| =============================== |
| Linux Gadget Serial Driver v2.0 |
| =============================== |
| |
| 11/20/2004 |
| |
| (updated 8-May-2008 for v2.3) |
| |
| |
| License and Disclaimer |
| ---------------------- |
| This program is free software; you can redistribute it and/or |
| modify it under the terms of the GNU General Public License as |
| published by the Free Software Foundation; either version 2 of |
| the License, or (at your option) any later version. |
| |
| This program is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| GNU General Public License for more details. |
| |
| You should have received a copy of the GNU General Public |
| License along with this program; if not, write to the Free |
| Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, |
| MA 02111-1307 USA. |
| |
| This document and the gadget serial driver itself are |
| Copyright (C) 2004 by Al Borchers (alborchers@steinerpoint.com). |
| |
| If you have questions, problems, or suggestions for this driver |
| please contact Al Borchers at alborchers@steinerpoint.com. |
| |
| |
| Prerequisites |
| ------------- |
| Versions of the gadget serial driver are available for the |
| 2.4 Linux kernels, but this document assumes you are using |
| version 2.3 or later of the gadget serial driver in a 2.6 |
| Linux kernel. |
| |
| This document assumes that you are familiar with Linux and |
| Windows and know how to configure and build Linux kernels, run |
| standard utilities, use minicom and HyperTerminal, and work with |
| USB and serial devices. It also assumes you configure the Linux |
| gadget and usb drivers as modules. |
| |
| With version 2.3 of the driver, major and minor device nodes are |
| no longer statically defined. Your Linux based system should mount |
| sysfs in /sys, and use "mdev" (in Busybox) or "udev" to make the |
| /dev nodes matching the sysfs /sys/class/tty files. |
| |
| |
| |
| Overview |
| -------- |
| The gadget serial driver is a Linux USB gadget driver, a USB device |
| side driver. It runs on a Linux system that has USB device side |
| hardware; for example, a PDA, an embedded Linux system, or a PC |
| with a USB development card. |
| |
| The gadget serial driver talks over USB to either a CDC ACM driver |
| or a generic USB serial driver running on a host PC:: |
| |
| Host |
| -------------------------------------- |
| | Host-Side CDC ACM USB Host | |
| | Operating | or | Controller | USB |
| | System | Generic USB | Driver |-------- |
| | (Linux or | Serial | and | | |
| | Windows) Driver USB Stack | | |
| -------------------------------------- | |
| | |
| | |
| | |
| Gadget | |
| -------------------------------------- | |
| | Gadget USB Periph. | | |
| | Device-Side | Gadget | Controller | | |
| | Linux | Serial | Driver |-------- |
| | Operating | Driver | and | |
| | System USB Stack | |
| -------------------------------------- |
| |
| On the device-side Linux system, the gadget serial driver looks |
| like a serial device. |
| |
| On the host-side system, the gadget serial device looks like a |
| CDC ACM compliant class device or a simple vendor specific device |
| with bulk in and bulk out endpoints, and it is treated similarly |
| to other serial devices. |
| |
| The host side driver can potentially be any ACM compliant driver |
| or any driver that can talk to a device with a simple bulk in/out |
| interface. Gadget serial has been tested with the Linux ACM driver, |
| the Windows usbser.sys ACM driver, and the Linux USB generic serial |
| driver. |
| |
| With the gadget serial driver and the host side ACM or generic |
| serial driver running, you should be able to communicate between |
| the host and the gadget side systems as if they were connected by a |
| serial cable. |
| |
| The gadget serial driver only provides simple unreliable data |
| communication. It does not yet handle flow control or many other |
| features of normal serial devices. |
| |
| |
| Installing the Gadget Serial Driver |
| ----------------------------------- |
| To use the gadget serial driver you must configure the Linux gadget |
| side kernel for "Support for USB Gadgets", for a "USB Peripheral |
| Controller" (for example, net2280), and for the "Serial Gadget" |
| driver. All this are listed under "USB Gadget Support" when |
| configuring the kernel. Then rebuild and install the kernel or |
| modules. |
| |
| Then you must load the gadget serial driver. To load it as an |
| ACM device (recommended for interoperability), do this:: |
| |
| modprobe g_serial |
| |
| To load it as a vendor specific bulk in/out device, do this:: |
| |
| modprobe g_serial use_acm=0 |
| |
| This will also automatically load the underlying gadget peripheral |
| controller driver. This must be done each time you reboot the gadget |
| side Linux system. You can add this to the start up scripts, if |
| desired. |
| |
| Your system should use mdev (from busybox) or udev to make the |
| device nodes. After this gadget driver has been set up you should |
| then see a /dev/ttyGS0 node:: |
| |
| # ls -l /dev/ttyGS0 | cat |
| crw-rw---- 1 root root 253, 0 May 8 14:10 /dev/ttyGS0 |
| # |
| |
| Note that the major number (253, above) is system-specific. If |
| you need to create /dev nodes by hand, the right numbers to use |
| will be in the /sys/class/tty/ttyGS0/dev file. |
| |
| When you link this gadget driver early, perhaps even statically, |
| you may want to set up an /etc/inittab entry to run "getty" on it. |
| The /dev/ttyGS0 line should work like most any other serial port. |
| |
| |
| If gadget serial is loaded as an ACM device you will want to use |
| either the Windows or Linux ACM driver on the host side. If gadget |
| serial is loaded as a bulk in/out device, you will want to use the |
| Linux generic serial driver on the host side. Follow the appropriate |
| instructions below to install the host side driver. |
| |
| |
| Installing the Windows Host ACM Driver |
| -------------------------------------- |
| To use the Windows ACM driver you must have the "linux-cdc-acm.inf" |
| file (provided along this document) which supports all recent versions |
| of Windows. |
| |
| When the gadget serial driver is loaded and the USB device connected |
| to the Windows host with a USB cable, Windows should recognize the |
| gadget serial device and ask for a driver. Tell Windows to find the |
| driver in the folder that contains the "linux-cdc-acm.inf" file. |
| |
| For example, on Windows XP, when the gadget serial device is first |
| plugged in, the "Found New Hardware Wizard" starts up. Select |
| "Install from a list or specific location (Advanced)", then on the |
| next screen select "Include this location in the search" and enter the |
| path or browse to the folder containing the "linux-cdc-acm.inf" file. |
| Windows will complain that the Gadget Serial driver has not passed |
| Windows Logo testing, but select "Continue anyway" and finish the |
| driver installation. |
| |
| On Windows XP, in the "Device Manager" (under "Control Panel", |
| "System", "Hardware") expand the "Ports (COM & LPT)" entry and you |
| should see "Gadget Serial" listed as the driver for one of the COM |
| ports. |
| |
| To uninstall the Windows XP driver for "Gadget Serial", right click |
| on the "Gadget Serial" entry in the "Device Manager" and select |
| "Uninstall". |
| |
| |
| Installing the Linux Host ACM Driver |
| ------------------------------------ |
| To use the Linux ACM driver you must configure the Linux host side |
| kernel for "Support for Host-side USB" and for "USB Modem (CDC ACM) |
| support". |
| |
| Once the gadget serial driver is loaded and the USB device connected |
| to the Linux host with a USB cable, the host system should recognize |
| the gadget serial device. For example, the command:: |
| |
| cat /sys/kernel/debug/usb/devices |
| |
| should show something like this::: |
| |
| T: Bus=01 Lev=01 Prnt=01 Port=01 Cnt=02 Dev#= 5 Spd=480 MxCh= 0 |
| D: Ver= 2.00 Cls=02(comm.) Sub=00 Prot=00 MxPS=64 #Cfgs= 1 |
| P: Vendor=0525 ProdID=a4a7 Rev= 2.01 |
| S: Manufacturer=Linux 2.6.8.1 with net2280 |
| S: Product=Gadget Serial |
| S: SerialNumber=0 |
| C:* #Ifs= 2 Cfg#= 2 Atr=c0 MxPwr= 2mA |
| I: If#= 0 Alt= 0 #EPs= 1 Cls=02(comm.) Sub=02 Prot=01 Driver=acm |
| E: Ad=83(I) Atr=03(Int.) MxPS= 8 Ivl=32ms |
| I: If#= 1 Alt= 0 #EPs= 2 Cls=0a(data ) Sub=00 Prot=00 Driver=acm |
| E: Ad=81(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms |
| E: Ad=02(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms |
| |
| If the host side Linux system is configured properly, the ACM driver |
| should be loaded automatically. The command "lsmod" should show the |
| "acm" module is loaded. |
| |
| |
| Installing the Linux Host Generic USB Serial Driver |
| --------------------------------------------------- |
| To use the Linux generic USB serial driver you must configure the |
| Linux host side kernel for "Support for Host-side USB", for "USB |
| Serial Converter support", and for the "USB Generic Serial Driver". |
| |
| Once the gadget serial driver is loaded and the USB device connected |
| to the Linux host with a USB cable, the host system should recognize |
| the gadget serial device. For example, the command:: |
| |
| cat /sys/kernel/debug/usb/devices |
| |
| should show something like this::: |
| |
| T: Bus=01 Lev=01 Prnt=01 Port=01 Cnt=02 Dev#= 6 Spd=480 MxCh= 0 |
| D: Ver= 2.00 Cls=ff(vend.) Sub=00 Prot=00 MxPS=64 #Cfgs= 1 |
| P: Vendor=0525 ProdID=a4a6 Rev= 2.01 |
| S: Manufacturer=Linux 2.6.8.1 with net2280 |
| S: Product=Gadget Serial |
| S: SerialNumber=0 |
| C:* #Ifs= 1 Cfg#= 1 Atr=c0 MxPwr= 2mA |
| I: If#= 0 Alt= 0 #EPs= 2 Cls=0a(data ) Sub=00 Prot=00 Driver=serial |
| E: Ad=81(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms |
| E: Ad=02(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms |
| |
| You must load the usbserial driver and explicitly set its parameters |
| to configure it to recognize the gadget serial device, like this:: |
| |
| echo 0x0525 0xA4A6 >/sys/bus/usb-serial/drivers/generic/new_id |
| |
| The legacy way is to use module parameters:: |
| |
| modprobe usbserial vendor=0x0525 product=0xA4A6 |
| |
| If everything is working, usbserial will print a message in the |
| system log saying something like "Gadget Serial converter now |
| attached to ttyUSB0". |
| |
| |
| Testing with Minicom or HyperTerminal |
| ------------------------------------- |
| Once the gadget serial driver and the host driver are both installed, |
| and a USB cable connects the gadget device to the host, you should |
| be able to communicate over USB between the gadget and host systems. |
| You can use minicom or HyperTerminal to try this out. |
| |
| On the gadget side run "minicom -s" to configure a new minicom |
| session. Under "Serial port setup" set "/dev/ttygserial" as the |
| "Serial Device". Set baud rate, data bits, parity, and stop bits, |
| to 9600, 8, none, and 1--these settings mostly do not matter. |
| Under "Modem and dialing" erase all the modem and dialing strings. |
| |
| On a Linux host running the ACM driver, configure minicom similarly |
| but use "/dev/ttyACM0" as the "Serial Device". (If you have other |
| ACM devices connected, change the device name appropriately.) |
| |
| On a Linux host running the USB generic serial driver, configure |
| minicom similarly, but use "/dev/ttyUSB0" as the "Serial Device". |
| (If you have other USB serial devices connected, change the device |
| name appropriately.) |
| |
| On a Windows host configure a new HyperTerminal session to use the |
| COM port assigned to Gadget Serial. The "Port Settings" will be |
| set automatically when HyperTerminal connects to the gadget serial |
| device, so you can leave them set to the default values--these |
| settings mostly do not matter. |
| |
| With minicom configured and running on the gadget side and with |
| minicom or HyperTerminal configured and running on the host side, |
| you should be able to send data back and forth between the gadget |
| side and host side systems. Anything you type on the terminal |
| window on the gadget side should appear in the terminal window on |
| the host side and vice versa. |
