Hello,

I'm designing simple protocol for a bootloader, which is supposed to
transfer data from host computer to target (ARM7-based embedded system)
over
USB. It should not be very reliable, so a simple checksum algorithm can
be
used by now. I plan to transmit data in blocks, prepended with a header
and
ended with a control check sum.

So here is how I assume it may be:

|message type 1 byte|length 2 bytes|... data ...|checksum 4 bytes|

Message type might be 'start', 'stop', 'acknowledge', 'error'. Next is
the size of the data transmitted including header and checksum. It ends
up with the checksum.

I'm not sure to include checksum or not, as USB already supports
error-checking on a hardware level.

Please critisize such solution. Any advices and comments will be
welcomed!