Apple Studio Display (M7768) boot signal - Potentially Related?

[TitaniaEXE]

Hello, I've been looking into the ADC Apple Studio Display, model M7768. This is Apple's last CRT, and it uses ADC as it's connector. It's possible to split it back into VGA + USB + Power (+LED +Soft Power), either by a converter or simply splicing the wires. However, the Display will only "boot" if it's connected to a G4-G5 era Mac, as it needs some sort of boot signal.

Now, some known things about this monitor:

• It accepts DDC over USB, to calibrate it. You can audibly trigger the degauss with it.
• It can be woken up even when connected to a VGA/DVI-A port on a proper mac, if the ADC cable is split to it.
• Per /u/crt09, the signal is probably coming over DDC.

Is there any possibility the boot signal this monitor expects is related to the signals these IVAD boards use?

[qbancoffee]

I'm not sure if ti uses the same sort of sequence but I wouldn't doubt it. The best way to know is if you can sniff the comms between the two when starting it up. Do you have a way of sniffing the comms?

[TitaniaEXE]

I currently lack a compatible Mac system to connect it to, or a logic analyzer. However, using Linux it is possible to transmit arbitrary i2c/DDC signals, so it should be possible to try the signals. Given that the monitor is active enough to transmit EDID and handle DDC over USB, it would seem that it only needs a "start up" signal, as the device is already awake enough to handle those.

[TitaniaEXE]

Using an HDMI to VGA adapter, the monitor presents four i2c registers at the bus:

• 3a
• 50 (contains EDID for the monitor)
• 55
• 5a

I reckon I could use i2cset for write_byte_data, and i2cget for read_byte, but I am not certain what would replicate simple write_byte.