Is XModem transfers possible in a USB bootloader

[Prasad]

Hello, I am planning to developing a USB bootloader on lpc435x platform. The earlier design used a usb to uart bridge chip from SiLabs and implemented UART loader with a Xmodem protocol.

Suppose that I would want to use on-chip USB and implement a USB loader instead of using above converter , can the XModem protocol implementation of UART loader be used in  the USB loader alI am going to develop also?

I had earlier experience with a USB bootloader that used YModem protocol.

Thanks in advance
Pra

[Jan Axelson]

Yes, you could do a CDC virtual serial port and implement xmodem in firmware. CDC virtual serial ports require a vendor-provided INF file.

[Barry Twycross]

You can use XModem if you want to, our device used to use that. Its a bit of a waste as USB bulk transfers are reliable, the basic USB protocol already does ACKs, CRC checking and has retry logic, so XModem is superfluous and just slows things down.

Once you have a connection you can just stream the data and be assured that any data which does arrive is good and complete.

[Jan Axelson]

Good point, Barry!