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UART (Universal Asynchronous Receiver-Transmitter)

LibXR::UART provides an abstract base class for general asynchronous serial communication. It supports configuration of baud rate, data bits, stop bits, and parity, and encapsulates unified read/write interfaces for easy cross-platform adaptation.

Interface Overview​

Enum Type​

enum class Parity : uint8_t {
  NO_PARITY = 0,  // No parity
  EVEN = 1,       // Even parity
  ODD = 2         // Odd parity
};

Configuration Structure​

struct Configuration {
  uint32_t baudrate;  // Baud rate
  Parity parity;      // Parity mode
  uint8_t data_bits;  // Valid data bits; for byte-wise RX only the low data_bits bits are valid
  uint8_t stop_bits;  // Stop bit length
};

Construction and Configuration​

template <typename ReadPortType = ReadPort, typename WritePortType = WritePort>
UART(ReadPortType* read_port, WritePortType* write_port);

virtual ErrorCode SetConfig(Configuration config, bool in_isr = false) = 0;

The constructor takes read/write port pointers (derived types of ReadPort / WritePort are allowed). Internally it stores:

  • ReadPort* read_port_
  • WritePort* write_port_

When the configuration takes effect and from which contexts SetConfig() may be called depend on the backend.

Data Transmission Interfaces​

template <typename OperationType>
ErrorCode Write(ConstRawData data, OperationType&& op, bool in_isr = false);

template <typename OperationType>
ErrorCode Read(RawData data, OperationType&& op, bool in_isr = false);

Write and Read interfaces are based on the unified Port + Operation abstraction, supporting blocking, callback, and polling models. They are suitable for both main loop and asynchronous environments.

  • op must be a named WriteOperation / ReadOperation object (or a derived type); a temporary does not compile. The port copies op; the callback, polling status, or semaphore it refers to must stay valid until completion (until the call returns for BLOCK).
  • in_isr indicates whether the call happens in ISR context (forwarded to the port operator()).

Completion modes and return values are described in IO Read/Write Abstraction, Operation Model, and BLOCK Timeout and Completion Handoff; backend implementation is covered in UART Driver Design.

Notes​

  • UART::Parity supports NO_PARITY, EVEN, and ODD.
  • stop_bits is a uint8_t stop-bit count; the accepted values depend on the backend.
  • The UART base class stores read_port_ / write_port_ pointers and forwards Read() / Write(); the port objects are created and managed by the caller or the platform implementation.

Feature Summary​

  • Full configuration support for baud rate, data bits, stop bits, and parity;
  • Unified read/write interfaces supporting multiple I/O operation models;
  • Platform-independent, facilitating cross-platform adaptation and abstraction;
  • Typically implemented using underlying hardware drivers for TX/RX logic, with users not needing to handle subclass details.