1. Modifications to the DRS4’s code
Claudio – PPS meeting
January 18, 2011

2. DRS4 Code Modification - Claudio
Why Is Needed ?
DAQ of two (many) DRS4’s, common trigger but running independently  event mismatch: while the second is writing out the waveforms, the first is ready to accept a trigger. And we do not know which DRS4 is “first”, so it it possible (and seen) automatic re-synchronization !
No electronics to hold the trigger until data fully saved (needed a Flip-flop set by the trigger and reset by the logical OR of all de-asserted BUSY from the DRS4’s)
The mismatch rate is related to the speed of writing out data, slow in .xml format
Jan 18, 2011
DRS4 Code Modification - Claudio

3. DRS4 Code Modification - Claudio
Change #1
To preserve, at least offline, the synchronism of the data readout, it is needed an event by event trigger information  added the trigger time into the output .xml file
Limitations:
The default times in the DRS4 code are at the second level  intrinsically DAQ limit to 1 Hz
The trigger times are software (when the DAQ receive a trigger), so they can have different delays in the two running DAQ (maybe still ok at the second level)
It affects only one DRS4, mismatching still possible
Jan 18, 2011
DRS4 Code Modification - Claudio

4. DRS4 Code Modification - Claudio
Change #2
Hard to deal with a software trigger time: we tried to read it via a scope into a separate file, but the number of triggers was larger than the number of events in the output file  the matching is even more complicated
Modified the trigger time as the ms level: it requires a deeper change (class private variables and methods and the use of different wxWidgets functions). A first version did not work since the code itself assumed trigger time changes of one second or more. New one still to be checked !
Jan 18, 2011
DRS4 Code Modification - Claudio

5. DRS4 Code Modification - Claudio
Change #3
Useful to switch the output data from .xml the a much smaller and faster format as binary file, possibility already included in the DRS4 code
Problem: it saves only the voltages relative to the waveforms of the active channels (no event serial number, no channel number, no x-axis values=times, ...)
Added all the missing information (as compressed as possible). Still to be tested ... some problem reading the binary file (SOLVED!)
Jan 18, 2011
DRS4 Code Modification - Claudio

6. DRS4 Code Modification - Claudio
Conclusions
The only way currently to prevent the event mismatch is to introduce a trigger dead time longer than the total time to write out all DRS4’s connected (how much should be established by running the code with a timer only for the save waveforms part)
A trigger time is now present for each event (for sure at the second, μs level to be tested)
We should drop the data output in the slow .xml format: either compressed formatted output (easy to implement) or binary file
Jan 18, 2011
DRS4 Code Modification - Claudio