6.1.3 Getting refSPAD calibration results
The function VL53LX_GetCalibrationData() allows to get all calibration data. The returned structure
VL53LX_CalibrationData_t contains another structure called VL53LX_customer_nvm_managed_t which contains
the 8 refSPAD calibration parameters:
• ref_spad_man__num_requested_ref_spads: this value is between 5 and 44. It gives the number of SPADs
selected
• ref_spad_man__ref_location: this value can be 1, 2 or 3. It gives the location of the SPADs in the reference
area.
• 6 additional parameters gives the good spad maps for the location selected:
– global_config__spad_enables_ref_0
– global_config__spad_enables_ref_1
– global_config__spad_enables_ref_2
– global_config__spad_enables_ref_3
– global_config__spad_enables_ref_4
– global_config__spad_enables_ref_5
6.1.4 Setting refSPAD calibration data
At each startup, after an initial boot, customer field application can load the refSPAD calibration data after
VL53LX_DataInit() function is called, by using VL53LX_SetCalibrationData().
It is better to get the entire calibration structure by calling VL53LX_GetCalibrationData(), modify the 8 parameters
described in previous section and call VL53LX_SetCalibrationData().
6.2 Crosstalk calibration
Crosstalk (XTalk) is defined as the amount of signal received on the return array which is due to VCSEL light
reflection inside the protective window (coverglass) added on top of the module for aesthetic reasons.
Depending on the coverglass quality, this parasitic signal can affect the device performances. VL53L3CX has a
built in correction that allows to compensate this problem.
Crosstalk calibration is used to estimate the amount of correction needed to compensate the effect of a cover
glass added on top of the module.
The output of the crosstalk calibration contains many parameters that define the crosstalk model, as described in
Section 6.2.3 Getting crosstalk calibration results.
6.2.1 Crosstalk calibration function
The following dedicated function is available for crosstalk calibration:
VL53LX_PerformXTalkCalibration(&VL53L3Dev);
Note: This function must be called in second position in the calibration procedure, after refSPAD calibration is done,
and before offset calibration.
6.2.2 Crosstalk calibration procedure
To perform the crosstalk calibration, a target has to be placed at a distance of 600mm from the device.
Crosstalk calibration should be conducted in a dark environment with no IR contribution.
After VL53LX_DataInit() and VL53LX_PerformRefSpadManagement() functions are called, the dedicated
calibration function has to be called, using: VL53LX_PerformXTalkCalibration(&VL53L3Dev).
When these functions are called, crosstalk calibration is performed and the crosstalk correction is applied by
default.
UM2778
Crosstalk calibration
UM2778 - Rev 1
page 15/25
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