Happy to help...

I finally got it working, after reading a large number of postings. The issue is with the DTREnable and RTSEnable properties set to false, they need to be set to true, even though there is no handshake (HandShake: none), the virtual port requires this to trigger the data retrieval.
I hope this helps you as it helped me.

I am having exactly the same issue, no responses?

Can anyone tell me what is the MCU on the Arduino NANO 3, is it an ATMEGA328p-au or an ATMEGA328-au?

Thanks for your help, but if anyone needs to do it, this is the code I used to get a 4MHz at 50% duty cicle on pin 3:

pinMode(3, OUTPUT);
TCCR2A = 0x23;
TCCR2B = 0x09;
OCR2A = 3;
OCR2B = 1;

With this I get a very nice square wave that I am using as a clock signal for a smart card.

I hope someone can help me with this, I need to generate a 4MHz signal at 50% duty cicle using a PWM pin. It can be any of the PWM pins, can anyone help me with this. Thanks.

Is there an easy way to know if the Wire.begin() has already been called?
I am creating a library and I want to call it only if it has not been done already.