I finally managed to figure out why the Snood TAS I was puzzled by crashes on console. On this frame, the same frame that crashes on console, the game turns off DMA 2 after a audio FIFO reload is triggered but before it starts (there is a few cycles in between the two events.) I'm not entirely sure of the details yet, but this evidently triggers a crash. Presumably this is what GBA Tek refers to as: "DMA lockup when stopping while starting ???"
I'm not entirely sure yet how I will handle this in emulator, the behavior observed on console seems very complicated. I'll probably just trigger a jam state for now.
I'll put together a test to demonstrate the crash.
I successfully managed to setup an lm1981 on a bread board and extract hsync and ysnc signals from the SNES. This is a very basic operation but was good practice for my first attempt at bread boarding stuff.
Obviously I can use hsync and vsync to count scanlines, which is half the information I need. Now I need a clock source for generating ppu clocks, which are not available from the display port. If I sync the clocks (and clock generation) using hsync, Then sending this to the ADC I should be able to get pixel level resolution.
It's slow going but so far so good.
It turns out I made the most basic of basic mistakes and didn't have my probe attenuation matching my scope setting, so the actual RGB voltage peak to peak is ~1.5 volts not ~0.15 volts, oops!
So now instead of attenuating to ~75% and being able to use differential input I have to attenuate to only ~33% to fit in the 500 mV peak to peak limit of the MAX1003, disaster! I tested this using basic potentiometers to divide the voltage down and got the above picture. The voltage signal is still technically DC so nothing weird happens, but the potentiometers must have some small internal capacitance because the voltage drop takes longer than for the original signal. I think this is still in time for pixel to pixel transitions, but it's pretty close.
Aside from that the signals are still pretty clean after attenuating so I will continue with my original plan.
I still have the option to tap the digital RGB on the ppu, but I would really prefer if I didn't have to touch the console so I will press on with this for now.
Now I need a clock source, split the csync signal, and to convert to digital color.
Hello, Alyosha! If you want to blow the dust off GBA, here is some new TAS material of Serious Sam Advance. User movie #639126240314619325
I - It is the most botted movie of all time, and it will remain so for the longest time hereafter. My botting machine unfortunately broke down, and I decided to downsize it (sell RAM) to recoup the investment. It will take a few years for me to buy something at a larger scale.