ok here's are some ideas for you, after glancing through the pic32 manual..=
..

1) if you can reserve a byte value as a end of file marker, just do the=20
pattern match thing.  I think you said this wouldn't work.

2) send a fixed length header block which basically contains the length=20
of the next block - I.E. a few byte header.   Receive that small header=20
block, parse it, and then configure the dma controller to receive the=20
size block it indicates.

In reality, I'd probably just give the DMA block a chunk of memory to=20
work in, and just let it have at it.   Treat it as a ring buffer - with=20
the knowlege that you can ignore it for a large chunk of time.  Then use=20
the header information to parse out the data.   I.E.

0x55 0xAA  - header value
0x01 0x00 - data length  (0x100 bytes)
(0x100 bytes of data here)
0x?? 0x?? - checksum.

Once the DMA starts receiving data, the pointers in the DMA module which=20
say where it is going to write is going to change as data is=20
recceived.   So, once you see this, you start looking at data from your=20
'start point'.  You should find a 0x55, then an 0xaa, then two bytes=20
indiciating the length.  once you have this, you can just ignore the DMA=20
until the pointer has moved this far ahead... just poll it every once in=20
a while.  You may also be able to do something where you change the dma=20
transfer length on the fly once you have the data which tells you how=20
long the transfer is.

-forrest
--=20
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