light_sensor_calibration

Source code: light_sensor_calibration.py

Calibration test for light sensor (a chamber is needed).

Description

This is a station-based test which calibrates light sensors. The test controls a light chamber to switch light intensity between different light preset and reads the value from the light sensor of a DUT.

The calibration method is linear regression. The test samples multiple data points (e.g., LUX1, LUX2) and find out a new linear equation to fit the validating data point (e.g., LUX3). The calibrated coefficients scale factor and bias will be saved to the VPD.

The default chamber connection driver is PL2303 over RS232. You can speicify a new driver to chamber_conn_params. You also need to provide the chamber_cmd with which a station can command the light chamber.

Besides the arguments, there are still many configurations in the light_sensor_calibration.json. For examples:

{
  "version": "v0.01",
  "light_seq": ["LUX1", "LUX2", "LUX3"],
  "n_samples": 5,
  "read_delay": 2.0,
  "light_delay": 6.0,
  "luxs": [40, 217],
  "validating_light": "LUX3",
  "validating_lux": 316,
  "validating_err_limit": 0.2,
  "force_light_init": false

}

The most important entries are luxs and validating_lux. They are the preset illuminance value of a light chamber fixture. You need a lux meter to evaluate the preset light settings from the light chamber fixture to get these values. After you have these values, don’t forget to update the runtime configuration by calling cros.factory.utils.config_utils.SaveRuntimeConfig('light_sensor_calibration', new_config) so that you have the correct preset light information. There are many things that influence the preset light value of the light chamber. It could be the unstable elecrtic environment or if the light chamber’s bulb is broken.

Test Procedure

This is an automated test. Before you start the test, prepare the physical setup and calibrate the light chamber itself by a lux meter:

1. Connects the station and the DUT.

2. Connects the station and the light chamber.

3. Press start test.

4. After finishing the test, disconnects the station and the DUT.

Dependency

• A light chamber with at least three luminance settings.

Examples

To automatically calibrate the light_sensor with the given chamber_cmd, add this into test list:

{
  "pytest_name": "light_sensor_calibration",
  "label": "Light Sensor Calibration",
  "related_components": [
    "test_tags.TestCategory.AMBIENTLIGHTSENSOR",
    "test_tags.TestCategory.VPD"
  ],
  "args": {
    "control_chamber": true,
    "assume_chamber_connected": true,
    "chamber_cmd": {
      "LUX1": [
        [
          "LUX1_ON",
          "LUX1_READY"
        ]
      ],
      "LUX2": [
        [
          "LUX2_ON",
          "LUX2_READY"
        ]
      ],
      "LUX3": [
        [
          "LUX3_ON",
          "LUX3_READY"
        ]
      ],
      "OFF": [
        [
          "OFF",
          "OFF_READY"
        ]
      ]
    }
  }
}

To debug and use a mocked light chamber:

{
  "pytest_name": "light_sensor_calibration",
  "label": "Light Sensor Calibration With Mocked Chamber",
  "related_components": [
    "test_tags.TestCategory.AMBIENTLIGHTSENSOR",
    "test_tags.TestCategory.VPD"
  ],
  "args": {
    "control_chamber": true,
    "assume_chamber_connected": false,
    "chamber_cmd": {
      "LUX1": [
        [
          "LUX1_ON",
          "LUX1_READY"
        ]
      ],
      "LUX2": [
        [
          "LUX2_ON",
          "LUX2_READY"
        ]
      ],
      "LUX3": [
        [
          "LUX3_ON",
          "LUX3_READY"
        ]
      ],
      "OFF": [
        [
          "OFF",
          "OFF_READY"
        ]
      ]
    },
    "mock_mode": true
  }
}

Trouble Shooting

If you found error related to load configuration file:

• This is probably your runtime config format is incorrect.

If you found error connecting to light chamber:

1. Make sure the chamber and station are connected.

2. Make sure the dongle is correct one. If you are not using the dongle with PL2303 driver, you need to provide one.

If you found the calibrated coefficients are skewd:

1. This is probably you don’t calibrate the light chamber recently.

Test Arguments

Name	Type	Description
control_chamber	bool	(optional; default: False) Whether or not to control the chart in the light chamber.
assume_chamber_connected	bool	(optional; default: True) Assume chamber is connected on test startup. This is useful when running fixture-based testing. The OP won’t have to reconnect the fixture everytime.
chamber_conn_params	dict, str, None	(optional; default: None) Chamber connection parameters, either a dict, defaults to None
chamber_cmd	dict	A dict for name of lightning to a [cmd, cmd_response].
chamber_n_retries	int	(optional; default: 10) Number of retries when connecting.
chamber_retry_delay	int	(optional; default: 2) Delay between connection retries.
mock_mode	bool	(optional; default: False) Mock mode allows testing without a fixture.
config_dict	dict, None	(optional; default: None) The config dictionary. If None, then the config is loaded by config_utils.LoadConfig().
keep_raw_logs	bool	(optional; default: True) Whether to attach the log by Testlog