how to work properly with device when you need query every 5 seconds

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kas1e

Posted on: 2021/1/1 7:40 #1

Home away from home

The question comes up after finding that when you need one time in a 5-second query something from a serial device, then if you open-close device for every query, then you have 100% CPU load hit on that time. I.e there is init code:


BOOL initX5000serial(struct DockyData *dd)

{

    BOOL res = FALSE;

    int8 err = 0;



    dd->port = IExec->AllocSysObject(ASOT_PORT, NULL);

    if(dd->port)

    {

        dd->req = IExec->AllocSysObjectTags(ASOT_IOREQUEST, ASOIOR_Size,sizeof(struct IOExtSer),

                                            ASOIOR_ReplyPort,dd->port, TAG_DONE);

        if(dd->req)

        {

            

            if(IExec->OpenDevice("serial.device", 1, (struct IORequest*)dd->req, 0) != -1)

            {

                // Set parameters to address MCU 

                dd->req->IOSer.io_Command = SDCMD_SETPARAMS;

                dd->req->io_Baud      = 38400; // 38400 Baud

                dd->req->io_ReadLen   = 8;     // 8 bit data

                dd->req->io_WriteLen  = 8;     // 8 bit data

                dd->req->io_StopBits  = 1;     // 1 Stop bit

                dd->req->io_SerFlags &= ~SERF_PARTY_ON; // No Parity

                dd->req->io_SerFlags |= SERF_XDISABLED; // No Flow Control

                err = IExec->DoIO( (struct IORequest*)dd->req );

                if(err == IOERR_SUCCESS)

                {

                    res = TRUE;

                }

            }

        }

    }

    return(res);

}

There is de-init code:


void closeX5000serial(struct DockyData *dd)

{

    if(dd->dev_open) { IExec->CloseDevice( (struct IORequest*)dd->req ); dd->dev_open = FALSE; }

    if(dd->req) { IExec->FreeSysObject(ASOT_IOREQUEST, dd->req); dd->req = NULL; }

    if(dd->port) { IExec->FreeSysObject(ASOT_PORT, dd->port); dd->port = NULL; }

}

Now if we do something like:


dd->dev_open = initX5000serial(dd);

  if(dd->dev_open)

  {

   QueryTemp(dd);

   QueryVoltFan(dd);

  }

We then hit 100% CPU loading every time we query our stuff.

If I remember right, it is correct to open/close the device for every query, right? And it should be not opened all the time?

Any advice is welcome, thanks!

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ncafferkey

Re: how to work properly with device when you need query every 5 seconds

Posted on: 2021/1/2 2:58 #2

Just popping in

@kas1e

Whether you should leave a device open or not depends on the use case. Could other programs need to access it in between your accesses? Will your having the device open block other accesses? (I'm too lazy to read the serial.device AutoDoc right now

)

Again, I'm not sure of the use case. My guess is you have custom monitoring hardware attached to one of the X5000's serial headers. Or is it standard? Ideally, there would be a hardware monitor API that would share out this information to multiple listeners. Then it wouldn't matter much if the "API" blocked other direct access to the serial device.

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