Walt: A device for measuring latency of physical sensors and outputs

I wish every developer had one of these. When you think about it, it's crazy that our devices don't have built-in APIs for measuring this stuff. The latencies are all known exactly at the time the various pieces of hardware are designed, but when the system is integrated that information is lost and suddenly there's no way for the software to know exactly when the finger physically touched the screen, or exactly when the pixels start lighting up, or exactly when the speaker will start vibrating.

In most cases it actually takes less time to send a network packet to a server thousands of miles away than it takes to change a single pixel on the local display. Wouldn't it be great if you could measure the display latency as easily as you can run 'ping'?

I get that the accelerometer detects the touch, and that one of the photodiodes detects a screen change, and there's another input for the mic as well. But I don't understand the purpose of the laser/laser photodiode. What is that detecting exactly? Also, where does the output of this thing go and how is it encoded? Does it go back to the device you're testing and does that affect latency?

This reminds me of the Oculus Latency Tester: https://vrwiki.wikispaces.com/Oculus+Latency+Tester

It seems crazy to me that similar things aren't more common. You can't optimize what you can't measure.

Neat, they use a Teensy microcontroller with an accelerometer breakout board from Adafruit for the hardware.