Synchonization between cameras and lidar + lidar data collection timing

kolja

I would like to synchonize my camera with my lidar, both acquiring data at 10 Hz. I figured one way to do it would be using the multipurpose I/O pin. If i se the multipurpose_io_mode to OUTPUT_FROM_ENCODER_ANGLE with 0 degree, sync_pulse_out_pulse_width to 10ms and sync_pulse_out_frequency to 10Hz I would trigger the cameras at the same time the lidar starts collecting its data if I am correct.

However I would like to use the I/O pin to synchonize the timestamp of my lidar with my GNSS. Is there a way to still archive the synchonization in this scenario? If i synchonize the lidar with the gnss does the lidar start collecting data at the start of each second or would it just be depending on when the lidar got powered?
For example: I power the lidar at 9:32:45:3200 AM (hour:minute:second:millisecond) with 10Hz and it would collect the data in the following time interval: 9:32:45:3200 | 9:32:45:4200 | 9:32:45:5200 | 9:32:45:6200 ...
If i power the lidar at the same time but its time synchonized with my gnss would it collect the data instead as in the following interval? 9:32:45:4000 | 9:32:45:5000 | 9:32:45:6000 | 9:32:45:7000 ...

Same question if i would instead synchonize the time of my lidar via ptp. Does the lidar start collecting data at the start of a second or would it be just dependong on when the lidar got powered?

Are there any other ways to synchonize the lidar with my camera?

Thanks for any advice.

JakobGL

Hi Kolja,

multipurpose I/O pin can only serve one purpose at a time, which means if you select this I/O pin to OUTPUT_FROM_ENCODER_ANGLE, this means this pin right now is the output pin and it outputs from the encoder angle. that’s why we have a drop-down list for you to select on the configuration page for multipurpose I/O, you can only select one of those.

In your case, you can use sync_pulse_in pin on the ibox for GNSS time sync. If your GPS is configured correctly and locked correctly, it will start the sync right after power on. Basically, once your time sync is set up with the GPS, your timestamp will be shown as the GPS time, it doesn’t conflict with the output_from_encoder_angle because we have a mechanism to calculate the 10Hz and encoder angle on the motor. Time sync and encoder count are separate things.

Please see the encoder definition in the software user manual below:

“Encoder Count [32 bit unsigned int] - an azimuth angle as a raw encoder count, starting from 0 with a max value of 90,111 - incrementing 44 ticks every azimuth angle in 2048 mode, 88 ticks in 1024 mode, and 176 ticks in 512 modes. Note: the encoder count is redundant with the Measurement ID and will be deprecated in the future.”

Regards,
Jakob