We did a further investigation of this problem:
We figured out that this issue seems to be related to the kernel.
We tested it now on two machines with Ubuntu 14.04.2 LTS (kernel 3.16.0-41), one with RHEL 6.6 (kernel 2.6.32) , one with Fedora 20 (kernel 3.18.7) and one with Mac OSX. We see this issue with the Ubuntu and the fedroa machines.Both have a kernel above 3.0 while RHEL has a kernel of 2.6
We can repoduce the problem on all input channels as a trigger.
I will try to find out what could be the cause of it.
We are working with the DRS 4 V5 version and we investigated an issue with the trigger at rates below ~120 Hz.
As long as we have a trigger rate of more than 125 Hz. everything seems to work fine and we are recording more or less all events.
As soon as we go lower in input trigger rate to 100Hz, we see a drop in trigger rates to approx 15 - 20 Hz.
When we use the new firmware we can see that the busy signal is 0 for much longer times than usual up to .5 seconds.
We made a plot of input trigger rate vs trigger rate of drs: https://plot.ly/~simon.corrodi/316
In the oscilloscope plots one can see the the trigger in in yellow and the trig out from drs board in blue.
Do you have any idea what could be the reason?