5 years, 1 month ago.

write works, read fails

I am able to write the file using the example. But when I try to setup the file for read operation, it fails. I'm using an LPC11U24 target. If my flags on line 15 are "w", it works. Any ideas?

#include "mbed.h"
#include "SDFileSystem.h"
SDFileSystem sd(P1_22, P1_21, P1_20, P1_19, "sd"); // the pinout on the FT33 controller

Serial pc(P1_13, P1_14); // xbee port
int main() {
    int i;
    pc.printf("Hello World!\n");   
    mkdir("/sd/mydir", 0777);
    FILE *fp = fopen("/sd/mydir/sdtest.txt", "rw");
    if(fp == NULL) {
        pc.printf("Could not open file for read/write\n");
    else {
        pc.printf("Successfully opened file for read/write\n");
        pc.printf("Writing to card...\n");
        fprintf(fp, "Hello fun SD Card World!\r\n");
        for(i = 0; i < 25; i++) {
            fprintf(fp, "%d\r\n", i);
    pc.printf("Goodbye World!\n");

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