Detection thresholds confusion

[BBald.1]

A couple of questions.

First there seems to be some conflicting comments. In the vl53l5cx_plugin_detection_thresholds.h file there is the following statement in regard to the mathematical operators for multiple checkers. "Please note that the first checker MUST always be a OR operation." Then in the file Example_9_detection_thresholds.c there is the statement " Please note that the first one must always be set with a mathematic_operation VL53L5CX_OPERATION_NONE." I've tried the example with both OR and NONE and it works either way.

The seconds question is I can't seem to get the AND operation to work. I want it trigger when the distance is between 200 and 400 mm AND the SIGNAL_PER_SPAD_KCPS > 10. When I use the VL53L5CX_OPERATION_AND operator it never triggers. If I change it to look for VL53L5CX_TARGET_STATUS == 5 instead of VL53L5CX_SIGNAL_PER_SPAD_KCPS > 10 then it triggers, but none of the zones have a distance between 200 and 400 mm. Looks like it is triggering when the distance is between 50 and 100 mm AND status == 5.

Thank you

[John E KVAM]

if you look at the definition of the VL53L5CX_OPERATION_NONE and the OR, you will find they are both defined as Zero.

But you have a point about the documentation.

And we believe you have found a legitimate bug in the AND condition software.

We are trying to track that down.

I'll repost when a solution is published.

(Turns out this is proving to be a bit tricky.)

• john

[John E KVAM]

I think we found the problem...

It seems this is a pointer bug in ULD. Can you please review my test change that I verified:

File name: vl53l5cx_plugin_detection_thresholds.c

Function name: vl53l5cx_set_detection_thresholds()

Line 168 :

change from

switch(p_thresholds->measurement)

to

switch(p_thresholds[i].measurement) 

in this section of code we are scaling the input parameter to the format required by the chip.

and by using a pointer (and not incrementing it) we applied the wrong scaling factor to all the interrupt checkers.

• john

[BBald.1]

John,

That seems to have got it. The AND is now working.

Thanks!

Barry

[Thomas.PEROTTO · Accepted solution]

Hi John, BBald.1,

We just committed the driver version 1.1.2 on ST.com with this patch.

Thanks for finding and correcting this issue.

Regards,

Thomas