Documentation: document sensortest command

Add documentation for the sensortest system tool which reads data
from sensor drivers via the uORB topic interface.

Signed-off-by: hanzj <hanzj@xiaomi.com>

Documentation/applications/system/sensortest/index.rst

@@ -0,0 +1,212 @@
+===============================
+``sensortest`` sensor test tool
+===============================
+
+Reads data from a sensor driver via the uORB topic interface and prints the
+output to the console. Useful for verifying that a sensor driver is working
+correctly and producing valid data.
+
+Configuration
+=============
+
+Enable the command with ``CONFIG_SYSTEM_SENSORTEST``. This option requires
+``CONFIG_SENSORS`` and ``CONFIG_ENABLE_ALL_SIGNALS``.
+
+The following configuration options are available:
+
+``CONFIG_SYSTEM_SENSORTEST_PROGNAME``
+  Program name for the ``sensortest`` command. Default: ``sensortest``.
+
+``CONFIG_SYSTEM_SENSORTEST_PRIORITY``
+  Task priority. Default: ``100``.
+
+``CONFIG_SYSTEM_SENSORTEST_STACKSIZE``
+  Stack size. Default: ``DEFAULT_TASK_STACKSIZE``.
+
+Usage
+=====
+
+.. code-block:: console
+
+   nsh> sensortest [-i <interval>] [-b <latency>] [-n <count>] <sensor_name>
+
+Options
+=======
+
+``-i <interval>``
+  Data output period in microseconds. Controls how often the sensor is
+  polled for new data. Optional. Default: ``1000000`` (1 second).
+
+``-b <latency>``
+  Maximum report latency in microseconds. When set to a non-zero value,
+  the sensor may batch multiple readings and deliver them at once.
+  Optional. Default: ``0`` (no batching).
+
+``-n <count>``
+  Number of data samples to read before exiting. When set to ``0``,
+  the command runs continuously until interrupted. Optional.
+  Default: ``0`` (unlimited).
+
+``-h``
+  Print help message and exit.
+
+Commands
+========
+
+``<sensor_name>``
+  The sensor node name without the ``sensor_`` prefix and ``/dev/uorb/``
+  path. For example, use ``accel`` to read from ``/dev/uorb/sensor_accel``.
+
+Supported Sensors
+=================
+
+The following sensor types are supported:
+
+.. list-table::
+   :header-rows: 1
+   :widths: 25 25 50
+
+   * - Name
+     - Data Type
+     - Description
+   * - ``accel``
+     - vec3 (x, y, z)
+     - Accelerometer
+   * - ``baro``
+     - valf2
+     - Barometer (pressure, temperature)
+   * - ``cap``
+     - cap
+     - Capacitance
+   * - ``co2``
+     - valf
+     - CO2 concentration
+   * - ``dust``
+     - valf
+     - Dust particle concentration
+   * - ``ecg``
+     - ecg
+     - Electrocardiogram
+   * - ``force``
+     - force
+     - Force sensor
+   * - ``gnss``
+     - gnss
+     - GNSS position
+   * - ``gnss_satellite``
+     - gnss_satellite
+     - GNSS satellite info
+   * - ``gyro``
+     - vec3 (x, y, z)
+     - Gyroscope
+   * - ``hall``
+     - valb
+     - Hall effect sensor
+   * - ``hbeat``
+     - valf
+     - Heartbeat
+   * - ``hcho``
+     - valf
+     - Formaldehyde concentration
+   * - ``hrate``
+     - valf
+     - Heart rate
+   * - ``humi``
+     - valf
+     - Humidity
+   * - ``impd``
+     - valf2
+     - Impedance
+   * - ``ir``
+     - valf
+     - Infrared
+   * - ``light``
+     - valf
+     - Ambient light
+   * - ``mag``
+     - vec3 (x, y, z)
+     - Magnetometer
+   * - ``noise``
+     - valf
+     - Noise level
+   * - ``ots``
+     - vali2
+     - Optical tracking speed
+   * - ``ph``
+     - valf
+     - pH value
+   * - ``pm10``
+     - valf
+     - PM10 particulate matter
+   * - ``pm1p0``
+     - valf
+     - PM1.0 particulate matter
+   * - ``pm25``
+     - valf
+     - PM2.5 particulate matter
+   * - ``ppgd``
+     - ppgd
+     - PPG (photoplethysmography) data
+   * - ``ppgq``
+     - ppgq
+     - PPG quality
+   * - ``prox``
+     - valf
+     - Proximity
+   * - ``rgb``
+     - valf3
+     - RGB color sensor
+   * - ``velocity``
+     - velocity
+     - Velocity sensor
+   * - ``temp``
+     - valf
+     - Temperature
+   * - ``tvoc``
+     - valf
+     - Total volatile organic compounds
+   * - ``uv``
+     - valf
+     - Ultraviolet
+
+Examples
+========
+
+Read accelerometer data at the default 1-second interval:
+
+.. code-block:: console
+
+   nsh> sensortest accel
+   accel: timestamp:1234567890 x:0.12 y:-0.03 z:9.81, temperature:25.50
+   accel: timestamp:1235567890 x:0.11 y:-0.04 z:9.80, temperature:25.51
+   ^C
+
+Read gyroscope data at 100ms intervals, 10 samples:
+
+.. code-block:: console
+
+   nsh> sensortest -i 100000 -n 10 gyro
+   gyro: timestamp:1234567890 x:0.01 y:0.02 z:0.00, temperature:26.00
+   ...
+
+Read temperature sensor with batching enabled:
+
+.. code-block:: console
+
+   nsh> sensortest -b 5000000 temp
+   temp: timestamp:1234567890 value:25.50
+   ...
+
+Notes
+=====
+
+- The command reads from ``/dev/uorb/sensor_<name>`` using the uORB
+  subscriber interface. Ensure the corresponding sensor driver is
+  enabled and the uORB topic is published.
+- The command runs continuously until interrupted with ``Ctrl-C``
+  (``SIGINT``) unless a sample count is specified with ``-n``.
+- The ``-b`` (latency) option controls batching behavior. When set to
+  a non-zero value, the sensor driver may buffer multiple readings and
+  deliver them together, reducing the number of wake-ups.
+- The timestamp field in the output is provided by the sensor driver
+  and uses the system monotonic clock.