Re: Motor record: motion relative to .RBV

[Kevin Peterson via Tech-talk <tech-talk at aps.anl.gov>]

Marco,

The motor record will tell device support to send relative move commands 
with displacements relative to the readback position, instead of 
absolute move commands, to the controller if the following conditions 
are met:

1. RTRY != 0
2. RMOD != "In-Position"
3. UEIP = YES or URIP = YES

The default RMOD setting is not "In-Position", so all that should be 
required is to set RTRY > 0 and set UEIP = YES (assuming ERES is set 
correctly).

It is important to note that not all drivers implement relative moves 
(motorPIGCS2 is the first that comes to mind).

Kevin


On 10/28/22 14:40, Marco A. Barra Montevechi Filho via Tech-talk wrote:
> Hello all!
>
> Im reading through the EPICS motor record to search for a field similar 
> to .RLV. If i understand correctly, the .RLV will do something similar 
> to summing the caputted value to .VAL instead of directly putting it 
> into .VAL.
>
> Is there a field that sums itself with .RBV instead and then puts this 
> value into .VAL?
> Example of expected behavior:
>
> caget MOTOR.RBV
> MOTOR.RBV         0.5
> caget MOTOR.VAL
> MOTOR.VAL         2  #Lets say that for some reason .VAL and .RBV are 
> not in sync.
>
> caput MOTOR.MISTERIOUS_FIELD 0.5
>
> #wait for some time...
>
> caget MOTOR.RBV
> MOTOR.RBV            1
> caget MOTOR.VAL
> MOTOR.VAL             1
>
> Sorry if the question is trivial but i couldnt find anything in the 
> documentation. Thanks!
>
> Marco