5. RealSense Cameras
The Realsense depth cameras are special in that they cannot be triggered like the Pointgrey cameras. Instead their internal clocks can be synched up with an external signal. There are a few important consequences of this:
- If the external signal is removed or never present the Realsense will revert to its own clock and become unsynched.
- If the external signal is not close enough to what the Realsense expects, for example you tell the Realsense to operate at 30Hz but provide a 27Hz signal, the Realsense will crash.
The signal must be very stable with minimal jitter. It should consist of pulses of 1.8v 50 - 100 us long. Firmware version v5.10.3 is the most forgiving version and will still work with a somewhat poor signal however newer firmware v5.11.01 is much more stable overall. Operating at lower frame rates will allow you microcontroller to get closer to the expected frame rate and make synching more reliable.
- Intel Realsense D435, although in theory the D415 would also work.
- Realsense SDK
- Realsense ROS Driver check out the external sync branch.
Both D400 Realsense cameras include an RGB camera. This camera uses a rolling shutter sensor and in the case of the D435 is on a separate vision unit from the infrared cameras. This RGB camera cannot be synched like the depth camera and as such is not useful for visual-inertial odometry applications.