Get an mbed!
Subscribe to the mailing list
A library to allow SD Cards to be accessed as a filesystem, using a SPI interface.
00001 // example writing to SD card, sford 00002 00003 #include "mbed.h" 00004 #include "SDFileSystem.h" 00005 00006 SDFileSystem sd(p5, p6, p7, p8, "sd"); // the pinout on the mbed Cool Components workshop board 00007 00008 int main() { 00009 printf("Hello World!\n"); 00010 00011 mkdir("/sd/mydir", 0777); 00012 00013 FILE *fp = fopen("/sd/mydir/sdtest.txt", "w"); 00014 if(fp == NULL) { 00015 error("Could not open file for write\n"); 00016 } 00017 fprintf(fp, "Hello fun SD Card World!"); 00018 fclose(fp); 00019 00020 printf("Goodbye World!\n"); 00021 }
The SDFileSystem library, for accessing SD Cards using fopen, fprintf, etc.
SD Cards are widely used by loads of devices for storage; phones, mp3 players, pc's etc. That means they are a very cheap option for storing large amounts of non-volatile data (i.e. the data is not lost when the power is removed). They should be ideal for data logging and storing audio/images.
SD and MMC cards support various protocols, but common to them all is one based on SPI. This is the one used here as, whilst not being the most high performance, it uses a generic SPI interface so will be more portable.
SD Cards are block devices. That means you read/write data in multiples of the block size (usually 512-bytes); the interface is basically "read from block address n", "write to block address m". Note that a filesystem (e.g. FAT) is an abstraction on top of this, and the disk itself knows nothing about the filesystem.
Based on a SparkFun MicroSD Breakout Board, here is the wiring that will work (you can obviously use either SPI port, and any DigitalOut):
SparkFun MicroSD Breakout Board MicroSD Breakout mbed CS o-------------o 8 (DigitalOut cs) DI o-------------o 5 (SPI mosi) VCC o-------------o VOUT SCK o-------------o 7 (SPI sclk) GND o-------------o GND DO o-------------o 6 (SPI miso) CD o
Hi All,
I am experiencing a weird phenomenon. I am running the SD card Hello world tutorial by Simon Ford. Using a freshly formatted 256MB SD Card the program runs smoothly with no errors. If I reset the mBed (using the reset switch) the program will run smooth again. If I repeat this process another 10 times (ish), the program then stops working and exhibits the blue lights of death. The serial out the messages back 'No disk, or could not put SD card in to SPI idle state'. This message continues to appear until the card is reformatted. Before formating I have noticed that there are some weird files saved to the SD card. I don't know where theses are coming from. I can only assume it is something to do with my hardware, perhaps interference. I am using a bread board. I intended to transfer on to strip board. I am posting this just in case someone else has seen this and can advise how I can fix this issue. Thanks.
HM Yoong wrote: From the SDFileSystem.cpp file, I do not know how standard C buffered I/O functions such as fprintf(), fread(), fwrite() call the member functions in SDFileSystem. My questions:
a) How big is the buffer can be allocated by user? Any guide? b) Can I use unbuffered I/O function such as read, write, seek?
I am thinking to use the library to stored large files in SD card for data logging purposes. As data logging only insert at the end, so we may be able to improve performance without the buffering abstraction.
Any idea? Thank
I found the answers and get a solution from http://mbed.org/users/emh203/notebook/long-file-name-example-code/
Goran Jurkovic wrote: Is there a workaround for microSD cards larger than 2GB?
dowload SDHCFileSystem library
http://mbed.org/users/xxll/programs/SDHCFileSystem/5zdtq
I now work with a 8Go sd card
Please login to post comments.
Wiki home
Recent changes
All Pages
New Page
Slingshot user guide 
Page history
I am using a cool components mbed workshop breakout board modified your latest SDcardtest as shown for cool components mbed workshop breakout board
SDFileSystem sd(p11, p12, p13, p27, "sd"); SDFileSystem sd(p5, p6, p7, p8, "sd"); my cool components mbed workshop breakout board
Target is Fuji 2Gb from RS components 375-953 less than £10 inc vat with SD adapter works straight out of the box well done. I just checked that it was Fat 16 when delivered, it was.