User Manual

DocID029105 Rev 1 17/26
UM2039 API useful additional functions
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6 API useful additional functions
6.1 Overall timing budget
The timing budget is the time allocated by the user to perform one range measurement. The
API takes care of splitting this timing budget into dedicated sub steps in the ranging process.
The user only has to set the overall timing budget in micro seconds, and the function
allocates the timings internally. A check is performed to know which part of the scheduler is
enabled or disabled, in order to maximize Final Range timing budget.
VL53L0X_SetMeasurementTimingBudgetMicroSeconds()and
VL53L0X_GetMeasurementTimingBudgetMicroSeconds()
The default timing budget value is 33ms, while the minimum is 20ms.
Example of use:
Status =
VL53L0X_SetMeasurementTimingBudgetMicroSeconds(pMyDevice,66000) sets
the overall timing budget to 66ms.
Note: Increasing the timing budget increases the range measurement accuracy.
That is: x N on timing budget => standard deviation / square root of N.
For example is the timing budget is increased by a factor of x 2, then the range
measurement standard deviation decreases by square root of 2.
6.2 Limit settings
User can enable/disable limit checks and values.
Disabling or relaxing these limits can allow longer ranging, in this case, standard deviation
will increase and measurement outliers will be received by the Host.
Applicable limits are:
• Sigma:
VL53L0X_CHECKENABLE_SIGMA_FINAL_RANGE
Sigma is the time difference (shift) between the reference and return SPAD arrays. As
Sigma represents time of flight and this translates to distance, this parameter is expressed
in mm.
• Return Signal Rate
VL53L0X_CHECKENABLE_SIGNAL_RATE_FINAL_RANGE
Return signal rate measurement, expressed in MCPS. This represents the amplitude of the
signal reflected from the target and detected by the device.
• Range Ignore Threshold
VL53L0X_CHECKENABLE_RANGE_IGNORE_THRESHOLD
Signal rate minimum threshold. Measurements with signal rates below this value are
ignored. This ensures that false measurements are not made due to reflection from the
housing.