diff --git a/.gitignore b/.gitignore
index 26af173..cc99b4e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,6 +1,4 @@
 
-/build
-
 eatraw
 eatdev
 
@@ -8,11 +6,14 @@ nohup.out
 
 .DS_Store
 
-*.so
-
 raw_eater.cpp
 raw_meat.cpp
 
 cyt/*.cpp
+/build
 
+*.log
+*.so
 *.o
+*.csv
+*.parquet
diff --git a/cyt/raw_eater.pxd b/cyt/raw_eater.pxd
index a93e758..65f1f33 100644
--- a/cyt/raw_eater.pxd
+++ b/cyt/raw_eater.pxd
@@ -14,14 +14,18 @@ from libcpp cimport bool
 #
 # for how to overload the constructor see
 # https://cython.readthedocs.io/en/latest/src/userguide/wrapping_CPlusPlus.html
+# and propagating exceptions from C++ to Python
+# http://docs.cython.org/en/latest/src/userguide/wrapping_CPlusPlus.html#exceptions
 
 cdef extern from "../lib/raweat.hpp":
     cdef cppclass raw_eater:
         # constructor(s)
-        raw_eater() except+
+        raw_eater() except +
         raw_eater(string) except +
         # set new file for decoding
         void set_file(string)
+        # perform conversion (pass any C++ exceptions to Python)
+        void setup_and_conversion() except +
         # get validity of data format
         bool get_valid()
         # get channel name and unit
diff --git a/cyt/raw_eater.pyx b/cyt/raw_eater.pyx
index 7ca4b52..c079033 100644
--- a/cyt/raw_eater.pyx
+++ b/cyt/raw_eater.pyx
@@ -30,6 +30,9 @@ cdef class raweater:
       raise ValueError("'" + str(rawfile) + "' does not exist")
     self.rawit.set_file(rawfile)
 
+  def do_conversion(self):
+      self.rawit.setup_and_conversion()
+
   def validity(self):
     return self.rawit.get_valid()
 
diff --git a/cyt/raw_meat.pxd b/cyt/raw_meat.pxd
index 56e12c5..a5d493c 100644
--- a/cyt/raw_meat.pxd
+++ b/cyt/raw_meat.pxd
@@ -23,8 +23,8 @@ cdef extern from "../lib/rawmerge.hpp":
         vector[double] get_data()
         # dump all data to .csv
         void write_table(const char*,char)
-        # add channel and try to merge it
-        bool add_channel(string)
+        # add channel and try to merge it (pass C++ exceptions to Python)
+        bool add_channel(string) except +
         # get total number of (added) channels
         int get_num_channels()
         # get list of channel names
diff --git a/lib/raweat.hpp b/lib/raweat.hpp
index dce867b..42637d4 100644
--- a/lib/raweat.hpp
+++ b/lib/raweat.hpp
@@ -80,7 +80,7 @@ public:
   raw_eater(std::string rawfile, bool showlog = false) : rawfile_(rawfile)
   {
     // trigger setup and conversion
-    if ( ! rawfile.empty() ) this->setup_and_conversion(showlog);
+    //if ( ! rawfile.empty() ) this->setup_and_conversion(showlog);
   }
 
   raw_eater()
@@ -88,6 +88,12 @@ public:
 
   }
 
+  // destructor
+  ~raw_eater()
+  {
+
+  }
+
   // provide/set new raw file
   void set_file(std::string rawfile, bool showlog = false)
   {
@@ -100,11 +106,11 @@ public:
     datmes_.clear();
 
     // do setup and conversion
-    setup_and_conversion(showlog);
+    //setup_and_conversion(showlog);
   }
 
   // set up and conversion
-  void setup_and_conversion(bool showlog)
+  void setup_and_conversion(bool showlog = false)
   {
     // make sure 'raw_file' is already set
     assert ( !rawfile_.empty() );
@@ -123,10 +129,8 @@ public:
 
     if ( showlog )
     {
-      // show raw data
+      // show raw data and display predefined markers
       this->show_buffer();
-
-      // display predefined markers
       this->show_markers();
     }
 
@@ -150,12 +154,6 @@ public:
     }
   }
 
-  // destructor
-  ~raw_eater()
-  {
-
-  }
-
   // display buffer/data properties
   void show_buffer(int numel = 32)
   {
@@ -239,10 +237,16 @@ public:
     unsigned long int totalmarksize = 0;
     for (std::pair<std::string,std::vector<unsigned char>> mrk : markers_ )
     {
-      //assert ( datasec_[mrk.first].size() > 0 && "marker segment of length zero" );
       if ( datasec_[mrk.first].size() == 0 )
       {
-        std::cout<<"warning: "<<mrk.first<<" not found in buffer\n";
+        std::string errmess = mrk.first + std::string(" not found in buffer");
+        // std::cerr<<errmess;
+        try {
+          throw std::runtime_error(errmess);
+        } catch( const std::exception& e ) {
+          throw;
+	        //std::cout<<e.what()<<"\n";
+        }
       }
       totalmarksize += datasec_[mrk.first].size();
     }
@@ -250,7 +254,6 @@ public:
     // std::cout<<"\n";
 
     // check validity of format
-    // assert ( totalmarksize > 0 && "didn't find any predefined marker => probably not a valid .raw-file" );
     valid_ = ( totalmarksize < 100 ) ? false : true;
   }
 
@@ -389,7 +392,6 @@ public:
     }
     else
     {
-
       // switch for datatypes
       switch ( dattype )
       {
@@ -414,9 +416,9 @@ public:
           convert_data_as_type<unsigned long int>(datbuf,factor,offset);
           break;
         case 6 :
-          std::cout<<"warning: 'signed long int' datatype with experimental support\n";
           // assert ( sizeof(signed long int)*8 == typesize );
           // convert_data_as_type<signed long int>(datbuf,factor,offset);
+          // throw std::runtime_error("warning: 'signed long int' datatype with experimental support");
           assert ( sizeof(int)*8 == typesize );
           convert_data_as_type<int>(datbuf,factor,offset);
           break;
@@ -429,13 +431,13 @@ public:
           convert_data_as_type<double>(datbuf,factor,offset);
           break;
         case 9 :
-          std::cerr<<"'imc Devices Transitional Recording' datatype not supported\n";
+          throw std::runtime_error("'imc Devices Transitional Recording' datatype not supported");
           break;
         case 10 :
-          std::cerr<<"'Timestamp Ascii' datatype not supported\n";
+          throw std::runtime_error("'Timestamp Ascii' datatype not supported");
           break;
         case 11 :
-          std::cout<<"warning: '2-Byte-Word digital' datatype with experimental support\n";
+          // throw std::runtime_error("warning: '2-Byte-Word digital' datatype with experimental support");
           assert ( sizeof(short int)*8 == typesize );
           convert_data_as_type<short int>(datbuf,factor,offset);
           break;
diff --git a/lib/rawmerge.hpp b/lib/rawmerge.hpp
index 42bfe9d..3e77e48 100644
--- a/lib/rawmerge.hpp
+++ b/lib/rawmerge.hpp
@@ -83,13 +83,19 @@ public:
   {
     // set raw file and perform conversion
     this->set_file(rawfile,showlog);
+    // try {
+    this->setup_and_conversion();
+    // } catch (const std::exception& e) {
+    //   // throw;
+    //   std::cout<<e.what();
+    // }
 
     // show channel name, unit, timestep, time unit, etc.
     if ( showlog && this->get_valid() )
     {
-      std::cout<<this->get_name()<<" ["<<this->get_unit()<<"]"<<"\n";
       std::cout<<"Time ["<<this->get_temp_unit()<<"]"<<"\n";
       for ( unsigned long int i = 0; i < 5; i++ ) std::cout<<this->get_time()[i]<<"\n";
+      std::cout<<this->get_name()<<" ["<<this->get_unit()<<"]"<<"\n";
       for ( unsigned long int i = 0; i < 5; i++ ) std::cout<<this->get_data()[i]<<"\n";
       std::cout<<"lenght of channel "<<this->get_time().size()<<"\n";
       std::cout<<"\n";
@@ -126,12 +132,9 @@ public:
         std::vector<double> td = this->get_data();
 
         // compare start/end of timeseries (define tolerance)
-        double deltat = 7*fmax(this->get_dt(),this->dt_);
-        if ( ( this->timeseries_[0]     - ts[0]     < deltat  )
-          && ( this->timeseries_.back() - ts.back() < deltat ) )
-        // double tol = 0.001;
-        // if ( ( (this->timeseries_[0]-ts[0])/ts[0] < tol )
-        //   && ( (this->timeseries_.back()-ts.back())/ts.back() < tol ) )
+        double deltat = 9*fmax(this->get_dt(),this->dt_);
+        if ( ( fabs( this->timeseries_[0]     - ts[0] )     < deltat  )
+          && ( fabs( this->timeseries_.back() - ts.back() ) < deltat ) )
         {
           // resulting new time series
           std::vector<double> newts;
@@ -155,9 +158,14 @@ public:
         else
         {
           // refuse to merge due to inconsistent start of timeseries
-          std::cerr<<"rawmerge: add_channel '"<<rawfile
-                   <<"' : inconsistent start of time series, i.e. "
-                   <<timeseries_[0]<<" vs. "<<ts[0]<<"\n";
+          std::string errmess = std::string("rawmerge: add_channel '") + rawfile
+                              + std::string("' : inconsistent start of time series, i.e. ")
+                              + std::to_string(timeseries_[0]) + std::string(" vs. ")
+                              + std::to_string(ts[0])
+                              + std::string("( timesteps: ") + std::to_string(this->get_dt())
+                              + std::string(" and ") + std::to_string(this->dt_) + std::string(")");
+          // std::cerr<<errmess<<"\n";
+          throw std::runtime_error(errmess);
 
           return false;
         }
@@ -165,9 +173,12 @@ public:
       else
       {
         // refuse to merge due to different temporal units
-        std::cerr<<"rawmerge: add_channel '"<<rawfile
-                 <<"' : inconsistent time units: '"
-                 <<this->get_temp_unit()<<"' versus '"<<this->temp_unit_<<"'\n";
+        std::string errmess = std::string("rawmerge: add_channel '") + rawfile
+                            + std::string("' : inconsistent time units: ', i.e. '")
+                            + this->get_temp_unit() + std::string("' vs. '")
+                            + this->temp_unit_ + std::string("'");
+        // std::cerr<<errmess<<"\n";
+        throw std::runtime_error(errmess);
 
         return false;
       }
@@ -175,7 +186,10 @@ public:
     else
     {
       // provided file does not feature a valid .raw format
-      std::cerr<<"rawmerge: add_channel '"<<rawfile<<"' : invalid .raw file\n";
+      std::string errmess = std::string("rawmerge: add_channel '") + rawfile
+                          + std::string("' : invalid .raw file");
+      // std::cerr<<errmess<<"\n";
+      throw std::runtime_error(errmess);
 
       return false;
     }
diff --git a/makefile b/makefile
index 9a43f8f..c33bea0 100644
--- a/makefile
+++ b/makefile
@@ -15,13 +15,14 @@ EXE = eatraw
 
 # compiler and its options
 CCC = g++ -std=c++11
-OPT = -O3 -Wall -mavx -mno-tbm -mf16c -mno-f16c
+#OPT = -O3 -Wall -mavx -mno-tbm -mf16c -mno-f16c
+OPT = -O3 -Wall -Werror
 
 #-----------------------------------------------------------------------------#
 # C++
 
 # build executable
-$(EXE) : $(SRC)main.cpp $(LIB)raweat.hpp $(LIB)hexshow.hpp $(LIB)rawmerge.hpp
+$(EXE) : $(SRC)main.cpp $(LIB)raweat.hpp $(LIB)hexshow.hpp $(LIB)rawmerge.hpp output
 	$(CCC) $(OPT) $< -o $@
 
 # development version
@@ -37,6 +38,7 @@ clean :
 	rm -f $(EXE)
 	rm -f eatall
 	rm -f eatdev
+	rm -rf output/
 
 # check existence of name of executable globally
 chexe:=$(shell command -v $(EXE))
@@ -59,7 +61,8 @@ uninstall :
 
 # build python module
 py : $(CYT)setup_raw_eater.py $(CYT)raw_eater.pyx $(CYT)raw_eater.pxd $(LIB)raweat.hpp \
-     $(CYT)setup_raw_meat.py $(CYT)raw_meat.pyx $(CYT)raw_meat.pxd $(LIB)rawmerge.hpp
+     $(CYT)setup_raw_meat.py $(CYT)raw_meat.pyx $(CYT)raw_meat.pxd $(LIB)rawmerge.hpp \
+		 output
 	python3 $(CYT)setup_raw_eater.py build_ext --inplace
 	python3 $(CYT)setup_raw_meat.py build_ext --inplace
 	cp raw_eater.cpython-*.so pyt/
@@ -80,5 +83,10 @@ py-clean :
 	rm -f $(CYT)raw_meat.cpp
 	rm -rf build/
 	rm -f *.txt
+	rm -rf output/
+
+# prepare directory for test output
+output :
+	mkdir -pv output/
 
 #-----------------------------------------------------------------------------#
diff --git a/pyt/example.py b/pyt/example.py
index efb06ec..aa43af3 100644
--- a/pyt/example.py
+++ b/pyt/example.py
@@ -5,65 +5,23 @@ import raw_eater
 import raw_meat
 import pyarrow as pa
 import pyarrow.parquet as pq
+import glob
+from pathlib import Path
 
-rawlist1 = [
-            "smp/Rangerover_Evoque_F-RR534_2019-05-07/BrakePedalActiveQF_HS.raw",
-            "smp/Rangerover_Evoque_F-RR534_2019-05-07/BrakePressure_HS.raw",
-            "smp/Rangerover_Evoque_F-RR534_2019-05-07/EngineSpeed_HS.raw",
-            "smp/Rangerover_Evoque_F-RR534_2019-05-07/pressure_FL.raw",
-            "smp/Rangerover_Evoque_F-RR534_2019-05-07/pressure_RL.raw",
-            "smp/Rangerover_Evoque_F-RR534_2019-05-07/pressure_Vacuum.raw",
-            "smp/VehicleSpeed_HS.raw",
-            "smp/Rangerover_Evoque_F-RR534_2019-05-07/ABS_A_Port1.raw",
-            "./pyt/example.py",
-            "smp/Rangerover_Evoque_F-RR534_2019-05-07/LateralAcceleration_HS.raw",
-            "smp/Rangerover_Evoque_F-RR534_2019-05-07/Temp_Disc_FR.raw"
-          ]
+fileobj1 = Path("smp/Rangerover_Evoque_F-RR534_2019-05-07/").rglob("*.raw")
+rawlist1 = [str(fl) for fl in fileobj1]
 
-rawlist2 = [
-"smp/Mercedes_E-Klasse-2019-08-08/ACC_lat.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/ACC_long.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Flex_AccelPdlPosn.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Flex_AirTemp_Outsd_IC.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Flex_AirTemp_Outsd.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Flex_BrkPdl_Stat.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Flex_BrkTrq_D_V2.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Flex_BrkTrq_R.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Flex_BrkTrq_V2.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Flex_EngLoad_OBD.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Flex_EngRPM.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Flex_Odo.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Flex_PkBrk_Stat.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Flex_StWhl_Angl.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Flex_StWhl_AnglSpd.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Flex_TC_liquidFuelCons1.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Flex_VehSpd_Disp.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Flex_WhlRPM_FL.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Flex_WhlRPM_FR.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Flex_WhlRPM_RL.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Flex_WhlRPM_RR.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/GPS.height.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/GPS.speed.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/GPS.time.sec.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Pressure_FL.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Pressure_PC.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Pressure_RR.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Pressure_SC.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/setup_id.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Temp_Disc_FL.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Temp_Disc_FR.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Temp_Disc_RL.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Temp_Disc_RR.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Temp_Fluid_FL.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Temp_Fluid_RL.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Travel_Piston.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/Vacuum_Booster.raw",
-"smp/Mercedes_E-Klasse-2019-08-08/vehicle_id.raw"
-]
+fileobj2 = Path("smp/Mercedes_E-Klasse-2019-08-08/").rglob("*.raw")
+rawlist2 = [str(fl) for fl in fileobj2]
 
-rawlist = rawlist2
+rawlist = rawlist1 #[rawlist1[0],rawlist1[4],rawlist2[0],rawlist2[6]]
+for fil in rawlist2 :
+    rawlist.append(fil)
+rawlist.append("smp/pressure_Vacuum.asc")
 
 print("")
+print(rawlist)
+print()
 
 #-----------------------------------------------------------------------------#
 
@@ -80,8 +38,12 @@ for rf in rawlist :
     # eatraw = raw_eater.raweater(rf.encode())
     # eatraw = raw_meat.rawmerger(rf.encode())
 
-    # use global instance of "raw_eater"
+    # use global instance of "raw_eater" to set file and perform decoding
     eatraw.set_file(rf.encode())
+    try :
+        eatraw.do_conversion()
+    except RuntimeError as e :
+        print("conversion failed: " + str(e))
 
     # check validity of file format
     if eatraw.validity() :
@@ -106,7 +68,7 @@ for rf in rawlist :
         outname = rf.split('/')[-1].replace('raw','csv')
 
         print("write output to : " + outname)
-        eatraw.write_table((outname).encode(),ord(' '))
+        eatraw.write_table(("output/"+outname).encode(),ord(' '))
 
     else :
 
@@ -124,17 +86,17 @@ eatmea = raw_meat.rawmerger(''.encode()) #rawlist[0].encode())
 # add every single channel/file in list
 for rf in rawlist :
     print("\nadding channel " + str(rf))
-    succ = eatmea.add_channel(rf.encode())
-    if succ :
+    try :
+        succ = eatmea.add_channel(rf.encode())
         print("\nrecent time series: length: " + str(len(eatmea.get_time_series())) + "\n")
-    else :
-        print("\nfailed to add channel\n")
+    except RuntimeError as e :
+        print("failed to add channel: " + str(e))
 
 # show summary of successfully merged channels
 print("\nmerged channels:\n")
 
 # write merged table to .csv output
-eatmea.write_table_all('allchannels.csv'.encode(),ord(','))
+eatmea.write_table_all('output/allchannels.csv'.encode(),ord(','))
 
 # get number of successfully merged channels and their names (+units)
 numch = eatmea.get_num_channels()
@@ -166,10 +128,10 @@ pyarwtab = pa.Table.from_arrays(pyarrs,chnames)
 print("\n" + 60*"-" + "\n" + str(pyarwtab) + "\n")
 
 # write pyarrow table to .parquet file with compression
-pq.write_table(pyarwtab,'allchannels.parquet',compression='BROTLI')  # compression='BROTLI', 'SNAPPY')
+pq.write_table(pyarwtab,'output/allchannels.parquet',compression='BROTLI')  # compression='BROTLI', 'SNAPPY')
 
 # try to read and decode the .parquet file
-df = pq.read_table('allchannels.parquet')
+df = pq.read_table('output/allchannels.parquet')
 print(df.to_pandas())
 # df.to_pandas().to_csv('allchannels.csv',index=False,encoding='utf-8',sep=",")
 
diff --git a/src/main.cpp b/src/main.cpp
index e76826d..55a37c5 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -9,14 +9,6 @@
 
 int main(int argc, char* argv[])
 {
-//  std::cout<<"number of CLI-arguments: "<<argc<<"\n";
-//  for ( int i = 0; i < argc; i++ ) std::cout<<std::setw(5)<<i<<":   "<<argv[i]<<"\n";
-
-//  path of filename provided ?
-//  assert( argc > 2 && "please provide a filename and path for input and output" );
-
-//  check number of CLI arguments
-//  assert( argc == 3 );
 
   if ( argc != 3 ) //or ( argc == 1 && std::string(argv[1]) == str::string("--help") )
   {
@@ -29,19 +21,18 @@ int main(int argc, char* argv[])
   // get name/path of file from CLI argument
   std::string rawfile(argv[1]);
 
-  // declare instance of "raw_eater"
-  raw_eater eatraw(rawfile,true);
+  // declare instance of 'raw_eater' (and decode data)
+  raw_eater eatraw; //rawfile,false);
 
-  // declare instance of "raw_merger"
-//  raw_merger eatmea;
-//  eatmea.add_channel(rawfile,true);
-//  eatmea.add_channel("smp/VehicleSpeed_HS.raw",true);
-//  eatmea.add_channel("smp/VehicleSpeed_HS.raw",true);
-//  eatmea.add_channel("smp/Rangerover_Evoque_F-RR534_2019-05-07/Temp_Disc_FR.raw",true);
+  // set file to be decoded
+  eatraw.set_file(rawfile,true);
 
-  //eatraw.show_markers();
+  // do conversion
+  eatraw.setup_and_conversion(false);
 
-//  std::cout<<"\n";
+  // eatraw.show_markers();
+
+  //  std::cout<<"\n";
 //  std::map<std::string,std::vector<unsigned char>> marks = eatraw.get_markers();
 //  for ( auto mrk: marks )
 //  {
@@ -67,10 +58,32 @@ int main(int argc, char* argv[])
   // write data in csv-file
   if ( eatraw.get_valid() )
   {
-    // eatraw.write_table(std::string(argv[2]));
     eatraw.write_table(std::string(argv[2]),' ');
-    // eatmea.write_table(std::string(argv[2]));
-    // eatmea.write_table(std::string(argv[2]),' ');
+  }
+  else
+  {
+    std::cout<<"=> invalid/corrupt .raw file\n";
+  }
+
+//---------------------------------------------------------------------------//
+
+  // declare instance of 'raw_merger'
+  raw_merger eatmea;
+
+  // add channels
+  eatmea.add_channel(rawfile,false);
+  // eatmea.add_channel("smp/VehicleSpeed_HS.raw",true);
+  // eatmea.add_channel("smp/Mercedes_E-Klasse-2019-08-08/Flex_StWhl_AnglSpd.raw",false);
+  // eatmea.add_channel("smp/Rangerover_Evoque_F-RR534_2019-05-07/Temp_Disc_FR.raw",false);
+
+  // write merged table
+  if ( eatmea.get_num_channels() > 0 )
+  {
+    eatmea.write_table_all("output/allchannels.csv",' ');
+  }
+  else
+  {
+    std::cout<<"no valid channel added\n";
   }
 
   return 0;