo Pin 16 = (VCC * RT) / (R36 + RT) = (5 * 52.9) / (120 + 52.9) = 1.53V, which will indicate a RGB video signal (1-3V).

On the other hand, the impedance of SCART pin 8 should be >10 Kohm (which supposedly means that there is a Rx=>10000 ohm resistor connected to GND on the TV side). Making a similar calculation (R33=1k near VCC, R14=10k near GND) we should have Vo Pin 8 >= 4.16V, which would land between the no signal (0-2V) and Widescreen 16:9 mode (4.5-7V) and out of 4:3 mode (9.5-12V). So if my calculations are right we have here an undefined behaviour, but it looks like it works (either because we manually select the source or because TV auto-selects out of specs).

Anyway, if you are not going to use a DIN to SCART cable, you can tweak those signals to your needs (just make sure you never connect a SCART cable if they get out of specs).

Cheers.

By msxmakers

Champion (468)

msxmakers's picture

07-08-2022, 13:02

RayneX wrote:

Yes, I read through the schematic and a friend told me it was just a voltage divider. It doesn't seem to be relevant to anything with the operation of the MSX Omega in any way though, right? My friend suggested removing the 10k resistor and then replace the 1k resistor with something like 120ohm on the AV line and that would give me all the signals I would need for HDRV as far as I know (keeping Ys disconnected as it's not used as far as I know). Just wanted to see if those two voltage divider lines actually did anything before I basically disable them to pull a good 5v source for the HDRV cable.

Hi, if you need 5v do not take it from a resistor divider because adding the resistor of your device connected to it the voltage will not be 5v anyway.

If you need 5v my suggestion will be you take it from the power source.

If you are going to modify the DIN-8 pin functions just make sure you will never connect a SCART or you will damange your TV.

By RayneX

Resident (43)

RayneX's picture

07-08-2022, 15:04

ahmsx wrote:

Hi,

The pinout of the Omega RGB connector is compatible with the Panasonic-style RGB cable and is documented at RGB (8-pin DIN 45326) wiki page.

The DIN signals are supposedly prepared to be wired directly to a SCART connector, so AV will end up in SCART pin 8 (which tells the monitor/TV that there is a signal on this input and can tell too the aspect ratio) and YS to SCART pin 16 (which tells the TV if the signal is RGB or composite).

The impedance of SCART pin 16 should be 75 ohm (which supposedly means that there is a Rx=75 ohm resistor connected to GND on the TV side). So if we have R36=120 ohm (the resistor near VCC=+5V) and R35=180 ohm (the resistor near GND) we have a voltage divider with an equivalent resistor near GND of RT=1 / (1/R35 + 1/Rx) = 1 / (1/180 + 1/75) = 52.9 ohm, which yields Vo Pin 16 = (VCC * RT) / (R36 + RT) = (5 * 52.9) / (120 + 52.9) = 1.53V, which will indicate a RGB video signal (1-3V).

On the other hand, the impedance of SCART pin 8 should be >10 Kohm (which supposedly means that there is a Rx=>10000 ohm resistor connected to GND on the TV side). Making a similar calculation (R33=1k near VCC, R14=10k near GND) we should have Vo Pin 8 >= 4.16V, which would land between the no signal (0-2V) and Widescreen 16:9 mode (4.5-7V) and out of 4:3 mode (9.5-12V). So if my calculations are right we have here an undefined behaviour, but it looks like it works (either because we manually select the source or because TV auto-selects out of specs).

Anyway, if you are not going to use a DIN to SCART cable, you can tweak those signals to your needs (just make sure you never connect a SCART cable if they get out of specs).

Cheers.

Thanks for the info. That's very insightful. SCART isn't a primary standard in the US so it'll never be an issue to avoid using it. And I did figure out what had to be done to make the HDRV cables work. It turned out to be the resistors that msxmakers mentioned. The 120 ohm resistor that I replaced with was still enough to impede the voltage and affect the HDRV from working properly even though I got 4.97v reading from it. We weren't expecting that. I'll post photos of the testing environment for it and the cable I had to make to use the 8 pin DIN to HDRV. I have a lot of updating to do. lol.

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