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android / platform / external / walt / ed462e937cd99e9aaee98613c4e3e0469145d719
commited462e937cd99e9aaee98613c4e3e0469145d719[log] [tgz]
authorAndrew Lehmer <alehmer@google.com>Thu Apr 27 11:24:39 2017 -0700
committerAndrew Lehmer <alehmer@google.com>Thu Apr 27 11:24:39 2017 -0700
tree11234e8c4682a3a0114b1d4df6135c1222b1b3e4
parente76dcf96b0c451e46cddfa695de8feeb92533937 [diff]
walt: fix internal build system errors

Although external/walt is not part of a full build, the JNI it defines
includes an Android.mk which is somehow picked up in test builds. The
original code contains several unused parameter warnings that get
converted to errors during test builds, and this change cleans those up.

Bug: 37744894
Test: `mma -j48` in android/WALT/app/src/main/jni/ builds cleanly
Change-Id: I354df5d168bc4550df19258035fdb33ac7249831
3 files changed
tree: 11234e8c4682a3a0114b1d4df6135c1222b1b3e4
  1. android/
  2. arduino/
  3. docs/
  4. hardware/
  5. ios/
  6. pywalt/
  7. server/
  8. AUTHORS
  9. CONTRIBUTING.md
  10. CONTRIBUTORS
  11. LICENSE
  12. 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.