Scaler rates with 1740D

[sudb92]

• All 64 channels of 1740D fed by 4 17x2 ribbon cables from same preamp box, driven at 200-220Hz with tail pulser
• When FSUDAQ is used to inspect incoming data, the rate seen in scalers is the right value (~220Hz) for the first second or so, then drops to 95Hz and never recovers
• CoMPASS under same conditions reports steady rates (correct value 220Hz) with both waveforms as well as list mode, for 10 mins or longer (as tested)
• Verified all channels to make sure nothing wrong with input signals. Problem seems rate dependent, doesn't exist with FSUDAQ at 15Hz say. I have used latest version of FSUDAQ for testing, as on github today.
• Attached saved settings file in FSUDAQ, as well as compass .xml file. I suspect that the issue is coming from FSUDAQ also reading traces, but not sure. Doesn't crash but this behavior is odd.

Lastly, when starting/stopping runs multiple times, sometimes the online histogram viewer doesn't populate all channels. Again, this problem doesn't happen with COMPASS. All of the above with DPP-QDC and a single CAEN v1740D connected via a4818 adapter, to anasen PC with the following specs:

Ubuntu 24.04, Linux 6.8.0-85-generic

settings.xml

Digi-17121_QDC.bin.txt

[goluckyryan]

Thanks! Please check the later part of the Data::CalTriggerRate(). The TriggerRate can only be calculated by the data retrieved. The scalar rate problem could be due to the way for calculating the indexes.

The Timestamp[ch] is a circular buffer, in every CalTriggerRate() call, it needs to correctly have the correct last index to retrieve the t0, and get the last timestamp for t1, and have the total event collected since the last index.

May be worth to test 1kH, 10 kHz as well.