PORTS Forum

Ports and Interfaces => USB => Topic started by: Prasad on March 19, 2014, 02:05:18 am

Title: Is XModem transfers possible in a USB bootloader
Post by: Prasad on March 19, 2014, 02:05:18 am

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

Title: Re: Is XModem transfers possible in a USB bootloader
Post by: Jan Axelson on March 19, 2014, 12:59:43 pm

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

Title: Re: Is XModem transfers possible in a USB bootloader
Post by: Barry Twycross on March 19, 2014, 01:51:45 pm

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.

Title: Re: Is XModem transfers possible in a USB bootloader
Post by: Jan Axelson on March 19, 2014, 03:30:38 pm

Good point, Barry!