How do I communicate from microcontroller to PC without a virtual COM port?

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I am trying to create a programmable Keyboard with an Arduino. It was actually pretty easy, just using the keyboard library, printing a character when a button is pressed: no problems. I also created an application on the PC to communicate over the serial port with the Arduino, I can send a new configuration and tell the Arduino which character I want when button 1 is pressed: a bit more complicated but still ok.

My problem: I do not want the communication between Arduino and PC to be over serial port.
- serial port number changes sometimes
- another application can "steal" the port and kill the communication
- it is not crypted

What are my options to communicate between Arduino/Microcontroller and PC?

What I have tried:

I looked into HID and CDC protocol, I use HID report so that my Arduino is recognized as a keyboard by the PC. I think CDC is actually currently used for the serial communication of the Arduino.

A perfect solution would be a CDC class which allows me to communicate like a regular serial port, but would somehow be "hidden". I would be able to find the USB device with PID and VID.

Posted 28-Sep-17 11:14am

Member 12254962

Updated 28-Sep-17 21:18pm

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Jochen Arndt · Answer 1 · 2017-09-28T21:18:00

Quote:
- serial port number changes sometimes

That might happen when plugging the USB-to-Serial converter into a different connector. But it should not happen when not unplugging the converter.

Quote:
- another application can "steal" the port and kill the communication

COM ports are exclusive resources. That applies to virtual ports too. That means once an application has opened it, it can't be opened anymore by another application (or even the same application). So the communication can't be killed by another application. However, another application may open the port before yours.

Quote:
- it is not crypted

That is not related to the physical interface and low level communication protocol. If necessary, you can use some kind of encryption for data transfers.

Quote:
What are my options to communicate between Arduino/Microcontroller and PC?

There are many depending on the kind of interfaces available or installable. For low speed you can even use SPI and I2C.

I assume that you have an USB-to-Serial converter at the PC side. If that has an FTDI chip, you can use the D2XX Direct Drivers[^] (with other chips there may be similar drivers). Using that you can access the converter by VID and PID instead of the virtual COM port and avoid the problem of changing COM ports. You can even uninstall or disable the virtual COM port driver so that other applications would have to use the same method to access the converter.