ST VL6180X - Reference Array Statistics

DocID026571 Rev 1 9/27
AN4545 Other ranging outputs
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3.2.2 Return convergence time
Register RESULT__RANGE_RETURN_CONV_TIME {0x7c} contains the time in µs it took
for the return array on VL6180X to settle or converge on a target distance during the range
measurement.
Note: If Return convergence time is equal to the max convergence time, then VL6180X was not
able to detect a target during the last measurement.
{0x7c} is a 32-bit register.
3.2.3 Return signal count
Register RESULT__RANGE_RETURN_VCSEL_COUNT {0x6c} contains the number of
counts recorded during the convergence time
(a)
from the return array during the range
measurement.
The following equation show the relationship between count, signal rate and convergence
time.
Note: {0x6c} is a 32-bit register.
3.2.4 Return ambient count
Register RESULT__RANGE_RETURN_AMB_COUNT {0x74} contains the number of
ambient counts recorded during the convergence time
(a)
during the range measurement.
The ambient counter is only active for 1/6th of the convergence time, hence the count value
must be multiplied by 6.
See the following equation of how to convert the ambient count into Mcps.
Note: {0x74} is a 32-bit register
3.3 Reference array statistic
3.3.1 Reference signal rate
Register RESULT__RANGE_REFERENCE_RATE {0x68} contains the signal rate from the
reference array recorded during the range measurement.
To convert the reference rate into Mcps, read {0x68} and divide the value by 128.
Note: {0x68} is a 16-bit register.
a. The count register continues to increment till both return and reference array have converged. This means for
the Convergence time [µs], the maximum value between {0x7c} and {0x80} should be used in the equation.
Under normal operation, {0x7c} should be the larger number value.
Return Signal Rate [Mcps]
Return Signal Count
Convergence Time [µs]
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Return Ambient Rate [Mcps]
Return Ambient Count 6×
Convergence Time [µs]
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