3 Replies Latest reply on Jan 10, 2019 11:57 PM by abhinavg_21

    What is iso endpoint

    MaXi_1246331

      The datasheet says the transfer rate is guaranteed for iso endpoint. I do not really understand the guaranteed transfer rate. Is it mean the transfer rate will not be lower that a certain value or be a constant from time to time? In my application, FPGA  gets data from ADCs in a constant data rate.  FPGA write data to the slave fifo P port of FX3 with the constant date rate. FX3 send the data to the host computer. In this application, should I use iso endpoint to ensure the transfer data from FX3 to host be a constant and avoid the full of the in buffer? Is it better to use iso endpoint than bulk endpoint.

      In another application. the host computer send data to FPGA through FX3. FPGA produce waveform according to these data. If the host send data with a varying rate, the endpoint may become empty and the waveform thus become incorrect. In this application, is the iso endpoint better?

        • 1. Re: What is iso endpoint
          abhinavg_21

          Hi,

           

          The basic difference between ISO EP and BULK EP is that in ISO provides guaranteed USB bandwidth, but data might get corrupted sometimes whereas in BULK EP it will guarantee delivery of data but latency might vary according to the errors in the link. Both EPs performs CRC check but in ISO EP there will not be any retry if data is found corrupted. Isochronous transfers occur continuously and periodically. They typically contain time sensitive information, such as an audio or video stream. If there were a delay or retry of data in an audio stream, then you would expect some erratic audio containing glitches. However if a packet or frame was dropped every now and again, it is less likely to be noticed by the listener.

           

          Thanks & RegardsAbhinav

          • 2. Re: What is iso endpoint
            MaXi_1246331

            Is the guaranteed bandwidth good for my mentioned applications?

            • 3. Re: What is iso endpoint
              abhinavg_21

              Hi,

               

              As described above, ISO will give you a guaranteed USB bandwidth but data may corrupt sometimes. So if you are okay with that go ahead with ISO end point.

               

              Thanks & Regards

              Abhinav