Experimental Physics and
Industrial Control System

Mark Rivers via Tech-talk <tech-talk at aps.anl.gov> · Tue, 29 Jun 2021 16:13:18 +0000

Hi Michael,

> Having a while-loop with an threadSleep is kind of bad coding I think, so I'm wondering if someone knows a better solution?

You can take that code and run it in a separate thread.  You need to call lock() on entrance, and then release the lock around the sleep.

unlock();

epicsThreadSleep(1);

lock();

> PS: I'm also trying to update the motor position during the while-loop (it is the "// Read the current motor position" passage). I see the correct position in the asyn communication but the .RBV value of the motor record won't update. I guess, this can only be done from the poll-function?

The poller should continue to run normally if you run the home sequence in a separate thread and call unlock() as shown above.

Mark

________________________________
From: Tech-talk <tech-talk-bounces at aps.anl.gov> on behalf of Sintschuk, Michael via Tech-talk <tech-talk at aps.anl.gov>
Sent: Tuesday, June 29, 2021 10:13 AM
To: tech-talk at aps.anl.gov
Subject: questions about the motor homing sequence

Hello EPICS-community,

I'm trying to write an EPICS-motor device support for the PEGASUS Rotation- and Linear-Stages from Micos. I'm using the Hydra and Corvus motor-support from the main EPICS-motor module as a template.

I have the following problem when writing the homing sequence for the Rotation-stages: after sending the homing-command string

    sprintf(pC_->outString_, "1 0 %i setsw 1 1 %i setsw 1 0 %i sncal", (axisNo_ + 1), (axisNo_ + 1), (axisNo_ + 1));
    pC_->writeController();

I need to wait until reference-drive finished aka. the motor stopped, so I can switch off the Limit-switches with the following command:

    sprintf(pC_->outString_, "2 0 %i setsw 2 1 %i setsw", (axisNo_ + 1), (axisNo_ + 1));

    pC_->writeController();

So far I could resolve this problem by implementing a while loop with an epicsThreadSleep(1.) asking the controller about its moving bit and once it set to 1 (done), execute the desired command. Here is my complete code of the homing function:

asynStatus SMCpegasusAxis::home(double baseVelocity, double slewVelocity, double acceleration, int forwards)
{
  asynStatus status;
  int done = 0;
  int axisStatus = -1;
  double position = 0.0;
  // static const char *functionName = "SMCpegasusAxis::home";

  status = sendAccelAndVelocity(acceleration, slewVelocity);

  if (forwards) {
    sprintf(pC_->outString_, "1 0 %i setsw 1 1 %i setsw 1 0 %i sncal", (axisNo_ + 1), (axisNo_ + 1), (axisNo_ + 1));
    pC_->writeController();

    // Read the status of this motor
    sprintf(pC_->outString_, "%i nst", (axisNo_ + 1));
    pC_->writeReadController();
    // The response string is an int
    axisStatus = atoi( (char *) &pC_->inString_);

    do
    {
        // Read the current motor position
        sprintf(pC_->outString_, "%i np", (axisNo_ + 1));
        pC_->writeReadController();
        // The response string is a double
        position = atof( (char *) &pC_->inString_);
        setDoubleParam(pC_->motorPosition_, (position / axisRes_) );
        setDoubleParam(pC_->motorEncoderPosition_, (position / axisRes_) );

        // Read the status of this motor
        sprintf(pC_->outString_, "%i nst", (axisNo_ + 1));
        pC_->writeReadController();
        // The response string is an int
        axisStatus = atoi( (char *) &pC_->inString_);

        // Check the moving bit
        done = !(axisStatus & 0x1);
        setIntegerParam(pC_->motorStatusDone_, done);
        setIntegerParam(pC_->motorStatusMoving_, !done);

        epicsThreadSleep(1.);
    } while (done == 0);

    //epicsThreadSleep(3.);
    sprintf(pC_->outString_, "2 0 %i setsw 2 1 %i setsw", (axisNo_ + 1), (axisNo_ + 1));
  } else {
    //still ToDo the Home Run backward
  }
  status = pC_->writeController();
  return status;
}

Having a while-loop with an threadSleep is kind of bad coding I think, so I'm wondering if someone knows a better solution?

PS: I'm also trying to update the motor position during the while-loop (it is the "// Read the current motor position" passage). I see the correct position in the asyn communication but the .RBV value of the motor record won't update. I guess, this can only be done from the poll-function?

Best regards

Michael

Michael Sintschuk
Bundesanstalt für Materialforschung und –prüfung (BAM)
8.5 Mikro-ZfP

Unter den Eichen 87
12205 Berlin
GERMANY

P: +49 30 8062-15063 (BESSY, Adlershof)

P: +49 30 8104-4065 (BAM, Steglitz)
michael.sintschuk at bam.de<mailto:michael.sintschuk at bam.de>

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System