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I have a device that is correctly connected to my PC . But i could not see it in /dev. what does it mean? Is it because of not installing my device?

$ /dev ls before connecting my device:

agpgart          mei                 sda1      tty28  tty59      ttyS30
autofs           mem                 sda2      tty29  tty6       ttyS31
block            net                 sda5      tty3   tty60      ttyS4
bsg              network_latency     sda6      tty30  tty61      ttyS5
btrfs-control    network_throughput  serial    tty31  tty62      ttyS6
bus              null                sg0       tty32  tty63      ttyS7
char             oldmem              shm       tty33  tty7       ttyS8
console          parport0            snapshot  tty34  tty8       ttyS9
core             port                snd       tty35  tty9       ttyUSB0
cpu              ppp                 stderr    tty36  ttyprintk  uinput
cpu_dma_latency  psaux               stdin     tty37  ttyS0      urandom
disk             ptmx                stdout    tty38  ttyS1      usbmon0
dri              pts                 tty       tty39  ttyS10     usbmon1
ecryptfs         ram0                tty0      tty4   ttyS11     usbmon2
fb0              ram1                tty1      tty40  ttyS12     vcs
fd               ram10               tty10     tty41  ttyS13     vcs1
full             ram11               tty11     tty42  ttyS14     vcs2
fuse             ram12               tty12     tty43  ttyS15     vcs3
hidraw0          ram13               tty13     tty44  ttyS16     vcs4
hpet             ram14               tty14     tty45  ttyS17     vcs5
input            ram15               tty15     tty46  ttyS18     vcs6
kmsg             ram2                tty16     tty47  ttyS19     vcsa
log              ram3                tty17     tty48  ttyS2      vcsa1
loop0            ram4                tty18     tty49  ttyS20     vcsa2
loop1            ram5                tty19     tty5   ttyS21     vcsa3
loop2            ram6                tty2      tty50  ttyS22     vcsa4
loop3            ram7                tty20     tty51  ttyS23     vcsa5
loop4            ram8                tty21     tty52  ttyS24     vcsa6
loop5            ram9                tty22     tty53  ttyS25     vga_arbiter
loop6            random              tty23     tty54  ttyS26     zero
loop7            rfkill              tty24     tty55  ttyS27
lp0              rtc                 tty25     tty56  ttyS28
mapper           rtc0                tty26     tty57  ttyS29
mcelog           sda                 tty27     tty58  ttyS3

$ /dev ls after connecting my device:

agpgart          mei                 sda1      tty28  tty59      ttyS30
autofs           mem                 sda2      tty29  tty6       ttyS31
block            net                 sda5      tty3   tty60      ttyS4
bsg              network_latency     sda6      tty30  tty61      ttyS5
btrfs-control    network_throughput  serial    tty31  tty62      ttyS6
bus              null                sg0       tty32  tty63      ttyS7
char             oldmem              shm       tty33  tty7       ttyS8
console          parport0            snapshot  tty34  tty8       ttyS9
core             port                snd       tty35  tty9       ttyUSB0
cpu              ppp                 stderr    tty36  ttyprintk  ttyUSB1
cpu_dma_latency  psaux               stdin     tty37  ttyS0      uinput
disk             ptmx                stdout    tty38  ttyS1      urandom
dri              pts                 tty       tty39  ttyS10     usbmon0
ecryptfs         ram0                tty0      tty4   ttyS11     usbmon1
fb0              ram1                tty1      tty40  ttyS12     usbmon2
fd               ram10               tty10     tty41  ttyS13     vcs
full             ram11               tty11     tty42  ttyS14     vcs1
fuse             ram12               tty12     tty43  ttyS15     vcs2
hidraw0          ram13               tty13     tty44  ttyS16     vcs3
hpet             ram14               tty14     tty45  ttyS17     vcs4
input            ram15               tty15     tty46  ttyS18     vcs5
kmsg             ram2                tty16     tty47  ttyS19     vcs6
log              ram3                tty17     tty48  ttyS2      vcsa
loop0            ram4                tty18     tty49  ttyS20     vcsa1
loop1            ram5                tty19     tty5   ttyS21     vcsa2
loop2            ram6                tty2      tty50  ttyS22     vcsa3
loop3            ram7                tty20     tty51  ttyS23     vcsa4
loop4            ram8                tty21     tty52  ttyS24     vcsa5
loop5            ram9                tty22     tty53  ttyS25     vcsa6
loop6            random              tty23     tty54  ttyS26     vga_arbiter
loop7            rfkill              tty24     tty55  ttyS27     zero
lp0              rtc                 tty25     tty56  ttyS28
mapper           rtc0                tty26     tty57  ttyS29
mcelog           sda                 tty27     tty58  ttyS3

$ lsusb :

Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 002: ID 8087:0020 Intel Corp. Integrated Rate Matching Hub
Bus 002 Device 002: ID 8087:0020 Intel Corp. Integrated Rate Matching Hub
Bus 002 Device 003: ID 093a:2510 Pixart Imaging, Inc. Optical Mouse
Bus 002 Device 004: ID 1a40:0101 TERMINUS TECHNOLOGY INC. USB-2.0 4-Port HUB
Bus 002 Device 005: ID 067b:2303 Prolific Technology, Inc. PL2303 Serial Port
Bus 002 Device 008: ID 067b:2303 Prolific Technology, Inc. PL2303 Serial Port

ttyUSBX is just a usb hardware that linux detected as an attached device but it is not communicable as a serial port. in windows we have COMX port and USB device and while Serial driver not installed it can not be used as COM Port. i think ttyUSBX should first detected as a COM Port (ttysX)!

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2 Answers

up vote 0 down vote accepted
  1. Unplug your device
  2. Type tail -F /var/log/kern.log
  3. Replug your device
  4. There will be a line stating something like:

    [1060037.921203] usb 2-2.1: Prolific Technology, Inc. PL2303 Serial Port converter now attached to ttyUSB1

In this case the device is attached to /dev/ttyUSB1

Using udev, it might be possible to create a symlink with a name that doesn't change with replugging. Now the Serial Port converters get a ttyUSB name in order they are plugged. It is outside the scope of this question, so create a specific one when required.

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ttyUSBX is just a usb hardware that linux detected as an attached device but it is not communicable as a serial port. in windows we have COMX port and USB device and while Serial driver not installed it can not be used as COM Port. i think ttyUSBX should first detected as a COM Port (ttysX)! –  mefmef Apr 14 '12 at 9:00
    
ttyUSBx works just fine for me. –  jippie Apr 14 '12 at 9:16
    
you mean you send and receive characters via ttyUSBx ????? could you please tell me your port configuration? –  mefmef Apr 14 '12 at 9:28
    
My port configuration will probably not work for you. I like cutecom for its simple interface, but most of my projects are just addressing the port through Perl programming language. Most ttyUSB devices default to 9600 8N1 => 9600Bd, 8 databits, No parity, 1 stopbit. –  jippie Apr 14 '12 at 9:33
    
I install cutecom but it does not working for me. –  mefmef Apr 14 '12 at 9:41
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While it might not be immediately obvious, there is an extra /dev/ttyUSB1 entry in the second listing of /dev. That would be the second USB serial device you plugged in (I assume you left the first one connected, which shows up as `/dev/ttyUSB0 in both listings).

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your right but i want to communicate with my serial port and it should be a serial port (ttyS#) not just a USB device. –  mefmef Apr 14 '12 at 7:31
    
The ttyUSBX device node does let you use the port as a serial device. The ttySX nodes are bound to driver for legacy UART style serial ports. –  James Henstridge Apr 14 '12 at 7:33
    
Renaming a device node requires udev. Why do you require it to be ttySx? –  jippie Apr 14 '12 at 7:52
    
because i want to use some serial comm program like mincom or moserial terminal –  mefmef Apr 14 '12 at 7:57
    
You should be able to use the ttyUSBX device with those programs. –  James Henstridge Apr 14 '12 at 8:08
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