Unable to set DC offset

[ErikHogenbirk]

We are unable to set the DC offset in kodiaq standalone mode. There is an option in the config file:

8098 DAC configuration for each channel
(1000 = negative unipolar + offset, 8000=bipolar, F000=positive
register 8098 8000

The value set here does not influence the baseline at all (tried different values). We try different options for:

baseline_mode {int}: 0 - no baselines (baseline from file), 1 - at start of each run
baseline_mode 1

including option 2 in the newer version of kodiaq, which does nothing with the baselines. Options 0 and 2 give a bipolar range (0V = 8000 ADC counts), option 1 sets the DAC offset to unipolar negative (0V = 16200 ADC counts).

Maybe I don't get the config, but does 'determine baseline' here just mean 'measure baseline' or also 'set baseline'? Is it supposed to have such behaviour?

[coderdj]

Right now there are three options for baselines:

Baseline mode 0: Set baselines from file and don't determine automatically
Baseline mode 1: Determine automatically at start of run. Use baseline file for starting values. Set determined baseline.
Baseline mode 2: Don't do anything and just write whatever is in the ini file

So in your case I think you want to set mode 2 and you should get proper behavior. Alternately you can set mode '0' and edit the files in src/slave/baselines/ to set the baselines per board. But keep in mind the file for each baseline won't be created unless you run with mode '1' once.

If this doesn't work at all then report back I guess?

I submit that this is a bit of a mess. In XENON1T mode we just run with mode '1' all the time. If you have suggestions for the other modes let me know.

FYI the determined baselines are usually in the 1000 - 1300 range.

[ErikHogenbirk]

I did some more tests and found the same results as before, but only for the V1730. So, in summary:

V1730, mode 0: baseline at 8200 no matter what the settings (including baseline file)
V1730, mode 1: baseline at 16000 no matter what the settings
V1730, mode 2: baseline at 8200 no matter what the settings

V1724, mode 0: baseline determined by baseline file
V1724, mode 1: baseline at 16000 no matter what the settings
V1724, mode 2: baseline determined by register 8098.

How can it be that our digitizer seems incompatible with mode 2 and mode 0? I already checked that the registers map is OK, i.e. register 8098 is still 8098 for the V1730. Do you have any suggestions?

PS I found the determined baselines of the V1730 digitizer in the 1000-1200 range, but for the V1724 they were around 4000.

[coderdj]

Actually that makes no sense. If it was mode 1 that was incompatible then I would assume it's because there are so many other registers involved in baseline determination that one was just different. But mode 0 and 2 make no sense. The only register involved in this case is 1n98 (mode 0) and 8098 (mode 2).

Are you using the exact same .ini file for both digitizers? As in with no other registers changed? If so I have no idea. Maybe you stumbled onto another firmware bug.

[ErikHogenbirk]

Yes, except for a few registers we changed because they were different for the V1730 than the V1724. I just tried again with exactly the same settings as for the V1724, but it's still the same. I think I'll contact CAEN about this and see if it can be fixed.