• State
  • Locked Locked
  • Replies 6 replies
  • Subscribers 33 subscribers
  • Views 966 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

ds90ub925 serializer to ds90uh928 deserializer not locking

Christodulos Tsongas
Genius 13285 points


I am trying to connect the two over FPDLink-III and I am having problems using I2C on the 925 and trying to use remote write to the 928.

It seems the serializer cannot communicate to the deserializer. I would like to ask if anyone has some input on how I can get the two to work together.

  • 0
    TI__Genius 14015 points

    Is the system locked? That would be the first thing to check, otherwise the I2C communication will not work. 

    After that, make sure I2C pass-through is enabled on the 925. This is set on register 0x03[3], should be set to 1. Then you should be able to communicate with the 928 remotely. 

    Thanks,
    Jason

  • 0 in reply to Jason Blackman
    TI__Genius 13285 points

    Currently the system is not locking. Any suggestions on how to get the two to lock? I have used the 925 serializer with other deserializers before (the 926 and 948 specifically) and did not have this problem.

  • 0 in reply to Christodulos Tsongas
    TI__Genius 13475 points

    Christodulos

    Are you using, or do you have access to the TI evaluation boards for the '953 and '928?   As a first step, I would establish a lock between the two EVMs and become familiar with the tools for reading and writing via the I2C ports.   Next I would substitute one side of your prototype system for the appropriate EVM - for example, use the DS90UB925 EVM to drive your display, and again, see if you can establish a reliable link.

    This should help to isolate the problem to the serializer, the deserializer or the cable.

    Mark

  • 0 in reply to Mark Sauerwald88474
    TI__Genius 13285 points
    Mark,

    I am using the EVMs for both the '928 and '925. The tool I have been using to read/write to the EVMs is the Analog LaunchPAD GUI via I2C-USB. Currently I can R/W to the '925 with the GUI when directly connected to it. However, the '925 does not recognize the '928 is connected to it via two SMA cables. Similarly, I can communicate over USB-I2C with the '928 but only when directly connected. But when connected to the '928 it does recognize that a serializer is connected, but I cannot access the remote registers due to the error 'UNKOWN TX'.

    I know the cables work properly as I have used them on other EVMs and I know the '925 works with all other EVMs except the '928.
  • 0 in reply to Christodulos Tsongas
    TI__Genius 13475 points

    Christodulos

    Both the 925 and 928 EVMs have options to either use the SMA connectors or a Rosenberger HSD connector for twisted pair cable.  The default is for the HSD connector - please make sure that the boards are configured to use the SMA connectors (you can connect the sma directly to an oscilloscope input, and when you apply power to the EVM you should see a signal coming from both the serializer and the deserializer).

    Assuming that you are working with the SMA connectors, make certain that your two SMA cables are exactly matched in length - the serial data rate going out of the '925 is almost 3Gbps, so the UI is about 350ps in width.   A small mismatch in cable lengths can introduce enough cable length mismatch to prevent the 928 from being able to lock to the signal.

    Mark

  • 0 in reply to Mark Sauerwald88474
    TI__Genius 13285 points

    Mark,

    Will do. Right now after reading the EVM User Guide for the '928 I noticed the note attached to this post. I have added the 0 Ohm resistors to R3 and R4 but it still did not link. Would the HSD connector (J4) be causing the problem? Since it is not connected to anything I figured it wouldn't cause any problems. Before removing it I will check to make sure the cables are good and transmitting from both devices.

    - Chris