Lock while scanning

Author: alexforencich

vxi11/vxi11.py

@@ -1048,42 +1048,48 @@ def find_listeners(self, address_list=None):
 
         found = []
 
-        for addr in address_list:
-            # check for listener at primary address
-            cmd = bytearray([GPIB_CMD_UNL, GPIB_CMD_UNT])
-            cmd.append(self._bus_address | GPIB_CMD_TAD) # spec says this is unnecessary, but doesn't appear to work without this
-            if type(addr) == tuple:
-                addr = addr[0]
-            if addr < 0 or addr > 30:
-                raise Vxi11Exception("Invalid address", 'find_listeners')
-            cmd.append(addr | GPIB_CMD_LAD)
-            self.send_command(cmd)
-            self.set_atn(False)
-            time.sleep(0.0015) # probably not necessary due to network delays
-            if self.test_ndac():
-                found.append(addr)
-            else:
-                # check for listener at any sub-address
+        try:
+            self.lock()
+            for addr in address_list:
+                # check for listener at primary address
                 cmd = bytearray([GPIB_CMD_UNL, GPIB_CMD_UNT])
                 cmd.append(self._bus_address | GPIB_CMD_TAD) # spec says this is unnecessary, but doesn't appear to work without this
+                if type(addr) is tuple:
+                    addr = addr[0]
+                if addr < 0 or addr > 30:
+                    raise Vxi11Exception("Invalid address", 'find_listeners')
                 cmd.append(addr | GPIB_CMD_LAD)
-                for sa in range(31):
-                    cmd.append(sa | GPIB_CMD_SAD)
                 self.send_command(cmd)
                 self.set_atn(False)
                 time.sleep(0.0015) # probably not necessary due to network delays
                 if self.test_ndac():
-                    # find specific sub-address
+                    found.append(addr)
+                else:
+                    # check for listener at any sub-address
+                    cmd = bytearray([GPIB_CMD_UNL, GPIB_CMD_UNT])
+                    cmd.append(self._bus_address | GPIB_CMD_TAD) # spec says this is unnecessary, but doesn't appear to work without this
+                    cmd.append(addr | GPIB_CMD_LAD)
                     for sa in range(31):
-                        cmd = bytearray([GPIB_CMD_UNL, GPIB_CMD_UNT])
-                        cmd.append(self._bus_address | GPIB_CMD_TAD) # spec says this is unnecessary, but doesn't appear to work without this
-                        cmd.append(addr | GPIB_CMD_LAD)
                         cmd.append(sa | GPIB_CMD_SAD)
-                        self.send_command(cmd)
-                        self.set_atn(False)
-                        time.sleep(0.0015) # probably not necessary due to network delays
-                        if self.test_ndac():
-                            found.append((addr, sa))
+                    self.send_command(cmd)
+                    self.set_atn(False)
+                    time.sleep(0.0015) # probably not necessary due to network delays
+                    if self.test_ndac():
+                        # find specific sub-address
+                        for sa in range(31):
+                            cmd = bytearray([GPIB_CMD_UNL, GPIB_CMD_UNT])
+                            cmd.append(self._bus_address | GPIB_CMD_TAD) # spec says this is unnecessary, but doesn't appear to work without this
+                            cmd.append(addr | GPIB_CMD_LAD)
+                            cmd.append(sa | GPIB_CMD_SAD)
+                            self.send_command(cmd)
+                            self.set_atn(False)
+                            time.sleep(0.0015) # probably not necessary due to network delays
+                            if self.test_ndac():
+                                found.append((addr, sa))
+            self.unlock()
+        except:
+            self.unlock()
+            raise
 
         return found