source: fact/tools/rootmacros/DrsCalibration.C

#include "DrsCalibration.h"

#include <iostream>
using namespace std;

float getValue( int slice, int pixel,
    vector<float> &drs_basemean,
    vector<float> &drs_gainmean,
    vector<float> &drs_triggeroffsetmean,
    unsigned int    RegionOfInterest,
    vector<int16_t> AllPixelDataVector,
    vector<int16_t> StartCellVector
){
    const float dconv = 2000/4096.0;

    float vraw, vcal;

    unsigned int pixel_pt;
    unsigned int slice_pt;
    unsigned int cal_pt;
    unsigned int drs_cal_offset;

    // printf("pixel = %d, slice = %d\n", slice, pixel);

    pixel_pt = pixel * RegionOfInterest;
    slice_pt = pixel_pt + slice;
    drs_cal_offset = ( slice + StartCellVector[ pixel ] )%RegionOfInterest;
    cal_pt    = pixel_pt + drs_cal_offset;

    vraw = AllPixelDataVector[ slice_pt ] * dconv;
    vcal = ( vraw - drs_basemean[ cal_pt ] - drs_triggeroffsetmean[ slice_pt ] ) / drs_gainmean[ cal_pt ]*1907.35;

    return( vcal );
}



// FACT raw data is stored in fits files in large vector<int16_t>. these
// containt the data of the full camera for a single event.
// in order to work with this data, one needs to extract the part, which
// belongs to the current pixel and apply a DRS calibration, based on a dedicated
// DRS calibration file.
//
// TODO: The calibration Data as well as the Data and StartCell vectors are a bit
// massive to give this function as parameters.
// better to have these vectors somehow bundled in classes like:
// RawData - class and
// DrsCalibration - class
// those classes would be the result of
// openDataFits() and
// openCalibFits()
//
size_t applyDrsCalibration(
        vector<float> &destination,
        int pixel,
        int LeaveOutLeft,
        int LeaveOutRight,
        vector<float> &drs_basemean,
        vector<float> &drs_gainmean,
        vector<float> &drs_triggeroffsetmean,
        unsigned int RegionOfInterest,
        vector<int16_t> AllPixelDataVector,
        vector<int16_t> StartCellVector,
        int verbosityLevel
){
    // In order to minimize mem free and alloc actions
    // the destination vector is only resized, if it is way too big
    // or too small
    size_t DestinationLength = RegionOfInterest-LeaveOutRight-LeaveOutLeft;
    if ( destination.size() != DestinationLength){
        destination.resize( DestinationLength );
    }

    //  We do not entirely know how the calibration constants, which are saved in a filename.drs.fits file
    // were calculated, so it is not fully clear how they should be applied to the raw data for calibration.
    // apparently the calibration constants were transformed to the unit mV, which means we have to do the same to
    // the raw data prior to apply the calibration
    //
    // on the FAD board, there is a 12bit ADC, with a 2.0V range, so the factor between ADC units and mV is
    // ADC2mV = 2000/4096. = 0.48828125 (numerically exact)
    //
    // from the schematic of the FAD we learned, that the voltage at the ADC
    // should be 1907.35 mV when the calibration DAC is set to 50000.
    //
    // One would further assume that the calibration constants are calculated like this:

    // The DRS Offset of each bin in each channel is the mean value in this very bin,
    // obtained from so called DRS pedestal data
    // Its value is about -1820 ADC units or -910mV

    // In order to obtain the DRS Gain of each bin of each channel
    // again data is takes, with the calibration DAC set to 50000
    // This is called DRS calibration data.
    // We assume the DRS Offset is already subtracted from the DRS calibration data
    // so the typical value is assumed to be ~3600 ADC units oder ~1800mV
    // As mentioned before, the value *should* be 1907.35 mV
    // So one might assume that the Gain is a number, which actually converts ~3600 ADC units into 1907.35mV for each bin of each channel.
    // So that the calibration procedure looks like this
    // TrueValue = (RawValue - Offset) * Gain
    // The numerical value of Gain would differ slightly from the theoretical value of 2000/4096.
    // But this is apparently not the case.
    // The Gain, as it is stored in the DRS calibration file of FACT++ has numerical values
    // around +1800.
    // So it seems one should calibrate like this:
    // TrueValue = (RawValue - Offset) / Gain * 1907.35

    // When these calibrations are done, one ends up with a quite nice calibrated voltage.
    // But it turns out that, if one returns the first measurement, and calculates the mean voltages
    // in each bin of the now *logical* DRS pipeline, the mean voltage is not zero, but slightly varies
    // So one can store these systematical deviations from zero in the logical pipeline as well, and subtract them.
    // The remaining question is, when to subtract them.
    // I assume, in the process of measuring this third calibration constant, the first two
    // calibrations are already applied to the raw data.

    // So the calculation of the calibrated volatage from some raw voltage works like this:
    // assume the raw voltage is the s'th sample in channel c. While the Trigger made the DRS stopp in its t'th cell.
    // note, that the DRS pipeline is always 1024 bins long. This is constant of the DRS4 chip.

    // TrueValue[c][s] = ( RawValue[c][s] - Offset[c][ (c+t)%1024 ] ) / Gain[c][ (c+t)%1024 ] * 1907.35 - TriggerOffset[c][s]

    const float dconv = 2000/4096.0;
    float vraw;

    if ( RegionOfInterest != AllPixelDataVector.size()/1440 ){
        if (verbosityLevel > 0){
            cout << "RegionOfInterest != AllPixelDataVector.size()/1440" << endl;
            cout << "RegionOfInterest: " << RegionOfInterest << endl;
            cout << "AllPixelDataVector.size(): " << AllPixelDataVector.size() << endl;
            cout << "aborting" << endl;
        }
        return 0;
    }

    // the vector drs_triggeroffsetmean is not 1440 * 1024 entries long
    // but has hopefully the length 1440 * RegionOfInterest (or longer)
    if ( drs_triggeroffsetmean.size() < 1440*RegionOfInterest ){
        if (verbosityLevel > 0){
            cout << "Error: drs_triggeroffsetmean.size() < 1440*RegionOfInterest" << endl;
            cout << "drs_triggeroffsetmean.size():" << drs_triggeroffsetmean.size() << endl;
            cout << "RegionOfInterest" << RegionOfInterest << endl;
            cout << "aborting" << endl;
        }
        return 0;
    }

    int DataPos, OffsetPos, TriggerOffsetPos;

    for ( unsigned int sl = LeaveOutLeft; sl < RegionOfInterest-LeaveOutRight ; sl++){

        DataPos = pixel * RegionOfInterest + sl;
        // Offset and Gain vector *should look the same
        OffsetPos = pixel * drs_basemean.size()/1440 + (sl + StartCellVector[pixel])%(drs_basemean.size()/1440);

        TriggerOffsetPos = pixel * drs_triggeroffsetmean.size()/1440 + sl;

        vraw = AllPixelDataVector[ DataPos ] * dconv;
        vraw -= drs_basemean[ OffsetPos ];
        vraw -= drs_triggeroffsetmean[ TriggerOffsetPos ];
        vraw /= drs_gainmean[ OffsetPos ];
        vraw *= 1907.35;

//              slice_pt = pixel_pt + sl;
//              drs_cal_offset = ( sl + StartCellVector[ pixel ] ) % RegionOfInterest;
//              cal_pt    = pixel_pt + drs_cal_offset;
//              vraw = AllPixelDataVector[ slice_pt ] * dconv;
//              vcal = ( vraw - drs_basemean[ cal_pt ] - drs_triggeroffsetmean[ slice_pt ] ) / drs_gainmean[ cal_pt ]*1907.35;
//              destination.push_back(vcal);

        destination[sl-LeaveOutLeft] = vraw;
    }

    return destination.size();
}