problem in write file or mkdir on android device

I have a android application which is write some html files on the 开发者_运维技巧sdcard.

The application run on emulator very well.

But when I tried to run the same application on OMAP android device It can't write files or mkdir on the device sdcard.

I don't know how it happened.

My OMAP device use sdcard for file system at the boot time thats why it is not taking the sdcard as a external storage device so "android.permission.WRITE_EXTERNAL_STORAGE" doesn't works.

now please help me to solve this problem.