Does anyone know how the data in data packet looks like when the USB is initialized as COM port?
I have a Arduino Mega 2560. I have initialized COM port with a baud rate of 9600. I know that there are four types of USB packets as
- Token Packet (Commonly used for device identification and transaction initiation.)
- Data Packet (Contains the data that needs to be transferred from host to client or vice-versa.)
- Acknowledgement Packet (Acknowledgement for error-free data reception.)
- Special Packets (Hub to hub communication and speed differential.)
The payload in data packet is formatted as
DATA1 >> PAYLOAD >> CRC16 ; DATA2 >> >> PAYLOAD >> CRC16 ; etc.
Till this point I am clear about whats happening.
Now all I want to know is
- How the data is structured in the PAYLOAD section, when USB is initialized as COM port?
- How the baud rate comes into picture i.e how a particular baudrate is achieved in this type of communication?
- How is communication in terms of packet sequence? Does the sequence of packets change? (Like token>>data>>ack>>data>>ack>>...)
I really need to know this urgently as I am working on program that has to connect with 3 MEga2560 boards through a USB hub. I want to fix my design constraints depending on what is the maximum baud rate that I can achieve for all boards.