Allow USB2.0 to be used with ps5000a

Author: hmaarrfk

picoscope/ps5000a.py

@@ -177,6 +177,7 @@ def _lowLevelOpenUnit(self, serialNumber):
         # since the user should address this immediately, and we
         # shouldn't let this go as a soft error
         # but I think this should do for now
+        # PICO_POWER_SUPPLY_NOT_CONNECTED or PICO_USB3_0_DEVICE_NON_USB3_0_PORT
         if m == 0x11A or m == 0x11E:
             self.changePowerSource(m)
         else: