Smoothing Motor Readback

Several Galil systems use analogue feedback as the encoder, this is effectively an absolute encoder (so no need to rehome etc) but the readback can be noisy and this has caused issues in the past with setpoints looking like they are drifting. The WISH instrument is an example.

We did look at smoothing the values within an EPICS db using the compress record etc. and linking this to an alternative motor readback, but it turned out the jaws were so noisy it swamped the Galil and we had to add smoothing there.

To set this up for MTR0105 on WISH for example you would:

• have a non-zero max retries count - default is 10
• set a readback delay, currently using 5 seconds
• set readback resolution to 1 (we have handled this in the _EPOS_CALC record)
• set a readback link value - for MTR0105 on WISH this is IN:WISH:MOT:MTR0105:EPOS_AV CP MS
• set use encoder to no
• set use readback to yes

Setting use encoder to no before enabling readback is probably a better sequence of operations, but not crucial. If you set readback to yes it automatically sets encoder to no, but i had a case when it seemed to get a bit confused. If it does make sure values are correct and then just restart ioc and autosave will apply them correctly. Bear in mind that these are settings and so autosave at 30 second intervals, so don't restart too soon after a change