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Continuous or Burst Mode on the LIDAR-Lite V3 and V3HP
As part of the update to the signal processing for the LIDAR-Lite V3HP several command and control registers have been modified or eliminated. In most instances, there will be no impact on users from these changes.
However, the “Continuous” or “Burst” mode functions, controlled by registers 0x45 and 0x11, which have been removed in this version may impact users of previous versions of LIDAR-Lite who have been operating the sensor in continuous mode, such as in scanning applications. Also, those users wanting to operate the sensor at high measurement speeds will benefit from this application note.
These functions were removed because operating in continuous mode was not ideal for fast scanning. Between the V2 and V3 versions of the sensor, the status bit output behavior was modified so that it indicated the device was busy while performing burst acquisitions. Therefore, while operating in continuous mode, the sensor always appears busy to the host processor. Polling the sensor’s distance registers under this condition resulted in values that were not correlated with a specific measurement start time. Alternatively, using a hardware based interrupt indication isn’t always a practical option, particularly in rotational scanners, where adding an additional slip ring connection would increase hardware complexity and cost.
Because you can no longer use continuous mode with the LLV3HP, you should use the following approach for fast scanning applications. This approach is also a more reliable method for fast scanning applications with previous versions of the sensor:
- Initiate new measurement command
- Immediately read the distance registers, obtaining the previous measurement results while the new measurement is occurring (remember, measurement data stored in the sensor is valid until new measurement concludes)
- Perform other actions while polling the Status bit until it indicates idle
- Repeat steps 1 through 3
This method is slightly more I2C overhead, but allows more efficient polling if you know a bit about your measurement time (which depends on maximum acquisition count settings). You also know exactly when that measurement begins.
For more information and sample code, refer to our GitHub repository at the link below: