why Baudrate Setting needs for embedded usb communication

[indira]

Hi,

Greetings!

I have just started working on USB communication between two Embedded devices based on atmel sam9 MPUs.

Current Status:-
  No OS involved. Code written in C.
  Host side, EHCI layer stack is there. (reference: Open source)
  Device side, USB-CDC code is there.(reference: Atmel example code)
  Bulk-in and Bulk-out transfer types are used for data transfer of about 13KBytes; Basically working fine.

  In Device side, Virtual com port setting function is called;
  But i have not included any Get_Line_Code and Set_Line_Code class specific request in Host side.

My doubts is:

1. Can I understand that the communication is purely on BULK transaction, not restricted by baudrate
 and hence in my case, baudrate setting on usb device is just meaningless?

2. I assume Virtual com port settings are used by PCs only, not needed between two embedded devices.
    Am i right?

3. Whether this com port settings are just transferred to Host or Registered in Host controller or Device controller?

4. Please suggest the usb Device class type to achieve maximum transfer between any two embedded systems.

5. If you have any application note/link for achieving maximum usb transfer rate, please share it with me.

Please help me out in understanding these very basic things.

Regards,
Indira




 

[Jan Axelson]

Yes, USB virtual serial ports don't use baud rates or serial-port handshaking.

The maximum transfer rate depends on the transfer type and the efficiency of the drivers in the host and device.

Bulk transfers are fastest on an otherwise idle bus so virtual serial port can be a good choice. When receiving data, try to eliminate NAKs.

Hi,

Greetings!

I have just started working on USB communication between two Embedded devices based on atmel sam9 MPUs.

Current Status:-
  No OS involved. Code written in C.
  Host side, EHCI layer stack is there. (reference: Open source)
  Device side, USB-CDC code is there.(reference: Atmel example code)
  Bulk-in and Bulk-out transfer types are used for data transfer of about 13KBytes; Basically working fine.

  In Device side, Virtual com port setting function is called;
  But i have not included any Get_Line_Code and Set_Line_Code class specific request in Host side.

My doubts is:

1. Can I understand that the communication is purely on BULK transaction, not restricted by baudrate
 and hence in my case, baudrate setting on usb device is just meaningless?

2. I assume Virtual com port settings are used by PCs only, not needed between two embedded devices.
    Am i right?

3. Whether this com port settings are just transferred to Host or Registered in Host controller or Device controller?

4. Please suggest the usb Device class type to achieve maximum transfer between any two embedded systems.

5. If you have any application note/link for achieving maximum usb transfer rate, please share it with me.

Please help me out in understanding these very basic things.

Regards,
Indira