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<== Date ==> <== Thread ==>

Subject: asynPortDriver and read/write access to record fields
From: Dr. Bastian Löher <b.loeher@gsi.de>
To: <tech-talk@aps.anl.gov>
Date: Tue, 18 Sep 2018 21:44:24 +0200
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


Replies:
RE: asynPortDriver and read/write access to record fields Mark Rivers

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