1 =============================== 2 Linux Gadget Serial Driver v2.0 3 =============================== 4 5 11/20/2004 6 7 (updated 8-May-2008 for v2.3) 8 9 10 License and Disclaimer 11 ---------------------- 12 This program is free software; you can redistribute it and/or 13 modify it under the terms of the GNU General Public License as 14 published by the Free Software Foundation; either version 2 of 15 the License, or (at your option) any later version. 16 17 This program is distributed in the hope that it will be useful, 18 but WITHOUT ANY WARRANTY; without even the implied warranty of 19 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 20 GNU General Public License for more details. 21 22 You should have received a copy of the GNU General Public 23 License along with this program; if not, write to the Free 24 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, 25 MA 02111-1307 USA. 26 27 This document and the gadget serial driver itself are 28 Copyright (C) 2004 by Al Borchers (alborchers@steinerpoint.com). 29 30 If you have questions, problems, or suggestions for this driver 31 please contact Al Borchers at alborchers@steinerpoint.com. 32 33 34 Prerequisites 35 ------------- 36 Versions of the gadget serial driver are available for the 37 2.4 Linux kernels, but this document assumes you are using 38 version 2.3 or later of the gadget serial driver in a 2.6 39 Linux kernel. 40 41 This document assumes that you are familiar with Linux and 42 Windows and know how to configure and build Linux kernels, run 43 standard utilities, use minicom and HyperTerminal, and work with 44 USB and serial devices. It also assumes you configure the Linux 45 gadget and usb drivers as modules. 46 47 With version 2.3 of the driver, major and minor device nodes are 48 no longer statically defined. Your Linux based system should mount 49 sysfs in /sys, and use "mdev" (in Busybox) or "udev" to make the 50 /dev nodes matching the sysfs /sys/class/tty files. 51 52 53 54 Overview 55 -------- 56 The gadget serial driver is a Linux USB gadget driver, a USB device 57 side driver. It runs on a Linux system that has USB device side 58 hardware; for example, a PDA, an embedded Linux system, or a PC 59 with a USB development card. 60 61 The gadget serial driver talks over USB to either a CDC ACM driver 62 or a generic USB serial driver running on a host PC:: 63 64 Host 65 -------------------------------------- 66 | Host-Side CDC ACM USB Host | 67 | Operating | or | Controller | USB 68 | System | Generic USB | Driver |-------- 69 | (Linux or | Serial | and | | 70 | Windows) Driver USB Stack | | 71 -------------------------------------- | 72 | 73 | 74 | 75 Gadget | 76 -------------------------------------- | 77 | Gadget USB Periph. | | 78 | Device-Side | Gadget | Controller | | 79 | Linux | Serial | Driver |-------- 80 | Operating | Driver | and | 81 | System USB Stack | 82 -------------------------------------- 83 84 On the device-side Linux system, the gadget serial driver looks 85 like a serial device. 86 87 On the host-side system, the gadget serial device looks like a 88 CDC ACM compliant class device or a simple vendor specific device 89 with bulk in and bulk out endpoints, and it is treated similarly 90 to other serial devices. 91 92 The host side driver can potentially be any ACM compliant driver 93 or any driver that can talk to a device with a simple bulk in/out 94 interface. Gadget serial has been tested with the Linux ACM driver, 95 the Windows usbser.sys ACM driver, and the Linux USB generic serial 96 driver. 97 98 With the gadget serial driver and the host side ACM or generic 99 serial driver running, you should be able to communicate between 100 the host and the gadget side systems as if they were connected by a 101 serial cable. 102 103 The gadget serial driver only provides simple unreliable data 104 communication. It does not yet handle flow control or many other 105 features of normal serial devices. 106 107 108 Installing the Gadget Serial Driver 109 ----------------------------------- 110 To use the gadget serial driver you must configure the Linux gadget 111 side kernel for "Support for USB Gadgets", for a "USB Peripheral 112 Controller" (for example, net2280), and for the "Serial Gadget" 113 driver. All this are listed under "USB Gadget Support" when 114 configuring the kernel. Then rebuild and install the kernel or 115 modules. 116 117 Then you must load the gadget serial driver. To load it as an 118 ACM device (recommended for interoperability), do this:: 119 120 modprobe g_serial 121 122 To load it as a vendor specific bulk in/out device, do this:: 123 124 modprobe g_serial use_acm=0 125 126 This will also automatically load the underlying gadget peripheral 127 controller driver. This must be done each time you reboot the gadget 128 side Linux system. You can add this to the start up scripts, if 129 desired. 130 131 Your system should use mdev (from busybox) or udev to make the 132 device nodes. After this gadget driver has been set up you should 133 then see a /dev/ttyGS0 node:: 134 135 # ls -l /dev/ttyGS0 | cat 136 crw-rw---- 1 root root 253, 0 May 8 14:10 /dev/ttyGS0 137 # 138 139 Note that the major number (253, above) is system-specific. If 140 you need to create /dev nodes by hand, the right numbers to use 141 will be in the /sys/class/tty/ttyGS0/dev file. 142 143 When you link this gadget driver early, perhaps even statically, 144 you may want to set up an /etc/inittab entry to run "getty" on it. 145 The /dev/ttyGS0 line should work like most any other serial port. 146 147 148 If gadget serial is loaded as an ACM device you will want to use 149 either the Windows or Linux ACM driver on the host side. If gadget 150 serial is loaded as a bulk in/out device, you will want to use the 151 Linux generic serial driver on the host side. Follow the appropriate 152 instructions below to install the host side driver. 153 154 155 Installing the Windows Host ACM Driver 156 -------------------------------------- 157 To use the Windows ACM driver you must have the "linux-cdc-acm.inf" 158 file (provided along this document) which supports all recent versions 159 of Windows. 160 161 When the gadget serial driver is loaded and the USB device connected 162 to the Windows host with a USB cable, Windows should recognize the 163 gadget serial device and ask for a driver. Tell Windows to find the 164 driver in the folder that contains the "linux-cdc-acm.inf" file. 165 166 For example, on Windows XP, when the gadget serial device is first 167 plugged in, the "Found New Hardware Wizard" starts up. Select 168 "Install from a list or specific location (Advanced)", then on the 169 next screen select "Include this location in the search" and enter the 170 path or browse to the folder containing the "linux-cdc-acm.inf" file. 171 Windows will complain that the Gadget Serial driver has not passed 172 Windows Logo testing, but select "Continue anyway" and finish the 173 driver installation. 174 175 On Windows XP, in the "Device Manager" (under "Control Panel", 176 "System", "Hardware") expand the "Ports (COM & LPT)" entry and you 177 should see "Gadget Serial" listed as the driver for one of the COM 178 ports. 179 180 To uninstall the Windows XP driver for "Gadget Serial", right click 181 on the "Gadget Serial" entry in the "Device Manager" and select 182 "Uninstall". 183 184 185 Installing the Linux Host ACM Driver 186 ------------------------------------ 187 To use the Linux ACM driver you must configure the Linux host side 188 kernel for "Support for Host-side USB" and for "USB Modem (CDC ACM) 189 support". 190 191 Once the gadget serial driver is loaded and the USB device connected 192 to the Linux host with a USB cable, the host system should recognize 193 the gadget serial device. For example, the command:: 194 195 cat /sys/kernel/debug/usb/devices 196 197 should show something like this::: 198 199 T: Bus=01 Lev=01 Prnt=01 Port=01 Cnt=02 Dev#= 5 Spd=480 MxCh= 0 200 D: Ver= 2.00 Cls=02(comm.) Sub=00 Prot=00 MxPS=64 #Cfgs= 1 201 P: Vendor=0525 ProdID=a4a7 Rev= 2.01 202 S: Manufacturer=Linux 2.6.8.1 with net2280 203 S: Product=Gadget Serial 204 S: SerialNumber=0 205 C:* #Ifs= 2 Cfg#= 2 Atr=c0 MxPwr= 2mA 206 I: If#= 0 Alt= 0 #EPs= 1 Cls=02(comm.) Sub=02 Prot=01 Driver=acm 207 E: Ad=83(I) Atr=03(Int.) MxPS= 8 Ivl=32ms 208 I: If#= 1 Alt= 0 #EPs= 2 Cls=0a(data ) Sub=00 Prot=00 Driver=acm 209 E: Ad=81(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms 210 E: Ad=02(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms 211 212 If the host side Linux system is configured properly, the ACM driver 213 should be loaded automatically. The command "lsmod" should show the 214 "acm" module is loaded. 215 216 217 Installing the Linux Host Generic USB Serial Driver 218 --------------------------------------------------- 219 To use the Linux generic USB serial driver you must configure the 220 Linux host side kernel for "Support for Host-side USB", for "USB 221 Serial Converter support", and for the "USB Generic Serial Driver". 222 223 Once the gadget serial driver is loaded and the USB device connected 224 to the Linux host with a USB cable, the host system should recognize 225 the gadget serial device. For example, the command:: 226 227 cat /sys/kernel/debug/usb/devices 228 229 should show something like this::: 230 231 T: Bus=01 Lev=01 Prnt=01 Port=01 Cnt=02 Dev#= 6 Spd=480 MxCh= 0 232 D: Ver= 2.00 Cls=ff(vend.) Sub=00 Prot=00 MxPS=64 #Cfgs= 1 233 P: Vendor=0525 ProdID=a4a6 Rev= 2.01 234 S: Manufacturer=Linux 2.6.8.1 with net2280 235 S: Product=Gadget Serial 236 S: SerialNumber=0 237 C:* #Ifs= 1 Cfg#= 1 Atr=c0 MxPwr= 2mA 238 I: If#= 0 Alt= 0 #EPs= 2 Cls=0a(data ) Sub=00 Prot=00 Driver=serial 239 E: Ad=81(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms 240 E: Ad=02(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms 241 242 You must load the usbserial driver and explicitly set its parameters 243 to configure it to recognize the gadget serial device, like this:: 244 245 echo 0x0525 0xA4A6 >/sys/bus/usb-serial/drivers/generic/new_id 246 247 The legacy way is to use module parameters:: 248 249 modprobe usbserial vendor=0x0525 product=0xA4A6 250 251 If everything is working, usbserial will print a message in the 252 system log saying something like "Gadget Serial converter now 253 attached to ttyUSB0". 254 255 256 Testing with Minicom or HyperTerminal 257 ------------------------------------- 258 Once the gadget serial driver and the host driver are both installed, 259 and a USB cable connects the gadget device to the host, you should 260 be able to communicate over USB between the gadget and host systems. 261 You can use minicom or HyperTerminal to try this out. 262 263 On the gadget side run "minicom -s" to configure a new minicom 264 session. Under "Serial port setup" set "/dev/ttygserial" as the 265 "Serial Device". Set baud rate, data bits, parity, and stop bits, 266 to 9600, 8, none, and 1--these settings mostly do not matter. 267 Under "Modem and dialing" erase all the modem and dialing strings. 268 269 On a Linux host running the ACM driver, configure minicom similarly 270 but use "/dev/ttyACM0" as the "Serial Device". (If you have other 271 ACM devices connected, change the device name appropriately.) 272 273 On a Linux host running the USB generic serial driver, configure 274 minicom similarly, but use "/dev/ttyUSB0" as the "Serial Device". 275 (If you have other USB serial devices connected, change the device 276 name appropriately.) 277 278 On a Windows host configure a new HyperTerminal session to use the 279 COM port assigned to Gadget Serial. The "Port Settings" will be 280 set automatically when HyperTerminal connects to the gadget serial 281 device, so you can leave them set to the default values--these 282 settings mostly do not matter. 283 284 With minicom configured and running on the gadget side and with 285 minicom or HyperTerminal configured and running on the host side, 286 you should be able to send data back and forth between the gadget 287 side and host side systems. Anything you type on the terminal 288 window on the gadget side should appear in the terminal window on 289 the host side and vice versa.
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