View source for USB Gadget Serial Driver

The USB Gadget Serial Driver provides a tty style serial line interface through the USB-OTG connection of the board.

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== General Information ==

For further information have a look at [http://www.kernel.org/doc/Documentation/usb/gadget_serial.txt http://www.kernel.org/doc/Documentation/usb/gadget_serial.txt].

== Configure the USB-OTG Port ==

To use USB Gadget features the USB-OTG Port has to be initialized in USB slave mode. Add <code>"otg_mode=device"</code> to the kernel commandline on the bootloader console.

On DHCOM boards it is possible to use the u-boot environment variable <code>"linux_add_param"</code>:
# enter bootloader console with DEL/BS Key
# <code>setenv linux_add_param otg_mode=device</code>
# <code>saveenv</code>


== Prepare the Kernel ==

Prepare the Linux Kernel Sources to be able to compile.

Open a console window and go to the root directory of the kernel sources and start the kernel configuration dialog:
* <code> ARCH=arm CROSS_COMPILE=arm-none-linux-gnueabi- make menuconfig </code>

Enable the following items:
* Device Drivers -->  USB Support -->  USB Gadget Support 
* Device Drivers -->  USB Support -->  USB Gadget Support --> USB Peripheral Controller 
:: choose the matching device controller:
::: * DHCOM AM35x: OMAP USB Device Controller
::: * DHCOM iMX25: Freescale Highspeed USB DR Peripheral Controller
* Device Drivers -->  USB Support -->  USB Gadget Support --> USB Gadget Drivers --> Serial Gadget (with CDC ACM and CDC OBEX support)

Exit the configuration dialog an start building the kernel:
* <code> ARCH=arm CROSS_COMPILE=arm-none-linux-gnueabi- make uImage </code>

Install the kernel on your board.


== Configure the Root Filesystem ==
To be able to do a user-login at the usb gadget serial line add the following line to <code>/etc/inittab</code> near line 65:

* <code> T1:23:respawn:/sbin/getty -L ttyGS0 9600 vt100 </code>

If you want to able to login as <code>"root"</code> you have to add <code>ttyGS0</code> to the file <code>/etc/securetty</code>.


== Host PC configuration ==

Connect the board via usb-otg to your host pc. If you working with linux search for <code>"/dev/ttyACM0"</code> or similar. You can open that device-file with minicom or similar tools without additional configurations.

If you want to connect to a windows host pc you have to install the required *.inf file before using the interface.
* [[media:usb_gadget_serial_inf.zip | Download *.inf file]]