userdoc:usbtty_serial_login [AstLinux Documentation]

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====== USB TTY Serial Login ======

Many **Generic x86 Boards and Appliances** provide a DB9-RS232 serial port for console access, and since modern PC's / Notebooks / Chromebooks do not have a serial port, a USB-to-Serial cable adapter must be used.  You probably already knew that.

What is new is the ability to connect a second USB-to-Serial cable adapter (USB-to-Serial <-> Serial-to-USB) to a USB port on your AstLinux box and automatically spawn getty to establish a login.  This is particularly useful for **Generic x86 Boards and Appliances** that only have a VGA video console, or to establish one or more serial logins in addition to a serial console.  The USB TTY serial baudrate and terminal type can be specified independently from the system console configuration.

!!Note: AstLinux 1.2.10 or later is required!!

**Configuration:**

Enable this feature by setting ''USBTTY'' to ''yes'':

''/mnt/kd/rc.conf.d/user.conf''

  USBTTY="yes"

The default baud rate is ''115200'', you may specify a different baud rate //(for example)//:

  USBTTY_BAUD_RATE="19200"

The default terminal type is ''vt100'', you may specify a different terminal type //(for example)//:

  USBTTY_TERM_TYPE="xterm-color"

**Equipment:**

It is recommended to use a USB-to-Serial adapter containing a FTDI chipset, which is supported in AstLinux and is built-in to most modern OS's including Chromebooks.  The older PL2303 Prolific Chipset adapter will also work if you already have one.

The two USB-to-Serial adapters are connected together with a DB9 [[wp>Null_modem|Null Modem]] cable or mini adapter.  A crossover connection, **not** straight through.

To be clear, the back-to-back USB-to-Serial adapters do not have to use the same chipset or brand, as long as internal driver support exists for each USB end, respectively.

**Operation:**

Join the two USB-to-Serial adapters together using a DB9 Null Modem cable or adapter.

Plug one USB connector into your PC / Notebook / Chromebook, start a terminal emulator (screen, minicom, etc.) at 115200 baud (unless changed).

!!Tip ->!! ''screen /dev/ttyUSB0 115200''

!!Tip ->!! ''minicom -D /dev/ttyUSB0 -b 115200''

Plug the other USB connector into your AstLinux box.
You should immediately see a login prompt on your terminal emulator screen.

**Photos:**

{{:userdoc:usbtty-serial-login.jpg?nolink|USB Cable Set}}

USB 2.0 to RS232 DB9 Serial Cable Male A Converter Adapter with FTDI Chipset\\
https://www.amazon.com/dp/B00QUZY4L0/

DB9 Female / DB9 Female Null Modem Mini Adapter\\
https://www.amazon.com/dp/7507825604/