File content as of revision 0:b179d330bb2e:

#include "mbed.h"
#include "SDFileSystem.h"
 
SDFileSystem sd(p5, p6, p7, p8, "sd"); // the pinout on the mbed Cool Components workshop board
DigitalIn enable(p30);
AnalogIn inpt(p20);
DigitalOut myled(LED1);
 
//float Log[16]={};
 
 Timer SDspeed;

void SD(int num, float btry, float time, float stack_time){
    myled = 1;
    
//    printf("Hello World!\n");   
 
    mkdir("/sd/mydir", 0777);

    
    SDspeed.start();
    
    FILE *fp_csv = fopen("/sd/mydir/SDtestSpeed.csv", "a");
    if(fp_csv == NULL) {
        error("Could not open file for write\n");
    }
    
    fprintf(fp_csv, "%d,%f,%.5f, %.5f\n", num, btry, time, stack_time);
    
    fclose(fp_csv); 
    
    SDspeed.stop();


    /////////////////
    
//    FILE *fp_txt = fopen("/sd/mydir/sdtest.txt", "a");
//    if(fp_txt == NULL) {
//        error("Could not open file for write\n");
//    }
//    fprintf(fp_txt, "Hello fun SD Card World!\n");
//    fprintf(fp_txt, "Hello fun SD Card World!\n");
//    fprintf(fp_txt, "%f,%f\n", btry, (float)num);
//    
//    fclose(fp_txt); 
    
    
    printf("Goodbye World!\n");
    myled = 0;
}
 
int main() {
    float btry_lg = 0;
    int nmbr_lg = 0;
    float wrt_SD_time = 0;
    float sec = 0;
    
    FILE *fp_csv = fopen("/sd/mydir/SDtestSpeed.csv", "w");
    if(fp_csv == NULL) {
        error("Could not open file for write\n");
    }
    fprintf(fp_csv, "number, battery, time\n");
    fclose(fp_csv); 
    
    while(1){
        // test the voltage on the initialized analog pin
        //  and if greater than 0.3 * VCC set the digital pin
        //  to a logic 1 otherwise a logic 0
        btry_lg = inpt.read()*3.3;
        
        //if(ain > 0.3f) {    
        //} else {
        //}
        
        // print the percentage and 16 bit normalized values
        //printf("percentage: %3.3f%%\n", ain.read()*100.0f);
        //printf("normalized: 0x%04X \n", ain.read_u16());
        //wait(0.2f);
        
        nmbr_lg++;
   
        SD(nmbr_lg, btry_lg, wrt_SD_time, sec);
        wrt_SD_time = SDspeed.read();
        sec += wrt_SD_time;
        
        wait_us(10);
    }
}