User manual

Functional description VL6180X
22/79 DocID026171 Rev 6
return signal rate 0.5 ms after the start of every measurement. If it is below the ECE
threshold, the measurement is aborted and an ECE error is flagged.
Figure 13. Early convergence estimate (ECE)
ECE is enabled by setting bit 0 of SYSRANGE__RANGE_CHECK_ENABLES{0x02D}. If
enabled, the ECE threshold must be specified. To set the ECE threshold 20% below the
minimum convergence rate, the ECE threshold is calculated as follows:
The 16-bit ECE threshold should be written to
SYSRANGE__EARLY_CONVERGENCE_ESTIMATE{0x22}. For example, if
SYSRANGE__MAX_CONVERGENCE_TIME{0x1c} is set to 30 ms, the ECE threshold is 204.
If the return count is less than 204 after 0.5 ms, the measurement will be aborted.
Note: The optimum value for the ECE threshold should be determined in the final application.
2.8.2 Range ignore
In a system with cover glass, the return signal from the glass (cross-talk) may be sufficient
to cause the system to converge and return a valid range measurement even when there is
no target present. The range ignore feature is designed to ensure that the system does not
range on the glass. (Cross-talk is described in more detail in Section 2.12.2).
The ignore threshold is enabled by setting bit 1 of
SYSRANGE__RANGE_CHECK_ENABLES{0x02D}. If enabled, the ignore threshold must be
specified. In the follow example, the ignore threshold is set 20% above the system cross-
talk:
A range ignore error will be flagged if the return signal rate is less than the ignore threshold.
SYSRANGE__RANGE_IGNORE_VALID_HEIGHT should be set to 255.
Note: The optimum value for the ignore threshold should be determined in the final application.
time
Return
count
convergence threshold
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max.
convergence
ECE (0.5 ms)
measurement
aborted
converged
ECE
threshold
ECE threshold
80% 0,5× 15360×
SYSRANGE__MAX_CONVERGENCE_TIME (in ms)
----------------------------------------------------------------------------------------------------------------------------------------=
SYSRANGE__RANGE_IGNORE_THRESHOLD{0x26} cross-talk (Mcps) 120%×=