edit

modbus_tk/modbus_rtu.py

@@ -129,7 +129,8 @@ class RtuMaster(Master):
         self._serial.write(request)
         self._serial.flush()
         print(expected_length)
-        response = self._serial.read(30)
+        expected_length = int(expected_length)
+        response = self._serial.read(expected_length)
         print(response)
         return response