Re: check what is caput doing

[Ralph Lange <ralph.lange@gmx.de>]

On 10/09/2014 10:30, zunbeltz.izaola@essbilbao.org wrote:
> The outuput of cainfo is
> LEBT:LEBT:PS:STH1:OPER:CurrSP
>      State:            connected
>      Host:             10.30.0.10:5064
>      Access:           read, write
>      Native data type: DBF_DOUBLE
>      Request type:     DBR_DOUBLE
>      Element count:    1

Full access - no firewall and/or access security issue. Good.

> > What value are you trying to write to which field of what record type?
> This is the current setpoint of a power supply.
> The IOC db file contains this information
> record(ai,"LEBT:PS:STH1:OPER:CurrSP"){
>    field(INP,"LV:LEBT:PS:STH1:OPER:CurrSP CP")
>    field(DESC,"PS EXT Voltage")
>    field(DESC, "LEBT STH1 Current SP")
> }
>
> I guess that I am trying to change the INP field which has no access
> permission according to the Record Reference Manual, isn't it?
> In this case how is possible that the value can be changed with the CSS GUI?
> Should have the record a VAL field?

This input record is configured (through its INP setting) to get its 
value from LV:LEBT:PS:STH1:OPER:CurrSP, whenever that record's value 
changes.

Writing to the INP field will change the record's configuration to point 
to another source for the value.

Writing to the VAL field is probably closer to what you want, but still 
- your caput changes the value and processes the record, then during 
that processing the record does what it is configured to: it reads the 
value from the configured location LV:...:CurrSP.

Bottom line:
If you configure your input record to pull its value from another 
location, you cannot change the value by writing to it, and vice versa.

Hint:
Maybe the simulation mode (again: described in the Application 
Developers Guide and the Record Reference Manual) is able to achieve 
what you want. It allows you to switch your input record into simulation 
mode (.SIMM), where it will not use the configured INP link, but a 
special simulation link or value (.SIOL) to fetch its value.

> Sorry if they are trivial questions; but I new to EPICS.

I would suggest participating at a training. The next public one is held 
as part of the EPICS collaboration meeting end of October in Saclay 
(Paris), France. There are also people and companies that can provide 
in-house training, if that is more appropriate.

Good luck!
~Ralph