espefuse: Adds external esp instance

Closes #873

espefuse/__init__.py

@@ -132,15 +132,21 @@ def split_on_groups(all_args):
     return groups, used_cmds
 
 
-def main(custom_commandline=None):
+def main(custom_commandline=None, esp=None):
     """
     Main function for espefuse
 
     custom_commandline - Optional override for default arguments parsing
     (that uses sys.argv), can be a list of custom arguments as strings.
     Arguments and their values need to be added as individual items to the list
     e.g. "--port /dev/ttyUSB1" thus becomes ['--port', '/dev/ttyUSB1'].
+
+    esp - Optional override of the connected device previously
+    returned by esptool.get_default_connected_device()
     """
+
+    external_esp = esp is not None
+
     init_parser = argparse.ArgumentParser(
         description="espefuse.py v%s - [ESP32xx] efuse get/set tool"
         % esptool.__version__,
@@ -211,22 +217,24 @@ def main(custom_commandline=None):
 
     print("espefuse.py v{}".format(esptool.__version__))
 
-    try:
-        esp = get_esp(
-            common_args.port,
-            common_args.baud,
-            common_args.before,
-            common_args.chip,
-            just_print_help,
-            common_args.virt,
-            common_args.debug,
-            common_args.path_efuse_file,
-        )
-    except esptool.FatalError as e:
-        raise esptool.FatalError(
-            f"{e}\nPlease make sure that you have specified "
-            "the right port with the --port argument"
-        )  # TODO: Require the --port argument in the next major release, ESPTOOL-490
+    if not external_esp:
+        try:
+            esp = get_esp(
+                common_args.port,
+                common_args.baud,
+                common_args.before,
+                common_args.chip,
+                just_print_help,
+                common_args.virt,
+                common_args.debug,
+                common_args.path_efuse_file,
+            )
+        except esptool.FatalError as e:
+            raise esptool.FatalError(
+                f"{e}\nPlease make sure that you have specified "
+                "the right port with the --port argument"
+            )
+            # TODO: Require the --port argument in the next major release, ESPTOOL-490
 
     efuses, efuse_operations = get_efuses(
         esp, just_print_help, debug_mode, common_args.do_not_confirm
@@ -276,7 +284,7 @@ def main(custom_commandline=None):
             if not efuses.burn_all(check_batch_mode=True):
                 raise esptool.FatalError("BURN was not done")
     finally:
-        if not common_args.virt and esp._port:
+        if not external_esp and not common_args.virt and esp._port:
             esp._port.close()