• grrrr
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  • Registered: 2024-01-24
  • Posts: 2

Topic: Digiface AVB grandmaster

Hi,
i have a strange problem with my Digiface AVB (firmware v255, driver 4.10).
With some AVB devices in the network (and on the same Presonus SW5E switch), the Digiface is the only device that doesn't select the same Grandmaster as the others, but rather its own PTP clock. The Grandmaster clock is sourced from a Cisco 3150 switch over the Presonus.

Sometime, the Digiface locks to the Grandmaster, then streaming also happens for a short time, but for the most part, it is faulty in this configuration. If it doesn't find the Grandmaster, the AS_PATH data is also empty.

The RME AVB Tool on the same network is stable.
Interestingly, i realized that the two RME devices have quite different PTP settings (communicated over the AVB_INTERFACE descriptor), regarding priorities.

Find screenshots from Hive here:
https://owncloud.grrrr.org/index.php/s/BZfXwtAL5bkQc7Q

Any clues?

thanks, Thomas

2 Reply by damarco (edited by damarco 2024-01-24 18:21:54)

  • Registered: 2022-01-23
  • Posts: 27

Re: Digiface AVB grandmaster

The Digiface is itself a clock master. Of course it can't have a path. The cause cannot be determined from the pictures. This happens if no master is found, then it switches to its own clock. This happens when the device detects that the clock is bad or PTP sync packets are lost. Then the Digiface deselects the GM and switches to its own clock.

But it could also be because Digiface is being re-initalized -> USB Errors.

Users say they have general problems with the Presonus SW5E switch.

Priority 1 is used for the BCMA algorithm. GM A is better if it is smaller than a GM B. A value of 0xFF decimal 255 means that the PTP instance is not GM capable. The values are specified as profiles in the standard IEEE 801.2AS. The decimal value 248 is specified.

Priority 2 is also used for the BCMA and the decimal value 248 is correct.

  • grrrr
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Re: Digiface AVB grandmaster

Hi, thanks for the answer.
I have not yet had problems with the Presonus switch, apart from the fact that all other AVB devices except the Digiface are totally stable all the time.
It is also strange that the two RME devices behave differently in that respect and also that their PTP parameters are different.
I have also put an RME avb_tool screenshot into the cloud linked folder.

  • Registered: 2008-06-26
  • Posts: 151

Re: Digiface AVB grandmaster

You did not mention the avb software version number. It may be a good idea to check for updates. The current version for DIF AVB is: 0.9596 (Windows) and 0.9597 (mac OS).

  • Registered: 2008-06-26
  • Posts: 151

Re: Digiface AVB grandmaster

There is a new Version of the Dif AVB firmware available: v260. It includes a bugfix in the BMCA and improves the stability of the audio streaming in case of a GM change. A GM change may leed to dropouts since the GM clock is missing for some time / there is a leap in time.