Error in communication

[svenhaitjema]

Dear All,

Thank you for fixing the code related to the connection issues. The PLC&TIA14 is now able to connect to the p-net software, however I have the following observation making me believe something is still off:

The PLC status alternates between 'connected' and 'connection error'.

The error reporting on the p-net side is:
[ERROR] PPM(479): iocs_len is zero
[ERROR] PPM(479): iocs_len is zero
[ERROR] PPM(479): iocs_len is zero
ABORT err_cls 253 err_code 5

OR

[ERROR] PPM(479): iocs_len is zero
[ERROR] PPM(479): iocs_len is zero
[ERROR] PPM(479): iocs_len is zero
ABORT err_cls 0 err_code 6

This seems to be resolvable by setting the 'max missed packet count' to 16 at the PLC side. So it appears a timing problem.

Kind regards,

Sven-Erik Haitjema

[pyhys]

Normally the p-net stack on Linux sends a cyclic data frame approx every 3 ms. When this increases to around 7 ms (due to load), the Simatic PLC sends an alarm indicating that the timing requirements not are met. Then the cyclic communication is shut down for a few seconds, until a new start-up happens.

We are looking into using the PREEMPT_RT patches to improve the Linux real time properties.

[pyhys]

You need to tweak the Linux real time properties to fulfil the Profinet timing requirements. We have started to document this on https://rt-labs.com/docs/p-net/linuxtiming.html