Root/Documentation/usb/gadget_serial.txt

1
2                 Linux Gadget Serial Driver v2.0
3                           11/20/2004
4                  (updated 8-May-2008 for v2.3)
5
6
7License and Disclaimer
8----------------------
9This program is free software; you can redistribute it and/or
10modify it under the terms of the GNU General Public License as
11published by the Free Software Foundation; either version 2 of
12the License, or (at your option) any later version.
13
14This program is distributed in the hope that it will be useful,
15but WITHOUT ANY WARRANTY; without even the implied warranty of
16MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17GNU General Public License for more details.
18
19You should have received a copy of the GNU General Public
20License along with this program; if not, write to the Free
21Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
22MA 02111-1307 USA.
23
24This document and the gadget serial driver itself are
25Copyright (C) 2004 by Al Borchers (alborchers@steinerpoint.com).
26
27If you have questions, problems, or suggestions for this driver
28please contact Al Borchers at alborchers@steinerpoint.com.
29
30
31Prerequisites
32-------------
33Versions of the gadget serial driver are available for the
342.4 Linux kernels, but this document assumes you are using
35version 2.3 or later of the gadget serial driver in a 2.6
36Linux kernel.
37
38This document assumes that you are familiar with Linux and
39Windows and know how to configure and build Linux kernels, run
40standard utilities, use minicom and HyperTerminal, and work with
41USB and serial devices. It also assumes you configure the Linux
42gadget and usb drivers as modules.
43
44With version 2.3 of the driver, major and minor device nodes are
45no longer statically defined. Your Linux based system should mount
46sysfs in /sys, and use "mdev" (in Busybox) or "udev" to make the
47/dev nodes matching the sysfs /sys/class/tty files.
48
49
50
51Overview
52--------
53The gadget serial driver is a Linux USB gadget driver, a USB device
54side driver. It runs on a Linux system that has USB device side
55hardware; for example, a PDA, an embedded Linux system, or a PC
56with a USB development card.
57
58The gadget serial driver talks over USB to either a CDC ACM driver
59or a generic USB serial driver running on a host PC.
60
61   Host
62   --------------------------------------
63  | Host-Side CDC ACM USB Host |
64  | Operating | or | Controller | USB
65  | System | Generic USB | Driver |--------
66  | (Linux or | Serial | and | |
67  | Windows) Driver USB Stack | |
68   -------------------------------------- |
69                                                  |
70                                                  |
71                                                  |
72   Gadget |
73   -------------------------------------- |
74  | Gadget USB Periph. | |
75  | Device-Side | Gadget | Controller | |
76  | Linux | Serial | Driver |--------
77  | Operating | Driver | and |
78  | System USB Stack |
79   --------------------------------------
80
81On the device-side Linux system, the gadget serial driver looks
82like a serial device.
83
84On the host-side system, the gadget serial device looks like a
85CDC ACM compliant class device or a simple vendor specific device
86with bulk in and bulk out endpoints, and it is treated similarly
87to other serial devices.
88
89The host side driver can potentially be any ACM compliant driver
90or any driver that can talk to a device with a simple bulk in/out
91interface. Gadget serial has been tested with the Linux ACM driver,
92the Windows usbser.sys ACM driver, and the Linux USB generic serial
93driver.
94
95With the gadget serial driver and the host side ACM or generic
96serial driver running, you should be able to communicate between
97the host and the gadget side systems as if they were connected by a
98serial cable.
99
100The gadget serial driver only provides simple unreliable data
101communication. It does not yet handle flow control or many other
102features of normal serial devices.
103
104
105Installing the Gadget Serial Driver
106-----------------------------------
107To use the gadget serial driver you must configure the Linux gadget
108side kernel for "Support for USB Gadgets", for a "USB Peripheral
109Controller" (for example, net2280), and for the "Serial Gadget"
110driver. All this are listed under "USB Gadget Support" when
111configuring the kernel. Then rebuild and install the kernel or
112modules.
113
114Then you must load the gadget serial driver. To load it as an
115ACM device (recommended for interoperability), do this:
116
117  modprobe g_serial
118
119To load it as a vendor specific bulk in/out device, do this:
120
121  modprobe g_serial use_acm=0
122
123This will also automatically load the underlying gadget peripheral
124controller driver. This must be done each time you reboot the gadget
125side Linux system. You can add this to the start up scripts, if
126desired.
127
128Your system should use mdev (from busybox) or udev to make the
129device nodes. After this gadget driver has been set up you should
130then see a /dev/ttyGS0 node:
131
132  # ls -l /dev/ttyGS0 | cat
133  crw-rw---- 1 root root 253, 0 May 8 14:10 /dev/ttyGS0
134  #
135
136Note that the major number (253, above) is system-specific. If
137you need to create /dev nodes by hand, the right numbers to use
138will be in the /sys/class/tty/ttyGS0/dev file.
139
140When you link this gadget driver early, perhaps even statically,
141you may want to set up an /etc/inittab entry to run "getty" on it.
142The /dev/ttyGS0 line should work like most any other serial port.
143
144
145If gadget serial is loaded as an ACM device you will want to use
146either the Windows or Linux ACM driver on the host side. If gadget
147serial is loaded as a bulk in/out device, you will want to use the
148Linux generic serial driver on the host side. Follow the appropriate
149instructions below to install the host side driver.
150
151
152Installing the Windows Host ACM Driver
153--------------------------------------
154To use the Windows ACM driver you must have the files "gserial.inf"
155and "usbser.sys" together in a folder on the Windows machine.
156
157The "gserial.inf" file is given here.
158
159-------------------- CUT HERE --------------------
160[Version]
161Signature="$Windows NT$"
162Class=Ports
163ClassGuid={4D36E978-E325-11CE-BFC1-08002BE10318}
164Provider=%LINUX%
165DriverVer=08/17/2004,0.0.2.0
166; Copyright (C) 2004 Al Borchers (alborchers@steinerpoint.com)
167
168[Manufacturer]
169%LINUX%=GSerialDeviceList
170
171[GSerialDeviceList]
172%GSERIAL%=GSerialInstall, USB\VID_0525&PID_A4A7
173
174[DestinationDirs]
175DefaultDestDir=10,System32\Drivers
176
177[GSerialInstall]
178CopyFiles=GSerialCopyFiles
179AddReg=GSerialAddReg
180
181[GSerialCopyFiles]
182usbser.sys
183
184[GSerialAddReg]
185HKR,,DevLoader,,*ntkern
186HKR,,NTMPDriver,,usbser.sys
187HKR,,EnumPropPages32,,"MsPorts.dll,SerialPortPropPageProvider"
188
189[GSerialInstall.Services]
190AddService = usbser,0x0002,GSerialService
191
192[GSerialService]
193DisplayName = %GSERIAL_DISPLAY_NAME%
194ServiceType = 1 ; SERVICE_KERNEL_DRIVER
195StartType = 3 ; SERVICE_DEMAND_START
196ErrorControl = 1 ; SERVICE_ERROR_NORMAL
197ServiceBinary = %10%\System32\Drivers\usbser.sys
198LoadOrderGroup = Base
199
200[Strings]
201LINUX = "Linux"
202GSERIAL = "Gadget Serial"
203GSERIAL_DISPLAY_NAME = "USB Gadget Serial Driver"
204-------------------- CUT HERE --------------------
205
206The "usbser.sys" file comes with various versions of Windows.
207For example, it can be found on Windows XP typically in
208
209  C:\WINDOWS\Driver Cache\i386\driver.cab
210
211Or it can be found on the Windows 98SE CD in the "win98" folder
212in the "DRIVER11.CAB" through "DRIVER20.CAB" cab files. You will
213need the DOS "expand" program, the Cygwin "cabextract" program, or
214a similar program to unpack these cab files and extract "usbser.sys".
215
216For example, to extract "usbser.sys" into the current directory
217on Windows XP, open a DOS window and run a command like
218
219  expand C:\WINDOWS\Driver~1\i386\driver.cab -F:usbser.sys .
220
221(Thanks to Nishant Kamat for pointing out this DOS command.)
222
223When the gadget serial driver is loaded and the USB device connected
224to the Windows host with a USB cable, Windows should recognize the
225gadget serial device and ask for a driver. Tell Windows to find the
226driver in the folder that contains "gserial.inf" and "usbser.sys".
227
228For example, on Windows XP, when the gadget serial device is first
229plugged in, the "Found New Hardware Wizard" starts up. Select
230"Install from a list or specific location (Advanced)", then on
231the next screen select "Include this location in the search" and
232enter the path or browse to the folder containing "gserial.inf" and
233"usbser.sys". Windows will complain that the Gadget Serial driver
234has not passed Windows Logo testing, but select "Continue anyway"
235and finish the driver installation.
236
237On Windows XP, in the "Device Manager" (under "Control Panel",
238"System", "Hardware") expand the "Ports (COM & LPT)" entry and you
239should see "Gadget Serial" listed as the driver for one of the COM
240ports.
241
242To uninstall the Windows XP driver for "Gadget Serial", right click
243on the "Gadget Serial" entry in the "Device Manager" and select
244"Uninstall".
245
246
247Installing the Linux Host ACM Driver
248------------------------------------
249To use the Linux ACM driver you must configure the Linux host side
250kernel for "Support for Host-side USB" and for "USB Modem (CDC ACM)
251support".
252
253Once the gadget serial driver is loaded and the USB device connected
254to the Linux host with a USB cable, the host system should recognize
255the gadget serial device. For example, the command
256
257  cat /proc/bus/usb/devices
258
259should show something like this:
260
261T: Bus=01 Lev=01 Prnt=01 Port=01 Cnt=02 Dev#= 5 Spd=480 MxCh= 0
262D: Ver= 2.00 Cls=02(comm.) Sub=00 Prot=00 MxPS=64 #Cfgs= 1
263P: Vendor=0525 ProdID=a4a7 Rev= 2.01
264S: Manufacturer=Linux 2.6.8.1 with net2280
265S: Product=Gadget Serial
266S: SerialNumber=0
267C:* #Ifs= 2 Cfg#= 2 Atr=c0 MxPwr= 2mA
268I: If#= 0 Alt= 0 #EPs= 1 Cls=02(comm.) Sub=02 Prot=01 Driver=acm
269E: Ad=83(I) Atr=03(Int.) MxPS= 8 Ivl=32ms
270I: If#= 1 Alt= 0 #EPs= 2 Cls=0a(data ) Sub=00 Prot=00 Driver=acm
271E: Ad=81(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
272E: Ad=02(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms
273
274If the host side Linux system is configured properly, the ACM driver
275should be loaded automatically. The command "lsmod" should show the
276"acm" module is loaded.
277
278
279Installing the Linux Host Generic USB Serial Driver
280---------------------------------------------------
281To use the Linux generic USB serial driver you must configure the
282Linux host side kernel for "Support for Host-side USB", for "USB
283Serial Converter support", and for the "USB Generic Serial Driver".
284
285Once the gadget serial driver is loaded and the USB device connected
286to the Linux host with a USB cable, the host system should recognize
287the gadget serial device. For example, the command
288
289  cat /proc/bus/usb/devices
290
291should show something like this:
292
293T: Bus=01 Lev=01 Prnt=01 Port=01 Cnt=02 Dev#= 6 Spd=480 MxCh= 0
294D: Ver= 2.00 Cls=ff(vend.) Sub=00 Prot=00 MxPS=64 #Cfgs= 1
295P: Vendor=0525 ProdID=a4a6 Rev= 2.01
296S: Manufacturer=Linux 2.6.8.1 with net2280
297S: Product=Gadget Serial
298S: SerialNumber=0
299C:* #Ifs= 1 Cfg#= 1 Atr=c0 MxPwr= 2mA
300I: If#= 0 Alt= 0 #EPs= 2 Cls=0a(data ) Sub=00 Prot=00 Driver=serial
301E: Ad=81(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
302E: Ad=02(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms
303
304You must explicitly load the usbserial driver with parameters to
305configure it to recognize the gadget serial device, like this:
306
307  modprobe usbserial vendor=0x0525 product=0xA4A6
308
309If everything is working, usbserial will print a message in the
310system log saying something like "Gadget Serial converter now
311attached to ttyUSB0".
312
313
314Testing with Minicom or HyperTerminal
315-------------------------------------
316Once the gadget serial driver and the host driver are both installed,
317and a USB cable connects the gadget device to the host, you should
318be able to communicate over USB between the gadget and host systems.
319You can use minicom or HyperTerminal to try this out.
320
321On the gadget side run "minicom -s" to configure a new minicom
322session. Under "Serial port setup" set "/dev/ttygserial" as the
323"Serial Device". Set baud rate, data bits, parity, and stop bits,
324to 9600, 8, none, and 1--these settings mostly do not matter.
325Under "Modem and dialing" erase all the modem and dialing strings.
326
327On a Linux host running the ACM driver, configure minicom similarly
328but use "/dev/ttyACM0" as the "Serial Device". (If you have other
329ACM devices connected, change the device name appropriately.)
330
331On a Linux host running the USB generic serial driver, configure
332minicom similarly, but use "/dev/ttyUSB0" as the "Serial Device".
333(If you have other USB serial devices connected, change the device
334name appropriately.)
335
336On a Windows host configure a new HyperTerminal session to use the
337COM port assigned to Gadget Serial. The "Port Settings" will be
338set automatically when HyperTerminal connects to the gadget serial
339device, so you can leave them set to the default values--these
340settings mostly do not matter.
341
342With minicom configured and running on the gadget side and with
343minicom or HyperTerminal configured and running on the host side,
344you should be able to send data back and forth between the gadget
345side and host side systems. Anything you type on the terminal
346window on the gadget side should appear in the terminal window on
347the host side and vice versa.
348
349
350

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