I wonder that I could post a question I faced.
Hi, all.
I implemented USB CDC spec on the pxa270 reference board. I correctly send descriptors as Host requested and It works fine in AMD CPU hosted. but other Host which is Intel based can not recognize Descriptors.
I traced routine by inserting printf() and find out that Host can not take a Device descriptor that is requested by host second. (first descriptor before reset by host is correctly recognized.)
I know that OS will manage Enumeration steps but either Computer has same OS WinXP SP3.
Has anyone experienced this problem?
Thanks in advance. ------------------ Shin Jaeyong
Oops! Thanks Tsuneo :)
I'm just new to embedded system programming and I already have one. ;)
Thanks and regards Shin Jaeyong.
For "move memory" operation, like above routine, we don't need to care of the endianness of the core. In either endian, the byte order of the source memory is preserved on the target. When the core exchanges literals or variables with the USB side, endianness of the core concerns.
USB memory is assigned to the endpoint buffers in 32-bit word boundary, which matches to the core operation. The extra padding bytes don't do any harm, when the packet size doesn't fit to the word boundary. Then, copy up to the next word boundary, as it is.
Tsuneo