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

Subject: Re: VXI11 - GPIB
From: Zenon Szalata <zms@slac.stanford.edu>
To: Mark Rivers <rivers@cars.uchicago.edu>
Cc: "tech-talk@aps.anl.gov" <tech-talk@aps.anl.gov>
Date: Fri, 11 Oct 2013 15:59:42 -0700
Hi Mark and Matt,
First Mark's questions:
With read buffer length of  greater than 32, writeRead fails with status 1,
which I think means that it is timing out on the read part.

Trace back gives:
2013/10/11 13:40:20.234 L0x 12 vxiWrite

1e 00 11 00 04 00 12 00 1a
epics> drvKS3988::_writeRead: stat=1,l=1,nw=1,bln=4,nbi=0

Stat in the print statement in my driver is the return code and nbi is the number of bytes returned, both from the asynOctetSyncIO->wrteRead() function. So, it failed to read.

On the other hand, with read buffer length of 32 or less:
trace back gives:
2013/10/11 13:08:48.636 L0x 12 vxiWrite

1e 00 11 00 04 00 12 00 1a
2013/10/11 13:08:48.638 L0x 12 vxiRead

0c
drvKS3988::_writeRead: stat=0,l=1,nw=1,bln=4,nbi=1

Matt,
I have not defined either the input nor output EOS characters. The code worked with small read buffer size. It stopped working when I increased the buffer size and it did not occur to me that this might be needed. In each case, the device replies with one byte of data.

The hardware set up is:
Agilent Ethernet - GPIB <--> Kinetic Systems GPIB CAMAC crate controller.
I wonder if I could use IP Port driver instead of VXI11 driver?
I will look at the document for the KS3988 to see how it terminated its reply data; it might help understand what is going on.
Thank you both,
Zen

On 10/11/13 13:58, Mark Rivers wrote:
Something does not seem right here, I don't understand why it is failing if nbt > 32.

Unfortunately I have no experience with VXI11, and I don't have any VXI11 devices to test with.  Hopefully someone else on tech-talk can help you with this.

When the writeRead fails, what is the error return?

What do you see if you set asynTraceMask=255 in the underlying VXI11 port (L0x)?

Mark


-----Original Message-----
From: Zenon Szalata [mailto:zms@slac.stanford.edu]
Sent: Friday, October 11, 2013 3:34 PM
To: Mark Rivers; tech-talk@aps.anl.gov
Subject: VXI11 - GPIB

Hi Mark,
I have written a device driver for a GPIB device that is using VXI11
protocol.
The device driver is sub-classed from the asynPortDriver class.
In the st.cmd file I configure the VXI11 object as follows:
vxi11Configure( "L0x","$(ETHER)",0,0.0,"gpib0",0,0)

Then in the constructor I connect:

stat=pasynOctetSyncIO->connect( _ioPort,_addr,&_apvt,0);

finally in IO routine I call:

stat=pasynOctetSyncIO->writeRead(
_apvt,pcs,ncb,_buf,nbt,1,(size_t*)nio,&nbi,&eom);

_buf is defined as char _buf[2048]

I have discovered by trial and error that the writeRead succeeds for nbt
<= 32 and fails otherwise.
I do not understand this.  I think that nbt is supposed to be the size
of the read buffer (in my case _buf) simply telling the routine, which
ultimately does the device IO, to put up to nbt bytes of data into the
read buffer.  Now, it happens that in my test case the device returns
only one byte of data, that is the status byte. So, why should it fail
when I give the writeRead a ridiculously large buffer to read into?

Then what if I poke the device and it chooses to reply by sending 1024
bytes of data?  Do I need to worry about that and issue the writeRead
number of times with 32 byte long read buffer until all bytes of data
are read in?  Since I don't know before hand how much data will be
returned, it is not obvious to me how this could be done efficiently.
Thanks Mark,
Zen


Replies:
RE: VXI11 - GPIB Mark Rivers
References:
VXI11 - GPIB Zenon Szalata
RE: VXI11 - GPIB Mark Rivers

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