2 Replies Latest reply on Jun 27, 2018 2:50 PM by v0ynich_3529131

    Read ADC on both rising a falling edge

    v0ynich_3529131

      Hello,

       

      I would like to interface an dual channel ADC through the GPIF port on the FX3. The ADC has an output clock which must be used to sample the output data. One channel must be sampled in the rising edge of this clock and the other channel on the falling edge. What is the best way to implement this? Let's say that this clock is running at 50Mhz

       

      Best regards

        • 1. Re: Read ADC on both rising a falling edge
          ayarema_2483746

          From the description it doesnt sound like a direct connection to FX3 is the best idea, however if that is what is really desired what you could do is find an external PLL to take the ADC clock as input and produce a clock that is 2x of that. So that way the FX3 is running at 100Mhz phase aligned with the original clock. Then at the FX3 just sample the data normally and in software decode CH1 and CH2 because they simply will be alternating Odd samples will be Ch1, Even samples will be CH2 etc.

           

          Or the other way is to have an FPGA or something similar between the FX3 and the ADC.

           

          Edit: Also check out this post GPIF II DDR Mode

           

          -Andriy

          • 2. Re: Read ADC on both rising a falling edge
            v0ynich_3529131

            Thanks for the tip but I would prefer to go to the DDR approach.

            The PLL approach adds more hardware and it seams more prone to get the channels out of sync if there is a cycle slip in the PLL.

             

            Let's see what I can dig on this GPIF II DDR Mode

            Is this DDR a true DDR? Does it mean that you can take 2x 32bit per clock cycle at 100MHz? Or do you need to lower the clock frequency to 50MHz?

             

            Best regards,

            Mário