Commodore 128 - 80 Columns w/OSSC

[Moe]

Hey everyone,

 

I just got a Commodore 128 last week, and I also ordered a OSSC about 2 weeks ago (I should receive it in a few weeks, I hope).

 

If I want to run my C128 in 80 column mode I need to use the RGBI output.  Can I connect the RBGI port, on the C128, directly to the VGA port on the OSSC?  Or do I need to use a CGA2RGB to convert the digital RBGI signal to analog, before feeding it into the OSSC's VGA port?  I have seen a few posts about doing this with a GBS-8200, but none using a OSSC.

 

Any information you might have will be greatly appreciated.  

 

 

Cheers,

Moe

 

[carlsson]

The RGBI uses TTL levels (nominally 5V, I believe). All documentation about the OSSC warns from connecting such signals directly, so you need a converter to make it analog RGB. I don't know about the CGA2RGB specifically, but if you are into soldering it is relatively easy to build a voltage divider per one of the SCART schematics online.

[Moe]

Thanks for the info!  The CGA2RGB can convert from RGBI to RGBs (https://gglabs.us/node/2063), and the OSSC can accept an RGBs signal.  I order a CGA2RGB to test with my C128 and OSSC. 

 

Once I receive the CGA2RGB I'll update this topic with my results.

 

 

Cheers,

Moe

 

[djc6]

On 6/30/2020 at 2:06 PM, Moe said:

Thanks for the info!  The CGA2RGB can convert from RGBI to RGBs (https://gglabs.us/node/2063), and the OSSC can accept an RGBs signal.  I order a CGA2RGB to test with my C128 and OSSC. 

 

Once I receive the CGA2RGB I'll update this topic with my results.

 

Moe, what was the final verdict?  I'm trying to attempt the same - CGA2RGBv2 / OSSC / C128 in 80-column mode.  

Any settings you had to tweak on the OSSC?  Thanks!

[Moe]

On 8/22/2020 at 11:31 AM, djc6 said:

Moe, what was the final verdict?  I'm trying to attempt the same - CGA2RGBv2 / OSSC / C128 in 80-column mode.  

Any settings you had to tweak on the OSSC?  Thanks!

Thanks for asking, it forced me to get back to it!

 

Yes, I was able to get 80 column mode working with the CGA2RGBv2 & OSSC.

 

CGA2RGBv2 

DIP1 to DIP4 = off

Jumper J4 - pin 2-3

I created a USB 5V power cable to power the CGA2RGBv2, since the OSSC does not provide the power.

 

OSSC

AV3 - RGBHV

 

 

Cheers,

Moe

[djc6]

I was able to dramatically improve the picture of the CGA2RGBv2 & OSSC combination by doing a deep dive into the OSSC settings with help from VGP forum:

 

https://videogameperfection.com/forums/topic/commodore-128-cga2rgbv2/

 

Attached are some photos - it looks a lot better in person, for example none of the color fringing in the GEOS128 photo is present in person.

 

Settings I am using:

240p / Line2x

H. samplerate 1016
H. synclen 20
H. backporch 241
H. active 640
V. synclen 3
V. backport 36
V. active 200
Sampling Phase 11 degrees

 

 

Edited September 8, 2020 by djc6