VL53L8CH More CNH Bins for One CNH

[JGarrettW]

Hello,

I am using the 53L8A1A to evaluate the VL53L8CH with the MZAI_EVK_v1.0.1 software. For my application, I need high CNH resolution for as long a histogram as possible, but for only one histogram. Because of that, I aggregated down to one row and one column with the following configuration settings.

  CNH_4x4_ONECNH:
    StartType: 0
    Resolution: 16
    RangingPeriod: 500
    ZoneMode: 2
    GlareFilter: 0
    ExtendedMode: 2
    cnhStartX: 0
    cnhStartY: 0
    cnhMergeX: 4
    cnhMergeY: 4
    cnhCols: 1
    cnhRows: 1
    cnhNumBins: 75
    cnhSubSample: 1
    isDefault: false
    isVisible: true

I see in the CNH_Data_Size sheet within the MZ-AI_Configuration Excel sheet that the MZ-AI GUI limits the cnhNumBins parameter to 75. The calculator says that the data size for more bins than that does work, however.

Is there a reason that the parameter is limited to 75 and, if not, is there an easy way for me to change that limit?

Thanks,

Garrett

[John E KVAM · Accepted solution]

I checked with the developer. 75 is a limit of the PC-based GUI. It is not a limit of the sensor. 

See if you can do your evaluation with the 75 bin limit, then switch to your board and get away from that PC-based limitation.

It will work.

- john

[RogerM]

*** News flash ***
An updated software package for the VL53L7CH / VL53L8CH is now available for download on ST.com.
One of the changes is to allow the MZAI EVK GUI to capture up to 144 CNH bins.
This update does not change the maximum memory of CNH data that can be captured and uploaded to the host, but it removes the 75 bin limitation to allow configurations such as described by the opening poster to upload all available bins.

The update also includes a number of bug fixes and corrections to the ULD driver and STM32 firmware project.

Packages are available here:

https://www.st.com/en/embedded-software/stsw-img043.html

[RogerM]

I should add one extra detail for anyone working with such configurations in which they wish to capture all the the available CNH bins....
If you set the cnhNumBins to 144 and then capture frames of data you will find that half of the frames of data contain only 128 bins of valid data, with the last 16 bins containing zeros (value of exactly 0.000000) .
This is a consequence of the way VCSEL timing is managed on the device. Slightly different timing is used on alternate frames which limits the number of histograms bins that are captured on every other frame.  Since it is extremely, extremely unlikely that real histogram data will contain multiple values of exactly zero if you see these values in the CNH data you can know that only 128 bins contain valid data.