You need to plugin the USB, and read the doc and code.

Dependencies:   USBHost mbed

Fork of USBHostMSD_HelloWorld by Samuel Mokrani

Revision:
3:17ca010bda2e
Parent:
1:473f339c54c1
Child:
5:fc580cab6a61
diff -r 3e3df7a79050 -r 17ca010bda2e USBHost.lib
--- a/USBHost.lib	Tue Mar 12 17:35:32 2013 +0000
+++ b/USBHost.lib	Wed Mar 13 10:28:43 2013 +0000
@@ -1,1 +1,1 @@
-https://mbed.org/users/mbed_official/code/USBHost/#b320d68e98e7
+https://mbed.org/users/mbed_official/code/USBHost/#e48791a1ef18