I have a brand new Protenta C33 board. After successfully uploaded sketches for a few times, the board suddenly stopped to be recognised by the computer. No serial port be detected and I was not able to upload any new sketch to the board. After press the reset button quickly twice, the green LED turned on and blinked, a DFU port was recognised by Arduino IDE, but with the following error "No monitor available for the port protocol dfu. Could not connect to 20-1 dfu port.". I searched the internet and found out many peoples encounters similar problem.
Hi @mkieong
This typically occurs when something in the sketch program interferes with the code that causes the board to produce a USB CDC serial port. The sketch program is running on the same microcontroller that produces the serial port. The interference might be an expected result of your sketch code (e.g., putting the board to sleep to save power), or caused by a bug in the code that is crashing the microcontroller (e.g., dividing by zero).
You can verify this by selecting File > Examples > 01.Basics > BareMinimum from the Arduino IDE menus to open the simple bare minimum sketch, then uploading that sketch to your board. If the problem does not occur when the board is running this "known good" sketch, but the problem does occur when you upload your real sketch again, then you will know that the problem is caused by something in your sketch.
The error is normal and expected.
This error is coming from the Arduino IDE Serial Monitor. The fact you have Serial Monitor running might not be obvious because it is a view in the bottom panel of the Arduino IDE window, and that panel has a tabbed design where it is a container for other views such as the "Output" view. The Serial Monitor is open whenever you see a "Serial Monitor" tab in the bottom panel, even when that tab doesn't have focus in the panel. As the name implies, Serial Monitor is a tool for communicating with the board over the serial port. Serial Monitor is not able to open the DFU port presented by the board, so when you select the DFU port of the board while Serial Monitor is running, it shows this message.
This does not affect the ability to upload to the board in any way. So just disregard the message from Serial Monitor and perform an upload as usual.
Got it! Thanks for the reply. It is really helpful.
You are welcome. I'm glad if I was able to be of assistance.
Regards, Per