OV9281 occasional capture timeout on CM3

[lukedempsey]

I am using a CM3 which interfaces with the OV9281 using a custom carrier board.

I have a python script based heavily off of the capture2opencv.py demo - it sits in a while loop capturing images.

I have set my gpu allocation as following:

pi@raspberrypi:~ $ vcgencmd get_mem gpu
gpu=128M

My wiring is a little bit different to a standard CM3 carrier so I have reflected this change in my setup:

self._camera = arducam.mipi_camera()

# define hw wiring for OV9281
self.camera_interface = arducam.CAMERA_INTERFACE()
self.camera_interface.i2c_bus = 0
self.camera_interface.camera_num = 1
self.camera_interface.sda_pins = (28, 0)
self.camera_interface.led_pins = (44, 5)
self.camera_interface.shutdown_pins = (44,5)

self._camera.init_camera2(self.camera_interface)
self._fmt = self._camera.set_resolution(640, 400)
self._camera.software_auto_exposure(enable = True)

My main loop is pretty much identical to capture2opencv.py:

 while True:
            # update frame
            frame = self._camera.capture(encoding = 'i420')
            height = int(self.align_up(fmt['height'], 16))
            width = int(self.align_up(fmt['width'], 32))
            image = frame.as_array.reshape(int(height * 1.5), width)
            image = cv2.cvtColor(image, cv2.COLOR_YUV2BGR_I420)

My problem is that after 50 or so images, the arducam_capture() method will timeout and return a NullPtr. (Definition located here)

My current work around is the very hacky following to catch the buffer being a Null Pointer. It will just reinitialise the camera again and it will operate normatlly for another ~50 images before the error occurs again.

try:
    image = frame.as_array.reshape(int(height * 1.5), width)
except ValueError as e:
    print("ValueError: {}".format(e))
    self._camera.close_camera()
    self._camera.init_camera2(self.camera_interface)
    continue                                         

I have been using this camera with a 3B+ for several weeks and haven't had this problem.

[ArduCAM]

@lukedempsey Would you please post the question on our forum : https://www.arducam.com/forum/

[lukedempsey]

@ArduCAM , I posted here last week. This has got me stumped. Any help would be appreciated.

[lukedempsey]

Didn't explicitly find the root cause, but it was definitely a pebcak. Resolved in the above Arducam forum thread.

[lukedempsey]

Was mistaken, the issue was intermittent enough that it convinced me that it was fixed.

Didn't find the root cause, however a quicker version of my workaround is to reset the resolution, rather than closing and opening the camera again.

[lukedempsey]

however a quicker version of my workaround is to reset the resolution, rather than closing and opening the camera again.

Note to anyone who tries this, I found this wasn't a great way to do it. It would cause the pi to get locked up to a point where it appeared that had shut down

[UCTRONICS]

Hello, Are you sure you can only get 50 pictures each time?