I have a problem while uploading to Arduino Pro Mini

Development Tools IDE 2.x
1

I connected FT232rl to pro mini and dowloanded drivers. FT232 shows in device manager and works in FT Prog but when I click upload in IDE it shows:

avrdude: ser_open(): can't open device "\.\COM3": Access denied.

I also tried to program it through Arduino UNO. But it either shows the same message or uploads for ~5 min then it tells me that it tried 10 times and doesn't got answear.

2

Hi @bartek_bawer. Which version of Arduino IDE are you using (e.g., "2.3.2")? The version is shown on the window title bar and also in the dialog that opens when you select Help > About (or Arduino IDE > About Arduino IDE for macOS users) from the Arduino IDE menus.

I ask for this information because I want to give you the appropriate instructions for the IDE version you are using.

3

I am using Arduino IDE 2.3.2 on Windows

4

There is a known bug in Arduino IDE 2.x that can cause uploads to fail with this "Access is denied" error if you try uploading to a board using an FTDI FT232R USB chip while the Arduino IDE Serial Monitor or Serial Plotter is open.

A port can only be used by one process at a time, so Arduino IDE must automatically close the port in Serial Monitor and Serial Plotter during an upload, automatically opening it again after. For some reason, that juggling of the port control is not working with boards that have the FTDI USB chip.

If that bug is the cause of the problem you are having, the workaround will be to manually close the port in Serial Monitor/Serial Plotter before doing an upload. Please give that a try and then let me know if you still have the error while uploading:

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
  2. Upload the sketch.
  3. 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.

Serial Plotter

If you have the "Serial Plotter" window open, the procedure is a bit different from closing the Serial Monitor connection:

  1. Close the "Serial Plotter" window.
  2. 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 in Serial Plotter
  3. Click the X icon on the "Serial Monitor" tab in the bottom panel of the Arduino IDE window to close the tab:
    image
  4. Upload the sketch.
  5. Open Serial Monitor and/or Serial Plotter again if needed after the upload is finished.

Please let me know if you have any questions or problems while following those instructions.

5

Everything is now working. I had closed Serial monitor, but turning it on and off worked. Thanks for help.

6

You are welcome. I'm glad it is working now.

Regards,
Per

7

After using it for a bit, it suddenly stopped working again. I turn on and off Serial monitor to upload, bu now it is just stuck at uploading and after some time it shows:

avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x6b

Is there a way to permament fix?

8

It seems to work on my other arduino pro mini (but this is 5V version and not 3.3V that I need). The orignal board is working, beacuse it connects to serial monitor (that I turn off to upload) and I see that the previously uploaded code is still working.

9

Select Tools > Processor > ATmega328P (3.3V, 8 MHz) from the Arduino IDE menus and then try uploading again.

10

I selected the corrected one, even tried on diffrent ones, but still not working.

11

How do you have the FT232RL connected to the Pro Mini?

Is it a module plugged directly into the header on the Pro Mini, something like you see here?:

image

Or is it connected via jumper wires? If so, please provide the list of each pin's connection from the FT232R to the Pro Mini.

12

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