Experimental Physics and
Industrial Control System

> When using MEDM to display the waveform using the Cartesian plot, one must (so I understand) adjust the 'LOPR', 'HOPR', and 'NELM' fields of the record for the time X axis.

I believe that NELM cannot be changed after iocInit.  It would need to be large enough for the largest waveform you will display.

You can change HOPR and LOPR for the X and Y waveform records to change the displayed range in medm.  However, medm does not automatically rescale the plot when you change HOPR and LOPR, so you must close and re-open the plot when you change those. 

Mark


-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Dr. Bastian Löher
Sent: Tuesday, September 18, 2018 2:44 PM
To: [email protected]
Subject: asynPortDriver and read/write access to record fields

Hi,

I'm in the process of implementing an asynPortDriver based driver for a USB scope (Picotech 2000 series). The driver is based on the testAsynPortDriver example.

Since a real device is connected the driver produces waveforms, where the length and axis ranges depend on the user settings (i.e. capture time, sampling frequency and so on).

---

When using MEDM to display the waveform using the Cartesian plot, one must (so I understand) adjust the 'LOPR', 'HOPR', and 'NELM' fields of the record for the time X axis.

When taking the axis range in MEDM from the channel, then the waveform will be clipped (when NELM is too small), or it will only occupy part of the display (when NELM is too large).

I also tested auto-scale of the axis, but in that case also the axis labels are never changed.

---

What is the standard procedure here? Should I use something else than MEDM? Or is it possible to get to work by changing my code/record database?

---

I've seen an old post using intermediate 'longout' records, but they didn't seem to work as intended.
(https://epics.anl.gov/tech-talk/2015/msg00289.php)


Thanks

Bastian

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Re: asynPortDriver and read/write access to record fields Loeher, Bastian Dr.

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