# Can't access /dev/ttyUSB0

## barbar

I have a card reader which connects to the usb port using an built-in usb-serial adapter. The module ch341 is loaded and usberial is loaded with modprobe usbserial vendor=0x1a86 product=0x5523.

The device works with windows. Windows also uses the ch341 driver.

dmesg shows 

```
usbcore: registered new interface driver usbserial

usbserial: USB Serial support registered for generic

usbcore: registered new interface driver usbserial_generic

usbserial: USB Serial Driver core

usbserial: USB Serial support registered for ch341-uart

usbcore: registered new interface driver ch341

usb 1-2: new full speed USB device using uhci_hcd and address 2

usb 1-2: configuration #1 chosen from 1 choice

usbserial_generic 1-2:1.0: generic converter detected

usb 1-2: generic converter now attached to ttyUSB0

```

But I can not access the device neither with cat /dev/ttyUSB0 nor with minicom /dev/ttyUSB0 (it always shows offline). I tried to intercept the communication with 

```
interceptty -l /dev/ttyUSB0
```

 But it does not capture any transmission to the device.

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## mikegpitt

Are you trying this as a normal user or as root?  If it works via root, it might mean your user is not in the plugdev group.  An alternative is that you will need to add a special udev rule to handle the device and make is user accessible.

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## barbar

I tried as root. 

I also made /dev/ttyUSB0 accessible with chmod 777 /dev/ttyUSB0

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## mikegpitt

I unfortunately don't have much experience with card readers, but did you try to mount it like a usb drive?

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## barbar

Sorry for being not exact. It is a device for reading magnetic cards. It acts more like a modem. That's why I tried t send commands with minicom. I also tried cutecom and Komport without success.

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## barbar

**bump**

I have not solved the problem yet.

Any ideas?

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## billium

I assume you know the protocol the device uses.  It works in Windows, is this with a supplied programme or hyperterminal?  Minicom status line shows off line when handshaking lines are not used.  I think it uses DCD for this flag, when using serial ports.  It may be worth trying minicom with the -o option to avoid the initialisation string.  To use minicom the user should be in uucp group.  setserial did not work for my USB serial device (prolific), though minicom works fine. cat /dev/ttyUSB0 also worked.

Billy

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## barbar

I tried 

```
minicom -o /dev/ttyUSB0
```

 as root but the problem perstists.

interceptty does not capture any data transmitted to the device.

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