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SD card: change demo code for performance measurement. 

As we're around here, lets see how fast this implementation is.
All measurements are raw reading performance, without actual
parsing of the G-code.

With SPI_2X disabled (see line 8 in spi.h), performance is
195 seconds per megabyte, equivalent to about 50'000 baud.

With SPI_2X enabled, performance is 159 seconds per megabyte,
or 60'000 baud.

Still, SPI_2X is left disabled to increase reliability. Reading
from SD is faster by design, because there is no checksumming and
also no waiting for the "ok" to be sent back. In case reading
G-code from SD ever becomes a bottleneck, there are even more
opportunities in addition to enabling SPI_2X, like making sdbuffer
bigger, like micro-optimizing spi_rw() and similar stuff.
This commit is contained in:
Markus Hitter 2015-07-02 19:21:47 +02:00
parent d3f548a895
commit c7b134bc65
1 changed files with 5 additions and 10 deletions
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15
mendel.c
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@ -279,18 +279,13 @@ int main (void)
}
#ifdef SD
#include "delay.h"
if (gcode_sources & GCODE_SOURCE_SD) {
c = sd_read_char();
/* Demo code here again, just write the character to the serial line,
leading to the file written as-is to there. This may help
demonstrating correctness of the implementation. */
if (c != 0) {
serial_writechar(c);
delay_us(1000);
}
else {
/* Demo code: just read all the bytes without doing anything with
them to allow measuring how long it takes to read a file. Report
over serial when the file is done. */
if (c == 0) {
serial_writestr_P(PSTR("\nSD file done.\n"));
gcode_sources &= ! GCODE_SOURCE_SD;
// There is no pf_close(), subsequent reads will stick at EOF
// and return zeros.