Experimental Physics and
Industrial Control System

Patrick Thomas <[email protected]> · Fri, 24 Jul 2009 05:22:11 -0700

Hi,

I would like to try to implement the following pseudo code as a device

support function for a motor. Basically, when called, it turns the motor

on, checks to see if the motor was on, tells the motor to move to a

position, waits for it to finish or time out, turns the motor off,

checks to see if the motor is off, then checks to see if the current

position is the one that was requested. The functions that it calls will

be provided by driver support. The question I have is that I want it to

immediately start moving to a new position if a new value is entered in

the associated ao record field, even if the motor is already in motion.

Is it possible to check for changes in the value field of the record

from this function? Do I need to start this function as a new thread,

set PACT to true, and then set it to false at the end of the thread? How

would the thread pick up on the fact that the record value field has

changed?

Another question I have is, that in driver support, in the init

function, I will open up a socket connection and spawn a thread which

constantly polls the motor for its status, ie current position,

trajectory mode, motion done, etc. This data will be written to a

structure which is available to the device support. However, when device

support calls other driver support functions which communicate with the

motor over the same socket connection, how do I ensure that these don't

collide with the functions that are constantly polling?

Thank you,
Patrick

request_move_to_absolute_position( record val field )
{
   motor_on();

   if (read_motor_on != true)
   {
       print error;
       return;
   }

   move_to_absolute_position( record val field );

   while ( (motion_done_status != true) and (timeout != true) ) {
       if ( record val field changes ) {
           move_to_absolute_position( record val field );
           reset timeout;
       }
   }

   motor_off();

   if (read_motor_off != true)
   {
       print error;
   }

   if (read_actual_position() != record val field) {
       print error;
   }

   return;
}

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System