added buffer for different size reads and recovery from failed streaming sessions

joulelabjack/u3_module.py

@@ -109,6 +109,8 @@ class U3Reader(ReaderModule):
 
         # set up timestamps
         data_ts = int(time.time()*1e6)
+        # initialize the buffer
+        self.buffer = [[] for x in range(len(channels))]
         try:
             device = self._setup_u3(channels, parsed_args.rate)
             device.streamStart()
@@ -131,23 +133,38 @@ class U3Reader(ReaderModule):
             device.close()
         except LabJackPython.LabJackException as e:
             print("LabJack Error: "+str(e))
-        except:
-            print("".join(i for i in traceback.format_exc()))
 
     def build_block(self,r,data_ts,data_ts_inc,channels):
-        data = [r['AIN%d'%c] for c in channels]
-        rows = len(data[0])
-        block = np.empty((rows,len(channels)+1))
-        top_ts = data_ts + rows * data_ts_inc
+        # raw data may different sample counts per channel
+        raw_data = [r['AIN%d'%c] for c in channels]
+        # add in any buffered data
+        data = [self.buffer[i]+raw_data[i] for i in range(len(channels))]
+        # put extra data in the buffer
+        shortest_row = min([len(d) for d in data])
+        longest_row = max([len(d) for d in data])
+        self.buffer = [d[shortest_row:longest_row] for d in data]
+        sys.stderr.write(repr(self.buffer)+"\n")
+        
+        # work with uniform data size
+        data = [d[:shortest_row] for d in data]
+        nrows = shortest_row
+        block = np.empty((nrows,len(channels)+1))
+        top_ts = data_ts + nrows * data_ts_inc
         ts = np.array(np.linspace(data_ts, top_ts,
-                                  rows, endpoint=False), dtype=np.uint64)
+                                  nrows, endpoint=False), dtype=np.uint64)
         block = np.vstack((ts,*data)).T
         return (top_ts, block)
 
     def _setup_u3(self, channels, rate):
 
         device = u3.U3()
+        try:
+            device.streamStop()
+            sys.stderr.write("warning: stopped a previous stream\n")
+        except:
+            pass
         device.configU3()
+        
         # set all IO channels to analog signals
         device.configIO(FIOAnalog=0xFF, EIOAnalog=0xFF)