VL53L4CX Two API function problems

[sctz]

Hi,

When I get the data returned by VL53L4CX, I have two problems.

1:About"VL53LX_get_device_results()"

The API function "VL53LX_get_device_results()" takes a lot of time. My MCU is 32MHZ and the operation of this function takes me 13ms. Is this time acceptable?

2:About"vl53lx_tuningparm_reset_merge_threshold"

When the distance of the measured object changes, the data obtained by the L4CX is delayed for a few cycles before the new distance is obtained. There are several cycles of error reporting (ErrorCode: sometimes 7,sometimes 255) or old distance before getting the new data. Looking in the manual, it seems that this can be improved by decreasing the"vl53lx_tuningparm_reset_merge_threshold", but even if I change it to 0, it doesn't change anything, am I using it wrong?

Thanks.

[Zhiyuan.Han]

Hi 

For the 1st question, I test with STM32 F401(84Mhz) VL53LX_GetMultiRangingData() with 400khz I2C, which include VL53LX_get_device_results(), it's around 3ms -4ms from my side, your reading time is a bit long, but still reasonable.  

For the 2nd question, this tuning parameter is used to decide when to trig a new round of signal merge, the sensor will compare current and previous return signal difference, if you set a big value, the scene need have a significant change to trig, that's why the user manual suggest to set a smaller value if you want to improve the latency, please have a try with different value than 0. 

 

Br

Zhiyuan.Han

[sctz]

Hi,

Thank you very much for your reply, I understand the first question.

About the second question, I still have some questions.

Can you help explain "trig a new round of signal merge"?
Does it mean that if there is a big difference between the current measurement and the previous one, the current measurement output will keep the result of the previous measurement? And if I change "vl53lx_tuningparm_reset_merge_threshold" ，I can adjust the trigger threshold for this?

 

Thanks

 

[Zhiyuan.Han]

Hi 

Yes, your understanding is correct, this tuning parameter is a threshold to decide when to trig a new round of signal accumulation (or saying reset the signal accumulation). with a fix target, the return signal variation will be very small, this means it will not reset the signal accumulation. But if the scene changed suddenly, ex. a target mov into/out FOV suddenly, the return signal rate will change a lot compare with previous frame, sensor will detect the return signal rate variation bigger than the threshold, the signal accumulation buffer will be reset. 

 

Br

Zhiyuan.Han