Simon suggested I open a new topic for this. I am trying to convert the sound recorder cookbook code to record to an internal filing system file for later re-use. I havn't yet been able to find a variable type which will allow the calls which use the file pointer to compile. The problem is that the sub-routines using the pointer come before it is created in the fopen command. If you swap the order round - putting main() first, then the calls to the subroutines wont compile.

Tony

Code here:

/* afa 3 Sep 20009 - uses sound recorder code to write to a local file */ #include <stdint.h> #include "mbed.h" DigitalOut l1(LED1); DigitalOut l2(LED2); DigitalOut l3(LED3); DigitalOut l4(LED4); AnalogIn ain(p20); Ticker ticker; Timer t; LocalFileSystem local("local"); int * fp; // have tried several different variable types here - none work /* Sampling routine; records a single sample */ void sample() { static const float ALPHA = 0.999f; static float v; float l, s = ain.read(); /* Convert raw value to sample */ int8_t b = (s - 0.5f) * 127.0f * 2.0f; /* Compute next bar graph value */ l = abs(s - 0.5f) * 2.0; v = l > v ? l : v * ALPHA; /* Snazzy bar graph */ l1 = v > 0.08; l2 = v > 0.16; l3 = v > 0.32; l4 = v > 0.62; fprintf(fp, "%c", b); } /* Write a 32 bit value in correct byte order for SND files */ void write32(uint32_t v) { uint8_t *b = (uint8_t *)&v; fprintf(fp, "%c%c%c%c", b[3], b[2], b[1], b[0]); } int main() { FILE *fp = fopen("/local/out.snd", "w"); // Open "out.snd" on the local file system for writing /* Au format header: http://en.wikipedia.org/wiki/Au_file_format */ fprintf(fp, ".snd"); write32(24); write32(-1); write32(2); write32(8000); write32(1); /* Sampler */ ticker.attach(sample(fp), 1.0f / 8000.0f); t.start(); while(t.read < 10.0) { wait(1); } t.stop(); fclose(fp); }

Code properly formatted (ps how do you use this system?):
 
 /* afa 3 Sep 20009 - uses sound recorder code to write to a local file */

#include 
#include "mbed.h"

DigitalOut l1(LED1);
DigitalOut l2(LED2);
DigitalOut l3(LED3);
DigitalOut l4(LED4);
AnalogIn ain(p20);
Ticker ticker;
Timer t;
LocalFileSystem local("local");
int * fp; // have tried several different variable types here - none work

/* Sampling routine; records a single sample */
void sample()
{
    static const float ALPHA = 0.999f;
    static float v;
    float l, s =  ain.read();
    
    /* Convert raw value to sample */
    int8_t b = (s - 0.5f) * 127.0f * 2.0f;

    /* Compute next bar graph value */
    l = abs(s - 0.5f) * 2.0;
    v = l > v ? l : v * ALPHA;

    /* Snazzy bar graph */
    l1 = v > 0.08;
    l2 = v > 0.16;
    l3 = v > 0.32;
    l4 = v > 0.62;    

    fprintf(fp, "%c", b);
}

/* Write a 32 bit value in correct byte order for SND files */
void write32(uint32_t v)
{
    uint8_t *b = (uint8_t *)&v;
    
    fprintf(fp, "%c%c%c%c", b[3], b[2], b[1], b[0]);
}



int main() 
{
   
 FILE *fp = fopen("/local/out.snd", "w");  // Open "out.snd" on the local file system for writing   
    /* Au format header: http://en.wikipedia.org/wiki/Au_file_format */
    
    fprintf(fp, ".snd");
    write32(24);
    write32(-1);    
    write32(2);        
    write32(8000);        
    write32(1);        
    
    /* Sampler */
    ticker.attach(sample(fp), 1.0f / 8000.0f);
    t.start();
    while(t.read < 10.0) {
        wait(1);           
    }
    t.stop();
    fclose(fp);
   
    }

Hi Tony,

It looks like you are trying to create a "global" file pointer, so the basic code you are looking for is:

LocalFileSystem local("local");
FILE *fp; 

and then in main, as your file pointer is already defined, you'd just do:

int main() {
    fp = fopen("/local/out.snd", "w"); // open file, and store pointer in global FILE*

I expect this will do what you want.

As an aside, if you wanted to avoid a global FILE pointer, you could always pass the file pointer to your functions. Something like:

#include "mbed.h"

LocalFileSystem local("local");

void do_something_to_file(FILE *fp) {
    fprintf(fp, "Hello World\n");
}

int main() {
   FILE *p = fopen("/local/out.txt", "w");
   do_something_to_file(p);
}

Hope that helps!

Simon

Simon Ford wrote:
FILE *fp;

Thanks Simon - its the 'FILE' type I didn't know about. That works - now to fix the other errors ;-)

Tony