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%
Next to the implementation of sd_read_byte() as well as M24 and
M25, yet another demo: read the file and write it to the serial
line, to show correctness of the implementation.
Part 2 is to implement M23: select file. That's more than just a
few lines, as we also have to teach the gcode-parser to collect
strings.
For now the file is simply tested for successful opening, no
actual printing, yet.
About build size: during development there was another
implementation, which didn't abstract SD card functions into
sd.c/.h, but put them into gcode_process.c directly. At the
feature completeness of this commit, the other implementation
used 70 bytes flash less, but also 23 bytes more RAM. So I decided
for the more abstracted/encapsulated version. --Traumflug
Also, this adds 14 bytes binary size even without SD card support.
A lot more #ifdefs around each use of next_target.read_string
would remove this, but after all we do care a bit about
readability of the source code, so let's sacrify these 14 bytes
to it. --Traumflug
Part 1 is, implement
- M20: List SD card.
- M21: Initialize SD card (has to be done before listing).
- M22: Release SD card.
Do all this in one chunk, splitting this up wouldn't allow to test
the result.
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.
For now this is just a nice demonstration on how to send bytes
over SPI. Add SD_CARD_SELECT_PIN to your configuration board
file manually to see data signals on MOSI dancing on the scope.
The TODO's about SS in arduino*.h were wrong, SS does have a
chip-specific special meaning (used in SPI multi-master or SPI
slave mode). Still, a #define MAX6675_SELECT_PIN is missing.
Squashed in this commit from the SPI development topic branch to
get this first step working:
Author: jbernardis <jeff.bernardis@gmail.com>
2015-02-04 22:35:07
mendel.c: disable SPI in power management only when not needed.
If we want to talk to a SD card connected to SPI, we need SPI
powered, of course.
From Traumflug: nice catch, Jeff!
Markus Hitter
Michael Moon