Difference between revisions of "USB Gadget"

Revision as of 22:45, 26 November 2007

Instructions to use the USB port of your Armadeus board to communicate with your PC

Introduction

You can connect your Armadeus board to a PC using its USB port and it can be enumerated as many USB devices (depending on the type of communication way you want to use):

• serial device
• net device
• mass storage device

Installation

• configure your Linux kernel:

[armadeus]$ make linux-menuconfig

in Device Drivers->USB support->USB Gadget Support, choose:

File:Linuxconfig usb gadget.png

Support for USB Gadgets and activate all USB Gadget Drivers

• save your configuration and then rebuild your kernel image:

[armadeus]$ make

now you should have following drivers in your kernel source tree:

drivers/usb/gadget/gadgetfs.ko        For test
drivers/usb/gadget/g_ether.ko         Ethernet emulation on USB
drivers/usb/gadget/g_file_storage.ko  Mass storage
drivers/usb/gadget/g_serial.ko        Serial emulation on USB
drivers/usb/gadget/g_zero.ko          For test
drivers/usb/gadget/imx_udc.ko         i.MX USB device Core Controller 

Copy imx_udc.ko, g_file_storage.ko & g_serial.ko to your target root filessytem in /lib/modules/

Usage

First, load the core controller driver on your board:

# insmod /lib/modules/imx_udc.ko

To emulate a mass storage device:

• create or get a "backing storage file", for example: [[1]]
• copy this file (uncompressed) in the /tmp directory of your rootfs (see NetworkConfig if necessary)
• load g_file_storage module:

# insmod /lib/modules/g_file_storage.ko file=/tmp/backing_file

• connect target's USB cable to your PC and,

On Linux:

• as root, launch dmesg and find the /dev/sdaX device assigned to your board
• then mount the device and enjoy file sharing:

[root@toto]# mount /dev/sda1 /mnt/tmp
[root@toto]# cd /mnt/tmp
[root@toto]# showimage /mnt/tmp/test.jpg

To emulate a serial port:

# mknod /dev/ttygserial c 127 0   (only needed the first time you want to use it, if not already existing)
# insmod /lib/modules/g_serial.ko

TBDL

Links

• http://www.linux-usb.org/gadget/
• http://www.linux-usb.org/gadget/file_storage.html