Hacker News Reader

Comment by driverdan | Hacker News Reader

I wonder what the margin of error is on marking when the button push is made. Controller button range of travel makes it nearly impossible to know exactly when the electrical connection takes place from a video.

I think it'd be better to touch wires together or something more obvious to reduce the margin of error.

View on HN

It probably depends on how the button is debounced as well. Software and physical debounces are both generally tuned for at least a few milliseconds and potentially over ten milliseconds of latency.

A better trigger could be built by interfacing a microcontroller over USB HID and having it send a simulated keystroke or button press at the same time as turning on an LED.

I think you're being generous. I've had microswitches that needed a good 20-25 mSec to fully debounce. Good quality sealed switches (like Cherry) too, not badly plated counterfeit stuff.

I'd assume that Carmack was going by the same distance that the key was depressed in the reference frame for each test.

The variance on that would be about one frame, would would add up to 4 ms for each test. However, since the input device did not change between the experimental equipment, it's a constant error that would be added into every test, making that a wash.

There was a controller mod that addressed this exactly [1].

[1] http://youtu.be/XkiyxzvsAYo

I have seen test rigs where the button switches are in series with an LED - the LED lights essentially instantly, and it is very obvious on-camera when that circuit is closed.

Reply on news.ycombinator.com