Reply To: New Koryuu test firmware 1.1-test0

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Hi Megari,

I’m using the Koryuu with a Capcom CPS changer S-video output with Street Fighter 2 Turbo PCB.

The connection is:
Capcom CPS changer S-video -> Koryuu -> Component Video -> RetroTink Comp2RGB -> PVM

With the stock Koryuu firmware, I encountered a strange issue where after 5 minutes of operation, the video starts to flicker and eventually it loses all color.

A direct S-video connection into my PVM display is ok. The S-video input to a RetroTink 2x Pro to an HDMI display is ok too.
I have separately tested the RetroTink Comp2RGB -> PVM connection with a SNES -> HD retrovision cable -> RetroTink Comp2RGB -> PVM, and verified that works fine. Thus, I believe there may be an issue with how the Koryuu is handling the S-video output of the CPS Changer.

I suspect there may be some issue with the field reversal and updated the Koryuu firmware to version 1.1 to see if the issue goes away. The updated firmware did seem to help the issue, but after several minutes of operation, I could see the video start to flicker again under certain scenarios/screens. It seems that the issue gets cleared out between screen transitions, but certain video input patterns seem to trigger the flickering/color issue. The start up screen/attract mode with vertical scrolling seems to be problematic, as is Chun Li’s stage for some reason. I think the field reversal solution helps, but it seems there remains some residual issue that is still not fully resolved. Do you have any theories why this might be happening?

A side note on the firmware update procedure, as it took me a while to get this working with proper driver and programmer software:
1. I used the Olimex AVR-ISP-MK2 ( with AVR-ICSP 10-to-6 cable (
2. I have a Mac with Windows 7 via Parallels
3. I had to manually install drivers as recommended by Olimex (,
4. I was not able to get Khazama AVR programmer ( to work. Instead I was able to use Atmel Studio 7 ( to flash the Koryuu.