sensing_sensor_value_header Struct Reference

sensor value header More...

#include <sensing_datatypes.h>

Data Fields
uint64_t	base_timestamp
	Base timestamp of this data readings, unit is micro seconds.
uint16_t	reading_count
	Count of this data readings.

Detailed Description

sensor value header

Each sensor value data structure should have this header

Here use 'base_timestamp' (uint64_t) and 'timestamp_delta' (uint32_t) to save memory usage in batching mode.

The 'base_timestamp' is for readings[0], the 'timestamp_delta' is relation to the previous 'readings'. So, timestamp of readings[0] is header.base_timestamp + readings[0].timestamp_delta. timestamp of readings[1] is timestamp of readings[0] + readings[1].timestamp_delta.

Since timestamp unit is micro seconds, the max 'timestamp_delta' (uint32_t) is 4295 seconds.

If a sensor has batched data where two consecutive readings differ by more than 4295 seconds, the sensor subsystem core will split them across multiple instances of the readings structure, and send multiple events.

This concept is borrowed from CHRE: https://cs.android.com/android/platform/superproject/+/master:\ system/chre/chre_api/include/chre_api/chre/sensor_types.h

Field Documentation

base_timestamp

uint64_t sensing_sensor_value_header::base_timestamp

Base timestamp of this data readings, unit is micro seconds.

reading_count

uint16_t sensing_sensor_value_header::reading_count

Count of this data readings.

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The documentation for this struct was generated from the following file:

• zephyr/sensing/sensing_datatypes.h