What are TTY, serial, and UART lines?
Early user terminals connected to computers through a serial line were electromechanical teleprinters or teletypewriters (TeleTYpewriter, TTY), and since then, TTY has continued to be used as the name for such text-only console and the relative serial port. In fact, in a GNU/Linux system, a serial port is usually referred to in the /dev
directory with the /dev/ttyS0
, /dev/ttyS1
, /dev/ttyUSB0
, or /dev/ttyUSB1
device for the USB emulated devices, as we already saw in the previous chapters.
So a serial port is not a peripheral, but it is just a serial communication interface through which information transfers in or out one bit at a time. This communication is implemented by modern computers via a Universal Asynchronous Receiver/Transmitter (UART) device, which has a side connected to the main CPU and the other side with a circuitry, that is, a physical interface (Phy in the following diagram) useful to translate the electronic signals in a suitable form...