diff --git a/python/esptool-3.0/esptool.py b/python/esptool-3.0/esptool.py
index 99fee40..6f1fdea 100644
--- a/python/esptool-3.0/esptool.py
+++ b/python/esptool-3.0/esptool.py
@@ -473,7 +473,22 @@ def _connect_attempt(self, mode='default_reset', esp32r0_delay=False):
         #
         # DTR & RTS are active low signals,
         # ie True = pin @ 0V, False = pin @ VCC.
-        if mode != 'no_reset':
+        if mode == 'passthru':
+            self._setDTR(False)  # IO0=HIGH
+            # self._setRTS(True)   # EN=LOW, chip in reset
+            time.sleep(0.1)
+            # if esp32r0_delay:
+            #     # Some chips are more likely to trigger the esp32r0
+            #     # watchdog reset silicon bug if they're held with EN=LOW
+            #     # for a longer period
+            #     time.sleep(1.2)
+            self._setRTS(False)  # EN=HIGH, chip out of reset
+            time.sleep(4.0)      # Wait for firmware to start
+            self._setDTR(True)   # IO0=LOW
+            time.sleep(0.2)
+            self._setDTR(False)  # IO0=HIGH, done
+            time.sleep(0.2)
+        elif mode != 'no_reset':
             self._setDTR(False)  # IO0=HIGH
             self._setRTS(True)   # EN=LOW, chip in reset
             time.sleep(0.1)
@@ -3284,7 +3299,7 @@ def main(custom_commandline=None):
     parser.add_argument(
         '--before',
         help='What to do before connecting to the chip',
-        choices=['default_reset', 'no_reset', 'no_reset_no_sync'],
+        choices=['default_reset', 'no_reset', 'no_reset_no_sync', 'passthru'],
         default=os.environ.get('ESPTOOL_BEFORE', 'default_reset'))
 
     parser.add_argument(
diff --git a/targets/dupletx_tx.ini b/targets/dupletx_tx.ini
index 8fe4d51..1f6d961 100644
--- a/targets/dupletx_tx.ini
+++ b/targets/dupletx_tx.ini
@@ -17,3 +17,8 @@ extends = env:DUPLETX_TX_Backpack_via_UART
 
 [env:DUPLETX_TX_Backpack_via_WIFI]
 extends = env:DUPLETX_TX_Backpack_via_UART
+
+[env:DUPLETX_TX_Backpack_via_PASSTHRU]
+extends = env:DUPLETX_TX_Backpack_via_UART
+upload_speed = 230400
+upload_command = python "$PROJECT_DIR/python/esptool-3.0/esptool.py" -b $UPLOAD_SPEED ${UPLOAD_PORT and "-p "+UPLOAD_PORT} -c esp8266 --before passthru --after soft_reset write_flash 0x0000 "$SOURCE"
diff --git a/targets/happymodel_tx.ini b/targets/happymodel_tx.ini
index fd68200..40548df 100644
--- a/targets/happymodel_tx.ini
+++ b/targets/happymodel_tx.ini
@@ -12,3 +12,8 @@ build_flags =
 
 [env:HappyModel_TX_Backpack_via_WIFI]
 extends = env:HappyModel_TX_Backpack_via_UART
+
+[env:HappyModel_TX_Backpack_via_PASSTHRU]
+extends = env:HappyModel_TX_Backpack_via_UART
+upload_speed = 230400
+upload_command = python "$PROJECT_DIR/python/esptool-3.0/esptool.py" -b $UPLOAD_SPEED ${UPLOAD_PORT and "-p "+UPLOAD_PORT} -c esp8266 --before passthru --after soft_reset write_flash 0x0000 "$SOURCE"