Documentation/usb/gadget_serial.rst

7 (updated 8-May-2008 for v2.3)
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25 MA 02111-1307 USA.
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44 USB and serial devices.  It also assumes you configure the Linux
45 gadget and usb drivers as modules.
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
59 with a USB development card.
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::
64    Host
65    --------------------------------------
66   | Host-Side   CDC ACM       USB Host   |
67   | Operating |   or        | Controller |   USB
68   | System    | Generic USB | Driver     |--------
70   | Windows)    Driver        USB Stack  |        |
71    --------------------------------------         |
76    --------------------------------------         |
77   | Gadget                   USB Periph. |        |
78   | Device-Side |  Gadget  | Controller  |        |
79   | Linux       |  Serial  | Driver      |--------
81   | System                   USB Stack   |
82    --------------------------------------
84 On the device-side Linux system, the gadget serial driver looks
87 On the host-side system, the gadget serial device looks like a
92 The host side driver can potentially be any ACM compliant driver
95 the Windows usbser.sys ACM driver, and the Linux USB generic serial
98 With the gadget serial driver and the host side ACM or generic
100 the host and the gadget side systems as if they were connected by a
109 -----------------------------------
111 side kernel for "Support for USB Gadgets", for a "USB Peripheral
113 driver.  All this are listed under "USB Gadget Support" when
135   # ls -l /dev/ttyGS0 | cat
136   crw-rw----    1 root     root     253,   0 May  8 14:10 /dev/ttyGS0
139 Note that the major number (253, above) is system-specific.  If
149 either the Windows or Linux ACM driver on the host side.  If gadget
151 Linux generic serial driver on the host side.  Follow the appropriate
152 instructions below to install the host side driver.
155 Installing the Windows Host ACM Driver
156 --------------------------------------
157 To use the Windows ACM driver you must have the "linux-cdc-acm.inf"
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
164 driver in the folder that contains the "linux-cdc-acm.inf" file.
170 path or browse to the folder containing the "linux-cdc-acm.inf" file.
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)
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
195   cat /sys/kernel/debug/usb/devices
212 If the host side Linux system is configured properly, the ACM driver
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".
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
227   cat /sys/kernel/debug/usb/devices
245   echo 0x0525 0xA4A6 >/sys/bus/usb-serial/drivers/generic/new_id
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.
263 On the gadget side run "minicom -s" to configure a new minicom
266 to 9600, 8, none, and 1--these settings mostly do not matter.
269 On a Linux host running the ACM driver, configure minicom similarly
273 On a Linux host running the USB generic serial driver, configure
275 (If you have other USB serial devices connected, change the device
278 On a Windows host configure a new HyperTerminal session to use the
281 device, so you can leave them set to the default values--these
285 minicom or HyperTerminal configured and running on the host side,
287 side and host side systems.  Anything you type on the terminal
289 the host side and vice versa.