• Hardware

  • Trying to use STROBE and FSYNC for OAK-1 Camera

We are trying to sync via HW an OAK-1 camera (IMX378, AF) with a flash lighting.

We opened the enclosure and connected the STROBE and FSIN test pads on the PCB to an oscilloscope, as shown below:

Following the docs, we first attempted to measure the Strobe Signal against GND. Unfortunately, we only observed a noisy 50Hz line signal, even though the camera was on and capturing frames. Note: oscilloscope probe was previously tested and worked fine.

After some research, we couldn't find the schematic due to proprietary hardware constraints. However, we did find a schematic for these signals from another camera on this thread, but it didn't help.

We also tried adding a pull-up resistor and attempted to locate an isolated ground without success.

After all this work, we have some doubts:

  1. Does this hardware have an interface that isolates these signals? If so, where should we get the isolated GND from?

  2. What is the voltage range for the FSIN input?

  3. What is the GPO pin for?

  4. Do we need to configure the camera on software to activate the strobe signal or the FSIN input?

Thanks for your assistance,

Alan

    AlanElkin Does this hardware have an interface that isolates these signals? If so, where should we get the isolated GND from?

    The pads should all be relative to the common ground. No need for isolation. The issue is that STROBE is actually not exposed for rolling-shutter sensors.

    AlanElkin What is the voltage range for the FSIN input?

    1.8V (not sure about the range +/-)

    AlanElkin What is the GPO pin for?

    GPO seems it can be driven high/low by writing to sensor registers (functionality not exposed through depthai)

    AlanElkin Do we need to configure the camera on software to activate the strobe signal or the FSIN input?

    You need to set the FrameSyncMode to INPUT:
    cam_A.initialControl.setFrameSyncMode(dai.CameraControl.FrameSyncMode.INPUT)

    This will make the camera wait for FSIN signal.

    From the email discussion: flash during appropriate time will require a well timed pulse synced with the sensor's internal clock. May be possible to script something out, by making use of the frame event as in luxonis/depthai-pythonblob/main/examples/MonoCamera/mono_preview_alternate_pro.py

    Thanks,
    Jaka

              6 days later

              jakaskerl

              Thanks for your reply.

              Just to clarify: GPO and STROBE cannot be used with the OAK1 camera for rolling shutter sensors, correct?

              And, to confirm our procedure for syncing the camera and flash during tests, we need to:

              1. Set FrameSyncMode to INPUT.
              2. Set the camera to 20 FPS (as an example)
              3. Send a square periodic signal of 20Hz (matching the previously set FPS) with a LOW value of 0v and a HIGH of 1.8V through FSIN pad (referenced to GND).

              Is all this correct? Is there anything else we need to do?

              PS: I'll take a look at the example to do a syncing via software only, using frame's timestamps. Thanks

                  AlanElkin Just to clarify: GPO and STROBE cannot be used with the OAK1 camera for rolling shutter sensors, correct?

                  Correct.

                  AlanElkin Is all this correct? Is there anything else we need to do?

                  Should be good to go I think.

                  Thanks,
                  Jaka