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AM4379: PTP verification

Bartholomew
Prodigy 20 points
Part Number: AM4379

I have two demo boards: each with an AM4379 and an Ethernet interface. Both are running Linux and LinuxPTP.

I'm looking to run an experiment to verify the time synchronization between the two systems. Ideally, I'd like to toggle a GPIO at specific intervals on both cards and measure the time difference using an oscilloscope. However, I'm concerned about software jitter that may introduce delays in the measurements.

Is there some other suggested method for performing a test like this?

Thanks.

  • 0
    TI__Mastermind 40080 points

    Hi,

    Could you please indicate which demo boards (assuming these are TI EVMs?) and the version of the TI SDK that you are using? If you are using the TI SDK root file system and the ethernet port that you are using?  I want to make sure I understand the app that you are using, are you using ptp4l for synchronizing with the host? 

    Here is a link to the documentation that TI provides on PTP.

    Best Regards,

    Schuyler

  • 0 in reply to Schuyler Patton
    Prodigy 20 points

    Hi Schuyler - I'm actually using two of these demo boards (http://www.myirtech.com/list.asp?id=510) with a custom version of Linux.

    I'm using ptp4l for synchronization.

    Thanks,

    Dan

  • 0 in reply to Bartholomew
    TI__Mastermind 40080 points

    Hi Dan,

    For your evaluation I would recommend moving away from the Rico board and purchasing the AM437x-IDK from TI. This is a TI supported board that runs the TI Processors SDK Linux/RT.  This board has an expansion connector J16 that brings out this signal (pr1_edc_sync0_out - J16, pin 18) that will output the PPS signal which is what you to compare with the Grand Master PPS signal when looking for jitter. This is the link to where the board can be purchased:

    http://www.ti.com/tool/TMDSIDK437X

    I need to mention a couple of issues though that you should consider depending on your timeline to production.  Currently as of this post there is an issue with the AM3x/AM4x class processors on generating the PPS signal from the PRU-ICSS. There is a section in the SDK documentation about setting up the PPS signal. In the link below is a description on how to setup the board to provide a PPS output and a known bug with the PRU-ICSS firmware. The note about the issue I am highlighting is at the end of section 4.3.4.2.  At the moment all I can say is that there is a plan to fix this bug but I do not have visibility to when it will be fixed.  Since you are in the evaluation phase it is OK to use the IDK and current SDK as is. I would recommend that before going to production check SDK releases for this PRU issue being resolved.

    http://software-dl.ti.com/processor-sdk-linux/esd/docs/latest/linux/Industrial_Protocols_PTP.html#generating-1-pps

    I will close the thread for now, please mark as resolved unless you have additional questions that we need to answer. When you get the IDK board you can start a new e2e thread on any issues that you run into setting up the PPS signal.

    Best Regards,

    Schuyler