updating snapshot and loading datasets

app/spectralanalysis.py

@@ -19,6 +19,7 @@ class SpectralAnalysis:
         self.bs.stop()
         self.channel = None
         self.channels = [channel_dict[x] for x in names]
+        self.hasBStream=False
 
     def connect_name(self, name):
         index = names.index(name)
@@ -30,7 +31,12 @@ class SpectralAnalysis:
         self.channel = self.channels[ich]
         print('Connecting to BS-Channel:',self.channel)
         self.bs.channels.clear()
-        self.bs.get_vars(self.channel)  # this starts the stream into the cache
+        self.hasBStream=True
+        try:
+            self.bs.get_vars(self.channel)  # this starts the stream into the cache
+        except ValueError:
+            print('Cannot find requested channels in BS stream')
+            self.hasBStream=False            
         self.pv = PV(self.channel[0].replace('_Y','_X'))
 
     def terminate(self):