Experimental Physics and
Industrial Control System

Rok Šabjan <[email protected]> · Fri, 29 Feb 2008 00:12:02 +0800

Hi Heinrich,
I remember this problem as we had it in 2004. I remember that we were
not able to solve it, but it did not occur if we used a command-line
client that wrapped the CDEV library. At that time I did not care
about that, but it may help if you want to track down the problem.
Regards,
Rok

On 28.2.2008, at 23:51, Heinrich du Toit wrote:
Hi
This is weird and I'm not really sure how to track it down.
I have an embedded ARM board. I've compiled EPICS onto that.
I run vlinac (just to get something ) on my host PC (x86)
Then I take an ai variable. (in other words a floating point thing)
If I say from the ARM board caput  pvname value
Then the correct value gets into the pv on my host pc.
But.. the wrong value gets back via channel access.
if I caget the value I get the wrong answer.
It seems that the network byte order is done wrongly maybe.. I'm not
sure.

If I put 1.0

and then get again I get: 5.29981e-315
Which is almost like the wrong network byte order but not exactly it
seems.

It could be that somewhere along the lines something thinks double
is 6 bytes only (rather than 8) and then also swaps the byte order.
Maybe there is an htons or something missing somewhere in the code?
But how this is possible baffles me. :/
I've written a small program to test the structure and layout off
"double" on both my PC and the ARM. it seems identical to me.
If anybody has any idea how I can "check" this or try and find the
problem it would be help full.

I am aware that the problem is not necessarily in epics but could be
in the compiler options or something like that.

thanks
-Heinrich

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System