Refactor(#4): optimize scan function

https://www.notion.so/4-Controller-Uart-451f896953eb4e15bd70eeadb17eb94e

python/biopro/device/device_cc2650.py

@@ -2034,22 +2034,32 @@ class CC2650SingleMasterCentralDevice(CC2650MasterDevice, Synchronized):
         ins.append(0xF1)
         self._interface.flush_input()
 
-        try:
-            self.log_verbose('[CC2650]', 'scan_callback att_write','0x'+str.upper(ins.hex()))
-            self._cc2650.send("bytes", bytes(ins))
-
-        except SerialTimeoutException:
-            self.log_verbose('[CC2650]', 'scan_callback send fail')
-
-        else:
+        for _ in range(5):
             try:
-                scan_response = self._cc2650.recv_uart(0.01)
+                self.log_verbose('[CC2650]', 'scan_callback att_write','0x'+str.upper(ins.hex()))
+                self._cc2650.send("bytes", bytes(ins))
 
-            except RecvTimeout:
-                self.log_verbose('[CC2650]', 'scan_callback response timeout, no device')
-                return False
+            except SerialTimeoutException:
+                self.log_verbose('[CC2650]', 'scan_callback send fail, rescan')
+                continue
+
+            else:
+                try:
+                    scan_response = self._cc2650.recv_uart(0.01)
+
+                except RecvTimeout:
+                    self.log_verbose('[CC2650]', 'scan_callback response timeout, no device, rescan')
+                    continue
+
+                else:
+                    if scan_response is None:
+                        self.log_verbose('[CC2650]', 'scan_callback response is None, rescan')
+                        continue
+                    else:
+                        break
 
         if scan_response is None:
+            self.log_verbose('[CC2650]', 'scan_callback response is None--2')
             return False
 
         scan_response_hex = ''.join(format(i, '02X') for i in scan_response)