test: fix failed to download in example test:

1. example test uses auto detect flash size. we need to call
`detect_flash_size` before write flash
2. fix incorrect baudrate used: when using WROVER-Kits, it's likely that download with baudrate 921600
will fail. If we don't reset serial setting in decorator, 921600 will
become the default baudrate. This causes all the subsequent
communication fails
3. do hw reset after used esptool function

tools/tiny-test-fw/IDF/IDFDUT.py

@@ -22,8 +22,6 @@ import tempfile
 
 from serial.tools import list_ports
 
-from collections import namedtuple
-
 import DUT
 
 try:
@@ -51,14 +49,20 @@ def _uses_esptool(func):
 
         settings = self.port_inst.get_settings()
 
-        rom = esptool.ESP32ROM(self.port_inst)
-        rom.connect('hard_reset')
-        esp = rom.run_stub()
+        try:
+            rom = esptool.ESP32ROM(self.port_inst)
+            rom.connect('hard_reset')
+            esp = rom.run_stub()
 
-        ret = func(self, esp, *args, **kwargs)
+            ret = func(self, esp, *args, **kwargs)
+            # do hard reset after use esptool
+            esp.hard_reset()
+        finally:
+            # always need to restore port settings
+            self.port_inst.apply_settings(settings)
 
-        self.port_inst.apply_settings(settings)
         self.start_receive()
+
         return ret
     return handler
 
@@ -94,6 +98,8 @@ class IDFDUT(DUT.SerialDUT):
         except RuntimeError:
             return None
         finally:
+            # do hard reset after use esptool
+            esp.hard_reset()
             esp._port.close()
 
     @classmethod
@@ -121,31 +127,27 @@ class IDFDUT(DUT.SerialDUT):
 
             # fake flasher args object, this is a hack until
             # esptool Python API is improved
-            Flash_Args = namedtuple('write_flash_args',
-                                    ['flash_size',
-                                     'flash_mode',
-                                     'flash_freq',
-                                     'addr_filename',
-                                     'no_stub',
-                                     'compress',
-                                     'verify',
-                                     'encrypt'])
+            class FlashArgs(object):
+                def __init__(self, attributes):
+                    for key, value in attributes.items():
+                        self.__setattr__(key, value)
 
-            flash_args = Flash_Args(
-                self.app.flash_settings["flash_size"],
-                self.app.flash_settings["flash_mode"],
-                self.app.flash_settings["flash_freq"],
-                flash_files,
-                False,
-                True,
-                False,
-                False
-            )
+            flash_args = FlashArgs({
+                'flash_size': self.app.flash_settings["flash_size"],
+                'flash_mode': self.app.flash_settings["flash_mode"],
+                'flash_freq': self.app.flash_settings["flash_freq"],
+                'addr_filename': flash_files,
+                'no_stub': False,
+                'compress': True,
+                'verify': False,
+                'encrypt': False,
+            })
 
             esp.change_baud(baud_rate)
+            esptool.detect_flash_size(esp, flash_args)
             esptool.write_flash(esp, flash_args)
         finally:
-            for (_,f) in flash_files:
+            for (_, f) in flash_files:
                 f.close()
 
     def start_app(self, erase_nvs=ERASE_NVS):
@@ -171,7 +173,9 @@ class IDFDUT(DUT.SerialDUT):
 
         :return: None
         """
-        esp.hard_reset()
+        # decorator `_use_esptool` will do reset
+        # so we don't need to do anything in this method
+        pass
 
     @_uses_esptool
     def erase_partition(self, esp, partition):