USB Serial adapter (Digitus DA-70156 USB Seriell Adapter USB 2.0)

# lsusb
Bus 006 Device 008: ID 0403:6001 Future Technology Devices International, Ltd FT232 USB-Serial (UART) IC

# create udev roule
cat << EOF | sudo tee /etc/udev/rules.d/70-usb-serial.rules
SUBSYSTEM=="tty", SUBSYSTEMS=="usb", ATTRS{idVendor}=="0403", ATTRS{idProduct}=="6001", MODE="0666"
EOF

# connect to serial port
screen /dev/ttyUSB0 115200

# buy on Amazon
http://www.amazon.de/gp/product/B0030IT780/ref=as_li_ss_tl?ie=UTF8&camp=1638&creative=19454&creativeASIN=B0030IT780&linkCode=as2&tag=wwwpanticzde-21