RE: How to read the file with f_read() function - USB Mass Storage class module

bojan — Thu, 16 May 2019 10:47:59 GMT

By exploring this site I found more about FatFS.

One way to reading a file would be to open it first with f_open() function by knowing the name of the file in advance.

            FRESULT fr;            
            FIL file; 
            uint16_t size;
            UINT bytesRead;

            fr = f_open(&file, "eyes2.bmp", FA_READ);

            if (fr == FR_OK){
                NRF_LOG_INFO("File eyes2.bmp sucessfully opened!");
                size = f_size(&file);
                char * data = NULL;

                data = malloc(size); /* allocate memory to store image data */
                NRF_LOG_INFO("File size: %d bytes", size);

                fr = f_read(&file, data, (UINT) size, &bytesRead);
                if (fr == FR_OK){
                    NRF_LOG_INFO("File successfully read!");
                    NRF_LOG_INFO("%d bytes read", bytesRead);
                    for (int i=0; i < bytesRead; i++)
                    {
                        NRF_LOG_INFO("data[%d]: 0x%x", i, data[i]);
                    }
                }
                free(data); // free allocated memory when you don't need it

                f_close(&file);
            }

In the code above, I know there is a file called "eyes2.bmp" and I was able to open it and read it. What if I don't know the name of the file (the user can drop the files in folder from PC and the code should be able to read the files without having any idea about the file name)?

Should I list the directory first with fatfs_ls() to find out how many files are there and after that open the particular file from the list (e.g. 5th file from the list of 10 files available in the folder)?

Thanks once again.

Cheers,

Bojan.