void plot(const char *fname="protocol.root")
{
  TFile *inFile = TFile::Open(fname);

  const int kNCh = 32;

  TTree *tree = (TTree*) inFile->Get("tree");
  TCanvas *c1 = new TCanvas("c1","c1");

  //Declaration of leaves types
  Char_t          version[3];
  Char_t          location[11];
  Char_t          comment[25];
  Int_t           iChip;
  Float_t         fAC;
  Float_t         fDC;
  Int_t           iV770;
  Int_t           iV450;
  Int_t           iV620;
  Int_t           iRef;
  Int_t           iSync;
  Int_t           iJtag;
  Int_t           iMem;
  Int_t           iClk;
  Int_t           iPlot;
  Int_t           iDFT;
  Int_t           iPed;
  Float_t         fPed[32];
  Float_t         fPed2[32];

  // Set branch addresses.
  tree->SetBranchAddress("version",version);
  tree->SetBranchAddress("location",location);
  tree->SetBranchAddress("comment",comment);
  tree->SetBranchAddress("iChip",&iChip);
  tree->SetBranchAddress("fAC",&fAC);
  tree->SetBranchAddress("fDC",&fDC);
  tree->SetBranchAddress("iV770",&iV770);
  tree->SetBranchAddress("iV450",&iV450);
  tree->SetBranchAddress("iV620",&iV620);
  tree->SetBranchAddress("iRef",&iRef);
  tree->SetBranchAddress("iSync",&iSync);
  tree->SetBranchAddress("iJtag",&iJtag);
  tree->SetBranchAddress("iMem",&iMem);
  tree->SetBranchAddress("iClk",&iClk);
  tree->SetBranchAddress("iPlot",&iPlot);
  tree->SetBranchAddress("iDFT",&iDFT);
  tree->SetBranchAddress("iPed",&iPed);
  tree->SetBranchAddress("fPed",fPed);
  tree->SetBranchAddress("fPed2",fPed2);

  Long64_t nentries = tree->GetEntries();
  cout << " nentries = " << nentries << endl;

  int nbins = 40;

  float minClk = 95;
  float maxClk = 135;

  const int kNC = 2; // nCurrenHist
  const char *curText[] = {"AC", "DC"}; 
  float curMin[kNC] = {0.3, 0.1};
  float curMax[kNC] = {0.7, 0.5};

  const int kNV = 4; // nVoltHist
  const char *voltText[] = {"V750", "V450", "V750 - V450", "V750 - V600"}; 
  float voltMin[kNV] = {750.5, 450.5, 280.5, 130.5};
  float voltMax[kNV] = {790.5, 490.5, 320.5, 170.5};

  TH1F *hV3_Clk = new TH1F("hV3_Clk", "Ring Oscillator", nbins, minClk, maxClk);
  TH1F *hV4_Clk = new TH1F("hV4_Clk", "Ring Oscillator", nbins, minClk, maxClk);

  TH1F *hV3C[kNV];
  TH1F *hV4C[kNV];

  TH1F *hV3[kNV];
  TH1F *hV4[kNV];

  char id[50], title[50];
  for (int iC=0; iC<kNC; iC++) {
    sprintf(id, "hV3%dC", iC);
    sprintf(title, "%s", curText[iC]);
    hV3C[iC] = new TH1F(id, title, nbins, curMin[iC], curMax[iC]);
    sprintf(id, "hV4%dC", iC);
    hV4C[iC] = new TH1F(id, title, nbins, curMin[iC], curMax[iC]);
  }

  for (int iV=0; iV<kNV; iV++) {
    sprintf(id, "hV3%d", iV);
    sprintf(title, "%s", voltText[iV]);
    hV3[iV] = new TH1F(id, title, nbins, voltMin[iV], voltMax[iV]);
    sprintf(id, "hV4%d", iV);
    hV4[iV] = new TH1F(id, title, nbins, voltMin[iV], voltMax[iV]);
  }

  Long64_t nbytes = 0;
  int ichan = 0;
  for (Long64_t i=0; i<nentries;i++) {
    nbytes += tree->GetEntry(i);

    TString s(version);
    if ( s.Contains("V3") ) {
      if ( (fAC>0 && fAC<1) &&
	   (fDC>0 && fDC<1) ) {
	hV3C[0]->Fill( fAC ); 
	hV3C[1]->Fill( fDC );
      }  
      if ( (iV770>100 && iV770<1000) &&
	   (iV450>100 && iV450<1000) &&
	   (iV620>100 && iV620<1000) ) {
	hV3[0]->Fill( iV770 ); 
	hV3[1]->Fill( iV450 );
	hV3[2]->Fill( iV770 - iV450);
	hV3[3]->Fill( iV770 - iV620);
      }  
      if (iClk>50) hV3_Clk->Fill( iClk ); 
    }
    else if ( s.Contains("V4") ) {
      if ( (fAC>0 && fAC<1) &&
	   (fDC>0 && fDC<1) ) {
	hV4C[0]->Fill( fAC ); 
	hV4C[1]->Fill( fDC );
      }  
      if ( (iV770>100 && iV770<1000) &&
	   (iV450>100 && iV450<1000) &&
	   (iV620>100 && iV620<1000) ) {
	hV4[0]->Fill( iV770 ); 
	hV4[1]->Fill( iV450 );
	hV4[2]->Fill( iV770 - iV450);
	hV4[3]->Fill( iV770 - iV620);
      }  
      if (iClk>50) hV4_Clk->Fill( iClk ); 
    }
  }

  c1->cd(1);
  //  c1->SetLogy(1);

  // first the clock plots
  hV3_Clk->SetLineColor(2);
  hV4_Clk->SetLineColor(4);

  gStyle->SetOptStat(0);

  hV3_Clk->Draw();
  hV4_Clk->Draw("SAME");

  char rmsinfo[20];
  TLegend* legend = new TLegend(0.6,0.6,0.9,0.9);
  legend->SetHeader("SAMPA - Clk");
  sprintf(rmsinfo,"V3 : #mu = %3.2f, #sigma = %3.2f", hV3_Clk->GetMean(), hV3_Clk->GetRMS() );
  legend->AddEntry(hV3_Clk,rmsinfo,"l");
  sprintf(rmsinfo,"V4 : #mu = %3.2f, #sigma = %3.2f", hV4_Clk->GetMean(), hV4_Clk->GetRMS() );
  legend->AddEntry(hV4_Clk,rmsinfo,"l");
  legend->Draw();

  c1->Modified();
  c1->SaveAs("V34_Clk.pdf");

  // Next the current plots
  TLegend* legendC[kNC];
  for (int iC=0; iC<kNC; iC++) {
    c1->cd(1);
    //  c1->SetLogy(1);
    hV3C[iC]->SetLineColor(2);
    hV4C[iC]->SetLineColor(4);
    
    if ( hV4C[iC]->GetMaximum() > hV4C[iC]->GetMaximum() ) {
      hV4C[iC]->Draw();
      hV3C[iC]->Draw("SAME");
    }
    else {
      hV3C[iC]->Draw();
      hV4C[iC]->Draw("SAME");
    }

    legendC[iC] = new TLegend(0.6,0.6,0.9,0.9);
    legendC[iC]->SetHeader("SAMPA - Currents");
    sprintf(rmsinfo,"V3 : #mu = %3.2f, #sigma = %3.2f", hV3C[iC]->GetMean(), hV3C[iC]->GetRMS() );
    legendC[iC]->AddEntry(hV3C[iC],rmsinfo,"l");
    sprintf(rmsinfo,"V4 : #mu = %3.2f, #sigma = %3.2f", hV4C[iC]->GetMean(), hV4C[iC]->GetRMS() );
    legendC[iC]->AddEntry(hV4C[iC],rmsinfo,"l");
    legendC[iC]->Draw();

    c1->Modified();
    sprintf(title, "V34_current%d.pdf", iC);
    c1->SaveAs(title);
  }

  // Next the voltage plots
  TLegend* legendV[kNV];
  for (int iV=0; iV<kNV; iV++) {
    c1->cd(1);
    //  c1->SetLogy(1);
    hV3[iV]->SetLineColor(2);
    hV4[iV]->SetLineColor(4);
    
    hV3[iV]->Draw();
    hV4[iV]->Draw("SAME");
    
    legendV[iV] = new TLegend(0.6,0.6,0.9,0.9);
    legendV[iV]->SetHeader("SAMPA - Bandgap");
    sprintf(rmsinfo,"V3 : #mu = %3.2f, #sigma = %3.2f", hV3[iV]->GetMean(), hV3[iV]->GetRMS() );
    legendV[iV]->AddEntry(hV3[iV],rmsinfo,"l");
    sprintf(rmsinfo,"V4 : #mu = %3.2f, #sigma = %3.2f", hV4[iV]->GetMean(), hV4[iV]->GetRMS() );
    legendV[iV]->AddEntry(hV4[iV],rmsinfo,"l");
    legendV[iV]->Draw();

    c1->Modified();
    sprintf(title, "V34_voltage%d.pdf", iV);
    c1->SaveAs(title);
  }

}