Programming issue on IDE 2.3.4

pkdj · January 13, 2025, 4:43pm

Hi I have upgraded my IDE from 1.8.13 to 2.3.4 both running on windows 10 PC.

Took me a while to work out why I was having uploading issues in 2.3.4.

Finally worked out that in 2.3.4 you must close the serial monitor before uploading otherwise there is a "COM port access denied error".

Did not have to do this in 1.8.13.

Is there a config setting in 2.3.4 somewhere that will automatically do this so it operates same way as 1.8.13.

1.8.13 still works fine but thought it was a bout time I upgraded

Not a major issue but just a bit of a niggle.

Thanks

Paul

ptillisch · January 13, 2025, 4:45pm

Hi @pkdj. Thanks for taking the time to share your findings.

Does the board you were using when you experienced this problem have an FTDI FT232R USB chip?

pkdj · January 13, 2025, 4:52pm

Its a 5V 16Hz pro mini from AZ Delivery and I'm using the sparkfun USB FTDI interface.

ptillisch · January 13, 2025, 8:00pm

Thanks for the confirmation. The Arduino IDE developers are tracking that bug here:

github.com/arduino/arduino-ide

"Access is denied" error when uploading to board w/ FT232 USB chip with Serial Monitor/Plotter open

opened 07:07AM - 23 Dec 22 UTC

maciejmiklas

topic: code type: imperfection

### Describe the problem In order to upload to an Arduino board via a serial po…rt, the upload tool (e.g., [**AVRDUDE**](https://github.com/avrdudes/avrdude)) must be able to open the port. This is not possible if another process already has control of the port. Arduino IDE's "Serial Monitor" and and "Serial Plotter" components also use the serial port of the board. Arduino IDE handles this potential conflict of port usage automagically by closing the port in Serial Monitor/Plotter when an upload process is triggered, then opening it again after the upload is finished. This means no special action is needed from the user to upload while Serial Monitor/Plotter is open. 🐛 The upload fails with an "`Access is denied`" error under the following conditions: - The board uses an FTDI FT232R USB chip - Arduino IDE is running on a Windows machine - Serial Monitor or Serial Plotter is open I've been using Arduino IDE 2.0.3 with Nano without issues when uploading on Ubuntu. Now I've tried it on Windows 11, and most of the time, it gives me this error: ```text avrdude: Version 6.3-20190619 Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/ Copyright (c) 2007-2014 Joerg Wunsch System wide configuration file is "C:\Users\macie\AppData\Local\Arduino15\packages\arduino\tools\avrdude\6.3.0-arduino17/etc/avrdude.conf" Using Port : COM5 Using Programmer : arduino Overriding Baud Rate : 115200 avrdude: ser_open(): can't open device "\\.\COM5": Access is denied. ``` But I can see logs from the serial monitor in Arduino IDE -> serial monitor. ### To reproduce #### Equipment A board or other device that has an [FTDI FT232R USB chip](https://ftdichip.com/products/ft232rl/) The [classic **Arduino Nano**](https://docs.arduino.cc/hardware/nano) is a common board that uses this chip. FT232R modules ([example](https://docs.arduino.cc/retired/other/usb-serial-converter)) or cables ([example](https://www.sparkfun.com/products/9717)) are also often used to upload to boards such as the [**Arduino Pro Mini**](https://www.sparkfun.com/products/11113) that don't have an integrated USB chip. The fault can be reproduced even if the FT232R-based device is not an Arduino board. In this case, the upload is expected to fail, but it would fail with a "`not in sync`" error instead of "`Access is denied`". #### Steps 1. Select **File > New Sketch** from the Arduino IDE menus. 1. Connect the Arduino board to your computer. 1. Select the board and port from the Arduino IDE menus. 1. If the Serial Monitor view is not already open, select **Tools > Serial Monitor** from the Arduino IDE menus to open it. 1. Select **Sketch > Upload** from the Arduino IDE menus. 1. Wait for the upload process to finish. 🐛 The upload fails: ```text avrdude: Version 6.3-20190619 Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/ Copyright (c) 2007-2014 Joerg Wunsch System wide configuration file is "C:\Users\macie\AppData\Local\Arduino15\packages\arduino\tools\avrdude\6.3.0-arduino17/etc/avrdude.conf" Using Port : COM5 Using Programmer : arduino Overriding Baud Rate : 115200 avrdude: ser_open(): can't open device "\\.\COM5": Access is denied. ``` 1. Click the **X** icon on the "**Serial Monitor**" view tab in the bottom panel. 1. Select **Sketch > Upload** from the Arduino IDE menus. 1. Wait for the upload process to finish. 🙂 The upload is successful. 1. Select **Tools > Serial Plotter** from the Arduino IDE menus. 1. Select **Sketch > Upload** from the Arduino IDE menus. 1. Wait for the upload process to finish. 🐛 The upload fails: ```text avrdude: Version 6.3-20190619 Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/ Copyright (c) 2007-2014 Joerg Wunsch System wide configuration file is "C:\Users\macie\AppData\Local\Arduino15\packages\arduino\tools\avrdude\6.3.0-arduino17/etc/avrdude.conf" Using Port : COM5 Using Programmer : arduino Overriding Baud Rate : 115200 avrdude: ser_open(): can't open device "\\.\COM5": Access is denied. ``` 1. Close the "**Serial Plotter**" window. 1. Select **Sketch > Upload** from the Arduino IDE menus. 1. Wait for the upload process to finish. 🐛 The upload fails: ```text avrdude: Version 6.3-20190619 Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/ Copyright (c) 2007-2014 Joerg Wunsch System wide configuration file is "C:\Users\macie\AppData\Local\Arduino15\packages\arduino\tools\avrdude\6.3.0-arduino17/etc/avrdude.conf" Using Port : COM5 Using Programmer : arduino Overriding Baud Rate : 115200 avrdude: ser_open(): can't open device "\\.\COM5": Access is denied. ``` **ⓘ** This unexpected result is caused by a separate bug: https://github.com/arduino/arduino-ide/issues/1423 ### Expected behavior Serial Monitor and Serial Plotter do not interfere with upload process. ### Arduino IDE version #### Original report 2.0.3 #### Last verified with 2.3.3 ### Operating system Windows ### Operating system version Edition Windows 11 Pro Version 22H2 Installed on 07/11/2022 OS build 22621.963 Experience Windows Feature Experience Pack 1000.22638.1000.0 ### Additional context I bisected the introduction of the fault to df8658e --- Logs generated from an upload that fails with this fault using the build for 053574b with the `arduino.cli.daemon.debug` [advanced setting](https://github.com/arduino/arduino-ide/blob/main/docs/advanced-usage.md#advanced-settings) set to `true`: [2023-08-16_log.log](https://github.com/arduino/arduino-ide/files/12357046/2023-08-16_log.log) --- I have no problems uploading sketches on Arduino IDE 1.8.19 from Microsoft Store on the same system. I can quit 2.0.3, start 1.8.19, and it's working immediately. --- I cannot reproduce the fault on Linux (Ubuntu 22.04) or macOS (Ventura). --- I cannot reproduce the fault when using native USB boards (e.g., [**Leonardo**](https://docs.arduino.cc/hardware/leonardo), [**MKR**](https://docs.arduino.cc/#mkr-family)) or boards that use other models of dedicated USB chip (e.g., ATmega16U2 on Uno and Mega, WCH CH340 on derivative boards). <a name="workaround"></a> #### Workaround <a name="serial-monitor"></a> ##### Serial Monitor 1. Click the **X** icon on the "**Serial Monitor**" tab in the bottom panel of the Arduino IDE window to close the tab: ![image](https://user-images.githubusercontent.com/8572152/215050213-e6c41c1a-0eae-448a-ae91-f2acefedf793.png) 1. Upload the sketch. 1. Open **Serial Monitor** again if needed (by clicking the icon on the IDE toolbar or the **Tools > Serial Monitor** menu item) after the upload is finished. <a name="serial-plotter"></a> ##### Serial Plotter 1. Close the "**Serial Plotter**" window. 1. If the "**Serial Monitor**" view is not already open, select **Tools > Serial Monitor** from the Arduino IDE menus to open it. **ⓘ** We must do an open/close cycle on **Serial Monitor** as a workaround for [a bug](https://github.com/arduino/arduino-ide/issues/1423) in **Serial Plotter** 1. Click the **X** icon on the "**Serial Monitor**" tab in the bottom panel of the Arduino IDE window to close the tab: ![image](https://user-images.githubusercontent.com/8572152/215050213-e6c41c1a-0eae-448a-ae91-f2acefedf793.png) 1. Upload the sketch. 1. Open **Serial Monitor** and/or **Serial Plotter** again if needed after the upload is finished. #### Additional reports - https://github.com/arduino/arduino-ide/issues/1937 - https://github.com/arduino/arduino-ide/issues/726#issuecomment-1464313325 - https://github.com/arduino/arduino-ide/issues/1783#issuecomment-1614370292 - https://github.com/arduino/arduino-ide/issues/1783#issuecomment-2196936864 - https://forum.arduino.cc/t/brand-new-nano-wont-connect-to-latestide-software/1129473/10 - https://forum.arduino.cc/t/arduino-nano-not-able-to-upload-comx-port-access-denied/1081669/15 - https://forum.arduino.cc/t/elusive-uno-upload-error-access-is-denied/1067785/5 - https://forum.arduino.cc/t/fdti-breakout-2-types-cause-usb-acess-denial/1088005 - https://forum.arduino.cc/t/port-access-is-denied/1089761 - https://forum.arduino.cc/t/cant-open-device-when-uploading-but-serial-monitor-works/1127731 - https://forum.arduino.cc/t/2-1-0-no-longer-disables-monitor-during-upload-update/1139065 - https://forum.arduino.cc/t/access-denied-when-uploading-to-arduino-nano/1139330/1 - https://forum.arduino.cc/t/access-denied-when-uploading-to-arduino-nano/1139330/11 - https://forum.arduino.cc/t/2-11-com3-access-is-denied/1143750 - https://forum.arduino.cc/t/cannot-upload-to-arduino-nano/1145391 - https://forum.arduino.cc/t/cant-upload-to-pro-mini-port-access-is-denied/1152460 - https://forum.arduino.cc/t/cannot-upload-to-ftdi-megas-only/1170683 - https://forum.arduino.cc/t/arduinon-nano-access-denied/1181808/6 - https://forum.arduino.cc/t/avrdude-ser-open-cant-open-device/1228096 - https://forum.arduino.cc/t/avrdude-ser-open-cant-open-device-com9-access-is-denied/1205151 - https://forum.arduino.cc/t/exit-status-1-only-sometimes/1180375 - https://forum.arduino.cc/t/have-to-kill-serial-monitor-exe-to-upload-to-the-board/1173764 - https://forum.arduino.cc/t/arduino-nano-not-recognised-correctly/1133051 - https://forum.arduino.cc/t/brand-new-nano-wont-connect-to-latestide-software/1129473 - https://forum.arduino.cc/t/arduino-nano-avrdude-ser-open-cant-open-device-com5-access-is-denied/1124189 - https://forum.arduino.cc/t/i-have-a-problem-while-uploading-to-arduino-pro-mini/1255072 - https://forum.arduino.cc/t/problem-uploading-to-nano/1267124 - https://forum.arduino.cc/t/nano-appears-as-com6-and-doesnt-work/1273314 - https://forum.arduino.cc/t/com-port-disconnects-when-open-arduino-ide/1299780 - https://forum.arduino.cc/t/com-port-issues/1304755 - https://forum.arduino.cc/t/upload-to-pro-mini-fails-avrdude-ser-open-cant-open-device-com8-access-is-denied/1315064 - https://forum.arduino.cc/t/avrdude-ser-open-cant-open-device-com6-access-is-denied/1319310 - https://forum.arduino.cc/t/programming-issue-on-ide-2-3-4/1342261 - https://www.reddit.com/r/arduino/comments/1bhwt6f/access_is_denied_error_on_nano/ #### Related - https://forum.arduino.cc/t/issue-with-flashing-esp32-dev-kit-with-arduino-ide/1117755 - https://forum.arduino.cc/t/port-issues-with-ide-2-0-3/1069090 ### Issue checklist - [X] I searched for previous reports in [the issue tracker](https://github.com/arduino/arduino-ide/issues?q=) - [X] I verified the problem still occurs when using the latest [nightly build](https://www.arduino.cc/en/software#nightly-builds) - [X] My report contains all necessary details

If you have a GitHub account, you can subscribe to that thread to get notifications of any new developments related to this subject:

Until it is fixed, the workaround you found of making sure to close Serial Monitor (and Serial Plotter) before attempting an upload will be effective.

Topic		Replies	Views
Can't upload to my board while serial monitor is open Uploading	11	620	September 2, 2025
Can't upload code to Arduino boards after changing settings Uploading	2	221	February 8, 2026
Failed Upload Ide 2.0 IDE 2.x	18	7033	January 27, 2023
Cannot Upload - to FTDI MEGAs only IDE 2.x	18	639	September 26, 2023
Com port disconnects when open Arduino IDE IDE 2.x	5	571	September 9, 2024

Programming issue on IDE 2.3.4

Related topics