6 Customer factory calibration functions
In order to get benefit of full performance of the device, VL53L3CX driver includes calibration functions to be run
once at customer production line.
Calibration procedures have to be run to compensate part to part parameters that may affect the device
performances.
Calibration data stored in the host have to be loaded in VL53L3CX at each startup using a dedicated driver
function.
Three calibrations are needed: refSPAD, crosstalk and offset.
The order the calibration functions are called as follows:
1. refSPAD
2. crosstalk
3. offset
The three calibration functions can be done in sequential mode or individually. When run individually, the previous
step data have to be loaded before running calibration.
6.1 RefSPAD calibration
The number of Single photon avalanche diode (SPAD) is calibrated during Final Module Test at ST. This part to
part value is stored into NVM and automatically loaded in the device during boot.
This calibration allow to adjust the number of SPADs to optimize the device dynamic.
However, adding a cover glass on top of the module may affect this calibration. We recommend that the customer
performs again this calibration in the final product application.
The same algorithm running at FMT is applied when this function is called: the algorithm searches through the 3
locations 1 (1x attenuated SPADs), 2 (5 x attenuated SPADs) and 3 (10 x attenuated SPADs). Number of SPADs
choosen is done to avoid signal saturation.
6.1.1 RefSPAD calibration function
The following function is available for SPAD calibration: VL53LX_PerformRefSpadManagement(VL53LX_DEV
Dev)
Note: This function must be called first in the calibration procedure.
The function can output 3 warnings messages :
• VL53LX_WARNING_REF_SPAD_CHAR_NOT_ENOUGH_SPADS
Less than 5 Good SPAD available, output not valid
• VL53LX_WARNING_REF_SPAD_CHAR_RATE_TOO_HIGH
At end of search reference rate > 40.0 Mcps Offset stability may be degraded.
• VL53LX_WARNING_REF_SPAD_CHAR_RATE_TOO_LOW
At end of search reference rate < 10.0 Mcps. Offset stability may be degraded.
6.1.2 RefSPAD calibration procedure
No particular conditions have to be followed for this calibration, except that no target should be placed just on top
of the device.
Time to perform this calibration is only few milliseconds.
This function has to be called after VL53LX_DataInit() function is called.
UM2778
Customer factory calibration functions
UM2778 - Rev 1
page 14/25
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