Duplicate Sensor Values with SensorAPI

Problem description
When subscribing to continuous sensor updates, SensorOutputWriter sleeps for a fixed amount of time, then sends out the most recent sensor data. This sensor data may be exactly the same as was sent out previously.

Steps to reproduce

$ termux-sensor -s Pressure -d 10
{
  "BMP280 Pressure": {
    "values": [
      1004.2263793945312,
      0,
      0
    ]
  }
}
{
  "BMP280 Pressure": {
    "values": [
      1004.2263793945312,
      0,
      0
    ]
  }
}
{
  "BMP280 Pressure": {
    "values": [
      1004.2263793945312,
      0,
      0
    ]
  }
}
{
  "BMP280 Pressure": {
    "values": [
      1004.230224609375,
      0,
      0
    ]
  }
}
{
  "BMP280 Pressure": {
    "values": [
      1004.230224609375,
      0,
      0
    ]
  }
}
{
  "BMP280 Pressure": {
    "values": [
      1004.230224609375,
      0,
      0
    ]
  }
}

Notice the duplicate values.

Expected behavior
No duplicate values.

I'm not sure what the intention was with the -d flag.

Android allows you to configure a sensor's update rate, and it notifies you when a sensor's value changes.

I think SensorAPI should:

• Allow the user to set a sensor's update rate
• Print a new sensor value whenever Android notifies SensorAPI that a sensor's value has changed

I think this would be a much more useful behavior. I'm currently trying to automate logging of sensor values, and I want to squeeze the maximum performance out of my device's sensors. However, the updates termux-sensors produces are not in-sync with the actual sensor updates.

Additional information

$ termux-info
Updatable packages:
All packages up to date
Subscribed repositories:
https://dl.bintray.com/xeffyr/x11-packages-24 x11/main
https://dl.bintray.com/xeffyr/unstable-packages-24 unstable/main
https://dl.bintray.com/grimler/science-packages-24 science/stable
https://dl.bintray.com/grimler/termux-root-packages-24 root/stable
https://dl.bintray.com/grimler/game-packages-24 games/stable
https://dl.bintray.com/termux/termux-packages-24 stable/main
System information:
Linux localhost 3.18.31-10376601-eng #1 SMP PREEMPT Thu Feb 2 19:51:12 KST 2017 aarch64 Android
Termux-packages arch:
aarch64
Android version:
7.0
Device manufacturer:
samsung
Device model:
SM-G930V

Start with SensorOutputWriter and the SensorAPI behavior exercised by termux-sensor -s Pressure -d 10; trace how the fixed delay selects and emits sensor data. Compare that flow with Android's sensor update notifications and define completion as no repeated values while preserving the requested update-rate behavior.