This means a custom function in pff_diskio.c, disk_parsep(),
which replaces disk_readp(). Now it no longer reads a whole
sector for every single byte, but only once per line of G-code.
Performance is now much better than with buffered reading, the
1 MB file with 16'468 lines of comments, 64 bytes per line,
read and parses now in just 46 seconds, which means 358 lines
or 22'795 bytes per second.
Unfortunately all the binary size loss is gone compared to the
previous version, we're 68 bytes bigger than before buffer-less
parsing. Reason is the new function disk_parsep() in
pff_diskio.h. RAM usage is still low.
ATmega... '168 '328(P) '644(P) '1280
FLASH: 22276 bytes 155.39% 72.51% 35.09% 17.27%
RAM: 1331 bytes 129.98% 64.99% 32.50% 16.25%
EEPROM: 32 bytes 3.12% 1.56% 1.56% 0.78%
Formerly we took efforts to read only small chunks into a
(small) buffer, just to read this buffer byte by byte yet
again for parsing. It's more efficient and requires less
code to parse the character at read time directly. This
way we can read in chunks of exactly one line, making the
buffer obsolete.
First step is to implement this in mendel.c and in sd.c/.h.
This gets rid of the buffer already.
Very inefficient in pff.c and pff_diskio.c so far, more
than 40 minutes / less than 500 bytes/s for reading this
1 MB comments file. Reason is, for every single byte a
whole sector is read. Nevertheless, this attempt appears
to be on the right track.
Binary is 156 bytes smaller, 16 bytes less RAM:
ATmega... '168 '328(P) '644(P) '1280
FLASH: 22052 bytes 153.82% 71.78% 34.73% 17.09%
RAM: 1331 bytes 129.98% 64.99% 32.50% 16.25%
EEPROM: 32 bytes 3.12% 1.56% 1.56% 0.78%
Let the preprocessor decide wether this piece of code is compiled
at all. Previous behaviour was to compile it unconditionally and
rely on the optimizer to remove it after that. Trusting the
optimizer is fine, but only if the code is warning-free in all cases.
This is all the commands to read from and write to SPI,
initializing the card, read in blocks and so on. This should
make Petit FatFs actually usable.
So far read-only and no M-codes to let end users play with
this stuff.
The demonstration code was changed to list the SD card's
top level directory over and over again.
Some modifications to avoid file name conflicts with other parts and
make it compile. As the glue code to the hardware (spi.c/.h) is
still missing, there are a few warnings, of course.
Changes to this library are tracked in pff.c.
Markus Hitter