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Newacct at 20:08, 11 February 2010

2010-02-11T20:08:53Z

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== Description ==

This example demonstrates how to read a file from the Micro-ROM (uROM) file system.

For the example to work, you'll need a sub-directory called data, containing the example.txt
example.txt should contain some text to be displayed, for example "Hello world!" or "Geez, it works!".

== Source Code ==
<source lang="c">
#include <dev/board.h>
#include <dev/urom.h>
#include <fs/uromfs.h>
#include <stdio.h>
#include <io.h>

/*
Include our uROM file
*/
#include "urom_data.c"

static char buff[256];

int main(void)
{
FILE *fp;

unsigned long baud = 115200;

NutRegisterDevice(&DEV_DEBUG, 0, 0);

freopen(DEV_DEBUG_NAME, "w", stdout);
_ioctl(_fileno(stdout), UART_SETSPEED, &baud);

puts("File read test\n");

if (NutRegisterDevice(&devUrom, 0, 0)) {
printf("UROM error\n");
}

fp = fopen("UROM:example.txt", "r");

while (!feof(fp)) {
fgets(buff, sizeof(buff), fp);
puts(buff);
}

fclose(fp);

for (;;);
}
</source>

You'll also need a slightly altered Makefile that creates your urom_data.c for you.

<source lang="c">
PROJ = urom_ex
DATADIR = data
DATAFILE = urom_data.c

include ../Makedefs

SRCS = $(PROJ).c
OBJS = $(SRCS:.c=.o)
LIBS = $(LIBDIR)/nutinit.o -lnutpro -lnutos -lnutnet -lnutfs -lnutcrt -lnutdev -lnutarch
TARG = $(PROJ).hex

all: $(DATAFILE) $(OBJS) $(TARG) $(ITARG) $(DTARG)

$(DATAFILE): $(DATADIR)/example.txt
$(CRUROM) -r -o$(DATAFILE) $(DATADIR)

include ../Makerules

clean:
-rm -f $(OBJS)
-rm -f $(TARG) $(ITARG) $(DTARG)
-rm -f $(DATAFILE)
</source>

== Details ==

<source lang="c">
char buff[256];
</source>

defines an array of the type char of 256 bytes. A char array is also called string.

<source lang="c">
unsigned long baud = 115200;

NutRegisterDevice(&DEV_DEBUG, 0, 0);

freopen(DEV_DEBUG_NAME, "w", stdout);
_ioctl(_fileno(stdout), UART_SETSPEED, &baud);

puts("File read test\n");
</source>

First, we set up our stdout device so we can print things to the terminal and output a line with "File read test!"

<source lang="c">
if (NutRegisterDevice(&devUrom, 0, 0)) {
printf("UROM error\n");
}
</source>

Here, we register the device driver for the uROM. Notice the difference in naming and capitalization between "DEV_DEBUG" and "devUrom".

<source lang="c">
fp = fopen("UROM:example.txt", "r");
</source>

We can open files from the uROM like any other files. Just prefix the filename with UROM: to tell Nut/OS that we're opening a file from uROM.

<source lang="c">
while (!feof(fp)) {
fgets(buff, sizeof(buff), fp);
puts(buff);
}
</source>

While we haven't reached the end of the file, we read a string into our buffer and print it to the terminal.
"fgets" reads a string from a file (strings end at the end of a line so we read the file one line at a time.) The "sizeof(buff)" restricts the amount of characters read to the length of our buffer. We don't want to read more than we can store.
"puts" then outputs the buffer to the terminal.

<source lang="c">
fclose(fp);
</source>

Don't forget to close the file after you're done with it.

== Output ==

File read test<br>
Hello world!

== See also ==
* [[Writing PHAT Files]]
* [[Reading PHAT Directories]]
* [[MMC MP3 Player]]
* More [[Nut/OS Examples]]

[[Category:Code Snippets]]

{{Languages}}

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Harald: 1 revision imported

Newacct at 20:08, 11 February 2010