5 Ranging results
5.1 Available data
An extensive list of target and environment data may be output during ranging activities. The following table
describes the parameters available to the user.
Table 3. Available output using VL53L8CX sensor
Element Nb bytes (RAM) Unit Description
Ambient per SPAD 256 Kcps/SPAD
Ambient rate measurement performed on the
SPAD array, with no active photon emission, to
measure the ambient signal rate due to noise.
Number of targets
detected
64 None
Number of detected targets in the current zone.
This value should be the first one to check to
know a measurement validity.
Number of SPADs
enabled
256 None
Number of SPADs enabled for the current
measurement. A far or low reflective target will
activate more SPADs.
Signal per SPAD
256 x nb targets
programmed
Kcps/SPAD
Quantity of photons measured during the VCSEL
pulse.
Range sigma
128 x nb targets
programmed
Millimeter
Sigma estimator for the noise in the reported
target distance.
Distance
128 x nb targets
programmed
Millimeter Target distance
Target status
64 x nb targets
programmed
None
Measurements validity. See Section 5.5 Results
interpretation for more information.
Reflectance
64 x number targets
programmed
Percent Estimated target reflectance in percent
Motion indicator 140 None
Structure containing the motion indicator results.
The field 'motion' contains the motion intensity.
Note: For several elements (signal per spad, sigma, …) access to data is different if user has programmed more than
1 target per zone (see Section 4.10 Multiple targets per zone). See example codes for more information.
5.2
Customize output selection
By default, all VL53L8CX outputs are enabled. If needed, the user can disable some sensor output.
Disabling measurements is not available on the driver; it must be performed in the ‘platform.h’ file. The user can
declare the following macros to disable outputs:
#define VL53L8CX_DISABLE_AMBIENT_PER_SPAD
#define VL53L8CX_DISABLE_NB_SPADS_ENABLED
#define VL53L8CX_DISABLE_NB_TARGET_DETECTED
#define VL53L8CX_DISABLE_SIGNAL_PER_SPAD
#define VL53L8CX_DISABLE_RANGE_SIGMA_MM
#define VL53L8CX_DISABLE_DISTANCE_MM
#define VL53L8CX_DISABLE_TARGET_STATUS
#define VL53L8CX_DISABLE_REFLECTANCE_PERCENT
#define VL53L8CX_DISABLE_MOTION_INDICATOR
Consequently, the fields are not be declared in the results structure, and the data is not transferred to the host.
The RAM size and I2C/SPI size are reduced.
To ensure data consistency, ST recommends to always keep ‘number of target detected’ and ‘target status’
enabled. It allows filtering the measurements depending of the target status (refer to Section 5.5 Results
interpretation).
UM3109
Ranging results
UM3109 - Rev 1
page 15/20
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