Structure of payload in data packet when USB initialized as COM port with Serial

Using Arduino Networking, Protocols, and Devices
1

The USB communication has 4 types of packets.

  1. Token Packet (Commonly used for device identification and transaction initiation.)
  2. Data Packet (Contains the data that needs to be transferred from host to client or vice-versa.)
  3. Acknowledgement Packet (Acknowledgement for error-free data reception.)
  4. Special Packets (Hub to hub communication and speed differential.)

When we initiate USB as serial com port using library serial,

The data being transmitted or received is inserted in the data packet at payload section.

I wish to know how this data is structured in payload and how does the baud rate affect this communication or the data.

Thank you very much in advance for any useful answer.

2

I wish to know how this data is structured in payload and how does the baud rate affect this communication or the data

The baud rate doesn't affect this communication it's just sent as an information to the other end to allow to adapt the hardware speed if necessary (p.e. if a FTDI chip is used).

You can find the data structures in the source code delivered with every Arduino IDE. Look at the directory hardware/arduino/core/arduino, the file of most interest is USBCore.h.