===================== Serial Device Drivers

• include/nuttx/serial/serial.h. All structures and APIs needed to work with serial drivers are provided in this header file.

• struct uart_ops_s. Each serial device driver must implement an instance of struct uart_ops_s. That structure defines a call table with the following methods:

• int uart_register(FAR const char *path, FAR uart_dev_t *dev);. A serial driver may register itself by calling uart_register(), passing it the path where it will appear in the :ref:pseudo file system <file_system_overview> and it's initialized instance of struct uart_ops_s. By convention, serial device drivers are registered at paths like /dev/ttyS0, /dev/ttyS1, etc. See the uart_register() implementation in drivers/serial.c.

• TTY_LAUNCH this depends on CONFIG_TTY_LAUNCH, this feature allow user launch a new program with a special char input.

  e.g. use ctrl+R to start a nuttx shell. e.g. use ctrl+E to start user entry.

  You can use TTY_LAUNCH_CHAR to customize which special char.

  You can choose launch method: TTY_LAUNCH_ENTRY or TTY_LAUNCH_FILE, IfTTY_LAUNCH_ENTRY you can set program entry by TTY_LAUNCH_ENTRYPOINT. IfTTY_LAUNCH_FILE you can set file path by TTY_LAUNCH_FILEPATH.

  Also, you can customize: TTY_LAUNCH_ARGS TTY_LAUNCH_PRIORITY TTY_LAUNCH_STACKSIZE

• User Access. Serial drivers are, ultimately, normal character drivers and are accessed as other character drivers.

• Examples: arch/arm/src/stm32/stm32_serial.c, arch/arm/src/lpc214x/lpc214x_serial.c, arch/z16/src/z16f/z16f_serial.c, etc.