PTP Issue with Lib_TSN in Xcore 200

[lokesh327]

Hi,

I try to use the lib_tsn library for xcore 200 using i2s audio input.

When I am connecting two devices to test how the ptp is working, I noticed that the correction time is always 0 in pdealy req and followup messages.

From the previous version of gptp module (SW_AVB 5.2 framework), noticed that

"timestamp_to_network(pTxReqHdr->originTimestamp, cur_time_ptp);"

command is missing which updates the correction actually.

Did anyone had this issue or am I doing something wrong.

Thanks
Lokesh

[Thomas]

Hi Lokesh
pDelay requests should not have an origin timestamp. This is fixed in version 6 onwards.

Correction field is just a nanosecond fraction in 802.1AS point-to-point pDelay messages. It's common to set it to zero.
In fact, the AVnu compliance test plan issues a warning when it's non zero to remind you that you might have some leftover code in there if your implementation is a port of 1588, where I think the correction field is used differently.

Here are the references to the 802.1AS spec:
Section 8.4.3 and figure 8-2 (correction mechanism), section 11.4.2.4 and table 11-5 (correction field).

Best Regards, Thomas

[lokesh327]

Hello Thomas,

Thanks for the information.

In this case can we synchronize two xmos devices one with PTP version from lib_tsn (7.0.1) and another device with older XMOS frame work version 5.2 and module_gptp.


Thanks
Lokesh