BLDC component with 8i20 - how to get to work?

Ok, sounds very legit, I definitely can try that. How does the "q" mode work? Bldc man page is not very descriptive on this. I guess I have to disconnect index-enable pin and observe bldc.0.offset-measured. Anything else?

With runaway I mean fast motion in the opposite direction until following error is triggered, so I guess that does correspond to "continuous motion". Yes, I am sure that encoder signal is good because I have old servo drives still in the cabinet that export the signal to LinuxCNC and this machine was introduced to LinuxCNC 3-4 years ago and never have been issues with encoder feedback (there have been no changes so far how the encoder signal is delivered to LinuxCNC).

I tried "q" mode.
I am pretty sure that there is something missing in the procedure that I was doing.
I commented out 2 lines that link bldc index-enable pin and sets encoder-offset value.
Started LinuxCNC, let the init process finish, observe bldc.0.offset-measured value, write it down, close LinuxCNC and repeat 2 more times.
Values that I got: 39984, 24798, 49060. Since that is 1000 PPR encoder that would give 4000 counts per shaft turn (1000 counts per electric turn), then those differences of ten thousand counts do not make sense to me.
And what does this offset-measured mean exactly? Distance in encoder counts between what 2 locations? One should be electrical zero of rotor, but what is the other if index is ignored in "q" mode?
Or should I place the motor on index manually and then start LinuxCNC and let it do the init process?

Can you
1. use you original (qi) setup
2. decouple the motor from the linear axis
3. set the following error limits to huge numbers
4. See if the d term causes a multi-turn runaway

 

Here you go:

In essence: BLDC component in "qi" mode, ferror set at 5000 mm and belt removed. I can jog the motor back and forth with D = 1, but it immediately runs away as soon as set D = 4 and press "test".

I have attached INI and HAL files

Honestly it sounds like the initial angle is still not correct

You might try adjusting the offset by small increments
and checking how high you can set the D term

Also the negative init current seem strange

Another possibility is checking whether raising the servo
thread rate (to say 4 KHz) helps

Should I try with motor only or put the belt back on (e.g. the lack of load - is it going to highlight the issue no)?

Negative init is for reversing direction of motion during init process. I tried setp bldc.0.rev 1 (I am not sure what does this do) but it seemed to me that the direction did not change.