Ucom/Uftdi Thru-put

[User Tomdean]

I changed the input buffer size.  The read reported 382 bytes.  The
buffer is 6*(4*16)==384 bytes long.  On the scope I see 6 distinct
groupings in the USB data stream.  Looks like ucom/uftdi, or something
up the chain, is using 64 bytes anyway.  Every 64 bytes, there seem to
be 2 bytes not from the data stream.  Uftdi.c subtracts 2 from count,
giving 382 bytes.

tomdean

/*
 * These are the maximum number of bytes transferred per frame.
 * The output buffer size cannot be increased due to the size encoding.
       ^^^^^^
 */
#define UFTDIIBUFSIZE 384
#define UFTDIOBUFSIZE 64

I sent all 'a' == 0x61.  Using gdb,

(gdb) p/x buf
$5 = {0x61616161 <repeats 15 times>, 0x60316161, 
  0x61616161 <repeats 15 times>, 0x60316161, 0x61616161 <repeats 15 times>, 
  0x60316161, 0x61616161 <repeats 15 times>, 0x60316161, 
  0x61616161 <repeats 15 times>, 0x60316161, 0x61616161 <repeats 15 times>, 
  0x6161,
^^^^ 382 bytes ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  0x0 <repeats 53 times>, 0x28052842, 0x0, 0x0, 0x0, 0x280695d8, 0xe8, 
  0x2813bda4, 0xbfbfe11c, 0x28052d83, 0xe8, 0x0, 0x2813c000, 0x14000, 
  0x28070100, 0x280695d8, 0x2813bda4, 0x28052d61, 0x28070100, 0x0, 0xe8, 
  0x28052d42, 0x280695d8, 0xbfbfe170, 0xbfbfe15c, 0x280527c1, 0xe8, 0x14000, 
  0x3, 0x1012, 0xffffffff, 0x280695d8, 0xbfbfe1cc, 0x28052428, 0x280695d8, 
  0x0, 0xbfbfe1cc, 0x28069bd4, 0x28069bf4, 0x2806f020, 0x0, 0x0, 0x25c, 0x3, 
  0x28137000, 0xc6000, 0x0, 0xda000, 0x28076000, 0x0, 0x0, 0x0, 0x28069c14, 
  0x2804e81a, 0x11, 0x0, 0x280701a0, 0x280695d8, 0x280509a9, 0x280695d8, 
  0xbfbfe44c, 0x2804f785, 0x28070100, 0x0, 0xbfbfe3d4, 0x2804f599, 0x0, 0x0, 
  0x0, 0x6, 0x0 <repeats 27 times>, 0x28059cca, 0xc5, 0x0, 0x0, 0x8000, 0x3, 
  0x1002, 0xffffffff, 0x0, 0x0, 0x0, 0x0, 0x280541ce, 0xc5, 0x280695d8, 
  0xbfbfe2dc, 0x28052c98, 0x0, 0x8000, 0x3, 0x1002, 0xffffffff, 0x0, 0x0, 
  0x2805296a, 0x0, 0x0, 0x1000, 0x28050e72, 0x28089994, 0x28089994, 
  0xbfbfe30c, 0x28050df6, 0x2, 0x280857b4, 0xbfe30c, 0x280695d8, 0x28072020, 
  0x0, 0xbfbfe32c, 0x28050da1, 0x28089994, 0x9a6322b, 0x28070100, 0x0...}