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android / platform / external / walt / 098c8fb
commit098c8fb26dedf92edcb8b077e9c4dadeb51450ad[log] [tgz]
authorTai Kuo <taikuo@google.com>Thu Jun 18 12:45:10 2020 +0800
committerTai Kuo <taikuo@google.com>Fri Jun 19 15:26:36 2020 +0800
tree7336bb04f595404dae6bed38cf0ec0840b3f6521
parent1f4104148dbcca978b792d68dadc414872576955 [diff]
Revert "Convert sync_clock_jni to Android.bp"

This reverts commit d4e5f84fbee26cf0c8bf99e807539fbbcf159dd4.
ndkbuild does not support Android.bp yet.

Bug: 149721303
Test: `mma -j48` in android/WALT
Change-Id: Iaf060a65dc95e74f7d59338c4b740e49cf2a8035
Signed-off-by: Tai Kuo <taikuo@google.com>
2 files changed
tree: 7336bb04f595404dae6bed38cf0ec0840b3f6521
  1. android/
  2. arduino/
  3. docs/
  4. hardware/
  5. ios/
  6. pywalt/
  7. server/
  8. AUTHORS
  9. CONTRIBUTING.md
  10. CONTRIBUTORS
  11. LICENSE
  12. METADATA
  13. MODULE_LICENSE_APACHE2
  14. OWNERS
  15. README.google
  16. README.md
README.md

WALT Latency Timer

DISCLAIMER: This is not an official Google product.

WALT is designed to measure the latency of physical sensors and outputs on phones and computers. It can currently perform the following measurements:

  • Tap latency - time from the moment a finger-like probe touches down (or up) on the screen until the kernel timestamps an ACTION_DOWN (or ACTION_UP) event. This physical contact with the screen is timed using an accelerometer mounted on the probe.
  • Drag latency (scroll).
  • Screen draw latency - using a photodiode that detects whether the screen is black or white.
  • Audio output and microphone latencies.
  • MIDI input and output latencies

The WALT app for Android can be installed from Google Play or downloaded in the releases section; the iOS app must be built from source.

WALT photo

Notes

  • Hardware build instructions can be found in this repository under hardware/.
  • Clock synchronization details are described here.
  • The Android/iOS device and Teensy clocks have a tendency to diverge due to differing clock frequencies. This means they will go out of sync after several minutes. The workaround is to use the app to re-sync the clocks. Some, but not all tests in the app will sync the clocks when starting a measurement.
  • Python code used to communicate with WALT from Linux and ChromeOS can be found here.