Experimental Physics and
Industrial Control System

Updates on testing:

So, i did the suggested test alternating CNEN (between 0 and 1), VELO (1 and 2), DHLM (4 and 5) and DLLM (-4 and -5) fields. Not because they have any particular physical meaning, but to understand if the behavior is similar in several motor record fields. I tested at least twice for each field.

I append the code for testing below and attach the logs as files. What i found interesting:

1 - In some tests, the first print from callback function is the first value in which the field was before changing (i.e., before the first caput in the code is called). In some other tests, the first print is the value only after being changed via caput. This suggests to me that the "add_callback" method by itself sometimes triggers a callback and sometimes doesnt. I remember having observed this behavior before with other PVs.

2 - In several parts of the log, callback prints the same value twice. This is more or less predictable: DLLM field for example seems to almost always trigger two callbacks at once, but there are cases like the end of Loop 6 in CNEN_LOG1 where it seems out of the pattern: CNEN almost always triggers only one callback, but in this loop i got two at once.

What i understand:

1 - some fields typically (but not always) trigger callbacks twice and some dont. 
2 - the add_callback method may or may not immediately call the callback function, even if no value has been altered in the PV.

What i dont understand:

1 - What are the causes of intermittence in behavior 1, such as observed in end of loop 6? 

2 - What are the causes of intermitence in behavior 2?

Generic question: can these things be controlled or is it just something i have to live with?