Synchronizing cameras with encoder and I/O expansion board

[govindc]

Hello, 

I am trying to acquire simultaneous images from two identical camera link line scan JAI cameras via two NI 1433 boards. Both the cameras are getting their trigger signals from a quadrature wheel encoder.

I am noticing the frame read from the two cameras are not in sync with one camera's frame rate always higher than the other.

Camera 1's frame-grabber board is also getting the encoder's quadrature input via an I/O expansion board. Camera 2, however, does not have an I/O expansion board associated with it. I am keeping track of the frame count from each camera using the pulses out of the smb pin on the frame grabber.

A few of questions on this:

1) Is this a right approach for synchronizing multiple cameras?

2) Do I need another I/O expansion board for the second camera?

3) Is there a way a single I/O expansion board can connect to multiple frame grabbers?

thanks!

[thuyanhl]

Hi,

For Camera 2, are you connecting the encoder signal to the SMB connector in order to trigger the acquisition? 

From this document: http://www.ni.com/tutorial/2989/en/, since you have two different frames grabbers so two separate ADCs, this should be enough for synchronization. 

How much delay are you seeing between the two acquisitions?

[govindc]

Thanks for the reply.The two cameras are getting the encoder trigger signals from the I/O breakout board. However, the NI board for the 2nd camera is not getting the encoder signal right now. I think, this might be the issue. 

I have attached a rough schematic to explain the connections. 

I am assuming, the "Frame Count" signal from the NI I/O board should be in sync for both the acquisition boards as the cameras are being triggered by the same encoder signal. However, since the second framegrabber doesn't have the encoder signal, this assumption might not be valid.

[govindc]

I was able to synchronize the two cameras using RTSI cable. 

Both cameras are now being triggered through camera-link. First camera frame-grabber is getting its encoder signal through the I/O expansion board. The two camera frame-grabbers are connected via an RTSI cable. So, the second camera frame-grabber is  now getting its encoder signal through the RTSI cable.