This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DS90CR287 Camera Link Transmitter

Other Parts Discussed in Thread: DS90CR287

We are trying to set up a camera using your Camera (Channel) Link transmitter chip and are having trouble. We are using the DS90CR287 85 MHz Camera Link Transmitter. This is a student project and we are not masters of Electrical Engineering by any measure. But we have designed a camera to output pixel data from a sensor, through your Camera Link transmitter, out to a 3rd party Frame Grabber. We have verified that our camera sensor is outputting data correctly to the Transmitter. We just can't get the Transmitter to link up with the Frame Grabber's receiver. We are running out of ideas, and can't tell where the problem lies. We are running our camera at 32MHz, and the CL chip is rated for these speeds. 1. We have followed convention for Camera Link input and output for pixel order. 2. We have measurements of each LVDS pair, and they do not behave as expected. They change depending on if a cable is connected or not, and while some lines display good differential behavior, some other lines seem like they are only noise. The chip is properly powered and grounded, and lines are isolated. 3. We aren't seeing a 7x multiplication of the clock speed on any of the LVDS lines. 4. LVDS pairs dont seem to be +-, rather they are both sending signals at roughly the same voltage level of 1.6 V. The Frame Grabber we are using has the matching reciever chip for our transmitter, and it is proven to work. The problem lies with our transmitter side, and we can't tell what it is based on your documentation. We can provide schematics for our DS90CR287 hookup, PCB layouts, anything you need. It is getting to crunch time here and we are absolutely at a loss. Any help would be appreciated!

  • Hi Jed,

    This sounds very similar to a post by Zach in this forum. I referenced him to the following materials to explain how the Channel Link devices work:

    Channel Link Design Guide 

    LVDS Owner's Manual 

    The symptom you describe, regarding the plugging and unplugging of the cable goes back to transmission line basics. When the cable is plugged in the LVDS drivers of the CR287 are connected to the termination on the frame grabber PCB. When you remove the cable the LVDS drivers of the CR287 see an open circuit.  In transmission lines, driving an open circuit will result in a double voltage. You can find some more information about this on Wikipedia, search for reflection coefficients or transmission line theory.

    As for your debug:

    If your frame grabber isn't able to recover the data, here are a few things to check:
    1. Is the deserializer in your frame grabber/FPGA locked to the correct clock frequency?
    2. If you probe the LVDS differential lines (at the frame grabber side, and across the 100 ohm differential termination resistors) do you have an open eye diagram. See the LVDS owner's manual for what a good eye diagram should look like.
    3. If steps 1 and 2 are OK, then look at the inputs to the CR287. Probe each LVCMOS clock and data input. No input should dip below ground.
    One more thing to note, is that you should be using a high impedance, low capacitance differential probe to examine the LVDS lines.
    Mike Wolfe
    DPS APPS / SVA
  • Jed ... Did you manage to fix your Camera Link issues ?

    Brahim