Android加速度计是毫秒还是微秒？

Question

So I'm getting accelerometer data using HTC EVO. I get values like this for time.

967454610000 967534902000 967613576000 967692434000

The difference between these values is around 80,000,000. The documentation says: "The value must be one of SENSOR_DELAY_NORMAL, SENSOR_DELAY_UI, SENSOR_DELAY_GAME, or SENSOR_DELAY_FASTEST. or, the desired delay between events in microsecond ."

So I'm using SENSOR_DELAY_UI and I assumed that the times are microsecond. That does not make sense tho cause that means that each time interval is about 80 seconds. It would make more sense if they were in nanoseconds which would mean the time interval is about .08 seconds or 12 data was captured in every second. But then it would contradict the documentation. Does anyone know what is the time interval?

Thanks a lot!

Answer 1

So I'm getting accelerometer data using HTC EVO. I get values like this for time.

967454610000 967534902000 967613576000 967692434000

Are those values obtained from the timestamp member of a SensorEvent instance ? If so, those times are in nanoseconds according to the documentation. So the delay isn't about 80,000,000 microseconds, it's actually about 80,000 microseconds, or 0.08 seconds, giving a frequency of 12.5 events per second.

Answer 2

Sensor delay for Android UI is 60,000 micro-seconds. Which is 0.06 seconds and hence frequency is 16Hz. Similarly for GAME, the delay is 20,000 micro-seconds (50 Hz).

Specifying a delay constant in microseconds (40,000) should give us 25Hz but it doesn't. According to documentation, this is just a hint for minimum delay and sensor manager will deliver values faster than that. According to my experiment, specifying 40,000 microseconds gives 50Hz frequency.