I have two Arduino boards, let's call them Arduino_A and Arduino_B. When I connect Arduino_A to my laptop via a USB cable, it sends data over the COM port successfully. Similarly, when I connect Arduino_B to the laptop and send data via the COM port, Arduino_B receives it correctly.
However, when I directly connect Arduino_A to Arduino_B using a USB cable, and power up one Arduino by connecting its programming port to the laptop (which powers both Arduinos), the communication between them doesn't work. Why is that?
I was expecting that the communication will work when connected directly
