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Associate II
October 18, 2024
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VL53L1 Dynamic SPAD Selection Question

  • October 18, 2024
  • 1 reply
  • 1232 views

Hi!
I have two short questions regarding the dynamic SPAD selection happening on the VL53L1 sensor discussed previously here:

- Is there a minimum number of SPADs after the selection? As in, by utilizing a 4x4 region, should I expect no oscillations (the ones I showed on the other post) due to the selection?
- Is there a direct way to find which specific SPADs are being used after the selection? So I could use it to troubleshoot if the weird distance measurements were caused by it or other factors I didn't take into account.

Thanks in advance!

Best answer by John E KVAM

You might still get occasional oscillations, but by limiting the max number of SPADs they should not be as wild. 

The minimum I have seen is something like 3.2. But the API rounds for simplicity. 

The location of the enabled SPADs is called a SPAD Map, and we removed it from the API as it is pretty useless. 

Your issue is due to the DSS algorithm choosing too many SPADs. We can tell by the Number of SPADs and the super high Signal rate. But that algo is buried deep in the sensor, and we don't have any control over it except to limit the max number of SPADS. 

- john

1 reply

John E KVAM
John E KVAMBest answer
ST Employee
October 18, 2024

You might still get occasional oscillations, but by limiting the max number of SPADs they should not be as wild. 

The minimum I have seen is something like 3.2. But the API rounds for simplicity. 

The location of the enabled SPADs is called a SPAD Map, and we removed it from the API as it is pretty useless. 

Your issue is due to the DSS algorithm choosing too many SPADs. We can tell by the Number of SPADs and the super high Signal rate. But that algo is buried deep in the sensor, and we don't have any control over it except to limit the max number of SPADS. 

- john