During the development of my gamepad latency tester, I discovered an interesting pattern: the frequency of button presses or stick movements can significantly affect measurement results. The difference can be 1-2 milliseconds, which is quite significant for precise testing.

An example of how a pause between clicks affects the latency

Observations

When we conduct a test with a stable frequency, say 200 button presses per minute, the results show a consistent latency of around 5ms. However, when changing the frequency to 300 presses per minute, we consistently get different results - either 4ms or 6ms.

Technical Explanation

This phenomenon is most likely related to the gamepad's polling rate. The principle is similar to vertical synchronization in monitors: if you "sync up" with the polling frequency - you get one result, if you don't - you get another.

This can be compared to how V-Sync works: if the frame rate isn't synchronized with the monitor's refresh rate, you get screen tearing. Similarly, when the periodicity of button presses aligns with the gamepad's polling window, we get one set of results, when it doesn't - we get another.

Solution

To achieve more realistic testing, I've implemented a system of random delays between measurements. This simulates the natural variability of human inputs and helps avoid "synchronization" with the gamepad's polling rate.

This innovation should make testing more representative of real-world conditions, where humans never press buttons with perfectly consistent intervals. As a result, we get more objective data about the gamepad's actual latency.

Conclusion

Understanding this effect is crucial for developing accurate gamepad testing methods. In future versions of the tester, I plan to continue improving the methodology to obtain the most objective results possible.

P.S. This is my personal observation and hypothesis that requires further research and verification.