Reply To: New Koryuu test firmware 1.1-test0

[megari]

Hi supermarkio,

Sorry for taking a few days to respond.

I have gone through my old data on CXA1645 and other chips used on the Sega Genesis Model 2 (as it is the closest match to this case), and based on my old oscilloscope captures, it seems that the color burst amplitude tends to sometimes be low on these units, especially so for CVBS output (sometimes barely 0.1 Vpp). S-Video output is usually fine. RGB output is basically always fine. The low amplitude for CVBS output is puzzling, as the specifications for the CXA1645, for instance, state that during normal operation, the output color burst amplitude is always in the range of 0.2 – 0.3 Vpp, 0.25 Vpp being typical.

I will probably have to obtain a few samples of representative hardware using this type of chip to properly investigate this. I’m hoping to be able to find someone relatively local who could lend me a Sega Genesis 2. A Capcom CPS changer would probably be even rarer in Europe.

That said, we can try and troubleshoot this a bit more. I have an experimental firmware image I would like you to test, if you do not mind. Please download it here. There are a few variants in the ZIP file, but unless you are willing to use the on-board USART serial port for logging debug output from the Koryuu, you’ll probably want to use the default or default_ntp variant.

The experimental firmware has one major change: the OPTION button no longer toggles smoothing, rather than cycles through different settings for the color kill threshold. On the first press, the Koryuu uses the most lenient threshold, where it only reverts back to grayscale if the color signal is very, very weak. Subsequent presses increase the threshold step by step, requiring ever higher color signal strength for color to be displayed. After the highest threshold setting, the threshold cycles back to the lowest setting.

The goal is to try finding out 1) Whether the issue happens even with the lowest threshold (first press of the OPTION button after power cycling the Koryuu), 2) If it does not, how many presses after the first one are required for the issue to occur.

Would you be willing to spare some of your time to try this experiment while I try to figure out the next step?

Thank you,
megari