skewjo / syslat_firmware Goto Github PK

Need to try and measure cable delay(propagation) as seen in this post on BlurBusters.

I have no idea how he:

1. Measured the cable lag at all (but I found this paper for measuring coax and skimmed through it.
2. How he was previously measuring times as slow as 4 ms?? I don't actually think it's possible for a signal to transmit that slowly unless you're sending it through mercury or something?

I think this guy may have been conflating "cable lag" with the actual speed of the device... not sure though.

Also just found this comment as well:

Looks like this site was all set to kind of give this thing away, but it was never released.

Also, this guy makes me feel like I have no fucking idea what I'm doing:

My setup is a 240Hz monitor, I'm measuring against a game's titlescreen with vsync off and rtss limiting to 480fps. Probe placed bottom right of the display.

Display at minimum brightness: 28.80ms average over 500 samples.
Display at maximum brightness: 18.53ms average over 500 samples.

A 10ms difference😱

I've been playing with it for some hours and I do get consistent results between trials where all controls are maintained. So long as all hardware is controlled for, relative comparisons of (certain) different software configurations can be made, as well as relative differences from placing the probe on different points on the monitor.

But if the luminance is influencing the results, then the absolute readings cannot be trusted, and readings between different displays are not comparable.

Looking through your code (I am no expert), I see you use an interrupt from the photosensor pin, and have it configured to interrupt on "rising". My guess is that, whatever the board considers to be "rising" is not sufficient for our uses. I suspect the arduino logic is waiting around some arbitrary length of time before it's "certain" we've entered a digital high state,

You probably need to drop the digital ISR approach and read analog data, and implement a calibration mode where the user can record the analog value at "black" and at "white" before running any test.

Then the trigger can be issued at some appropriate value (50% to white? User configurable? Open to discussion here).

Hope this helps!

Is the microcontroller type/sensor type readable from the microcontroller?

The sensor type probably isn't necessary and the code for different sensors is probably different, right(analog vs. digital)?
The microcontroller specs have got to be known to the microcontroller...right?

I believe HID functionality may run at lower level layers of the OS and may achieve different (faster) read/write times, especially for games.