Create a tiny file system

Page last updated 21 Jan 2014, by Yihui Xiong. 0 replies

When you connect an mbed LPC11U24 with a computer, a disk named "MBED" will pop up. In the disk, there is a "MBED.HTM" file which will lead you to mbed.org.

I really like this feature. So when we design Arch, we use the Arch as a tiny disk to provide the feature. Implementing it takes three steps:

  1. Use USBMSD library to turn the Arch into a disk
  2. Create a tiny file system
  3. Put the file system into the Arch

Make a disk

It's quite easy to make a disk using USBMSD library. Here is a demo program. The content of the disk is in "DiskImage.c" file.

Import program
USBTinyDisk_Arch - main.cpp

00001 #include "mbed.h"
00002 #include "USBTinyDisk.h"
00003 
00004 BusOut leds(LED1, LED2, LED3, LED4);
00005 USBTinyDisk disk;
00006 
00007 int main() {
00008     disk.connect();
00009     
00010     uint8_t count = 0;
00011     while(1) {
00012         leds = count;
00013         count++;
00014         wait(1);
00015     }
00016 }

Create a custom file system

We can easily create a custom file system on linux.

git clone https://github.com/xiongyihui/dosfstools.git
cd dosfstools
make
dd if=/dev/zero of=disk bs=1024 count=2
./mkfs.fat -a -n "name" -s 1 -S 512 -f 1 -h 0 -F 12 -r 16 -R 1 disk
mkdir mnt
sudo mount disk mnt
sudo echo "hello, mbed" > mnt/README.txt"
sudo umount mnt
python b2c.py disk DiskImage.c

The file system is in DiskImage.c. Use it in the above program, you will get the custom tiny disk.

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