VL6180 datasheet(22/73 Pages) STMICROELECTRONICS

22 / 73 page

Functional description

VL6180

22/73

DocID024986 Rev 14

Figure 14. ECE

ECE is enabled by setting VL6180x_RangeSetEceState() and configured with

VL6180x_RangeSetEceFactor(). This allows the user to change the ECE threshold from

the default of 15% below minimum convergence rate. As shown by the example below.

If the max convergence time is set to 30 ms (using

VL6180x_RangeSetMaxConvergenceTime()), then the ECE threshold is 196. That is, if

the return count is less than 196 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 2.15.2).

The ignore threshold is enabled with VL6180x_RangeIgnoreSetEnable(). If enabled, the

ignore threshold and valid height must be specified, this is set with

VL6180x_RangeIgnoreConfigure().

A range ignore error will be flagged if the return signal rate is less than the ignore threshold.

Note:

The optimum value for the ignore threshold and valid height should be determined in the

final application.

2.8.3

Signal-to-noise ratio (SNR)

SNR function not yet implemented in API.

In high ambient conditions range accuracy can be impaired so the SNR threshold is used as

a safety limit to invalidate range measurements where the ambient/signal ratio is considered

too high.The default ambient/signal ratio limit is 10 (i.e. an SNR of 0.1) which is then

encoded in 4.4 format as follows:

SYSRANGE__MAX_AMBIENT_LEVEL_MULT{0x2C}

= 10 x 16 = 160

ECE threshold

85% 0.5 10240



Max convergence time (in ms)

--------------------------------------------------------------------------------

VL6180 Datasheet(PDF) 22 Page - STMicroelectronics