Library Architecture¶

EasyNMEA is divided into three levels (from outer to inner):

API Level : This level contains all public API, i.e. the classes in the include directory.
Implementation Level: This level contains all the internal classes which provide functionality to the library.
Serial Interface Level: This level contains the classes for interacting with the serial port (through Asio).

@startuml
skinparam linetype ortho

component [API Level] as api_level
component [Implementation Level] as impl_level
component [Serial Interface Level] as serial_level

api_level <.. impl_level
impl_level <.. serial_level

@enduml

API Level¶

The API level comprises all the EasyNMEA public classes and structures, and acts as entry point for the library’s functionalities. It consists of a main class EasyNmea, which provides application with access to the functionalities, and all the supporting classes and structures for return types and input and output parameters. Those companion classes and structures are ReturnCode, GPGGAData, and NMEA0183DataKindMask. For the actual functionality implementation, EasyNmea relies on the internal class EasyNmeaImpl.

Implementation Level¶

The implementation level comprises two main components:

The EasyNmeaImpl class, which provides with implementation for the EasyNmea public API, i.e opening and closing the serial port, waiting until data of one or more NMEA 0183 types has been received, checking whether the serial port connection is opened, and taking the next unread sample of a given NMEA 0183 type. The EasyNmeaImpl holds a FixedSizeQueue of ten elements for each supported NMEA 0183 type. This way, keeping outdated samples, as well as dynamic allocation of data samples, is avoided. The managing of the serial port is enabled through the SerialInterface class.
The EasyNmeaCoder class, which provides APIs for decode NMEA 0183 sentences (and to encode them in the future).

$@startuml hide empty members EasyNmeaImpl : EasyNmeaImpl() noexcept EasyNmeaImpl : virtual ReturnCode open(const char* serial_port, long baudrate) noexcept EasyNmeaImpl : virtual bool is_open() noexcept EasyNmeaImpl : virtual ReturnCode close() noexcept EasyNmeaImpl : virtual ReturnCode take_next(GPGGAData& gpgga) noexcept EasyNmeaImpl : virtual ReturnCode wait_for_data(NMEA0183DataKindMask data_mask, std::chrono::milliseconds timeout) noexcept class FixedSizeQueue<typename T, int max_size, typename Container = std::deque<T>> class SerialInterface<asio::serial_port> class EasyNmeaCoder { + static std::shared_ptr<NMEA0183Data> decode(const std::string& sentence) noexcept --- # static std::shared_ptr<GPGGAData> decode_gpgga_(const std::string gpgga_sentence) noexcept # static NMEA0183DataKind data_kind_(const std::string& sentence) noexcept # static bool validate_checksum_(const std::string& sentence) noexcept # static std::vector<std::string> split_(const std::string& sentence, char separator) noexcept # static float to_degrees_(const std::string& nmea_angle) noexcept } class NMEA0183Data { NMEA0183DataKind kind } class GPGGAData { float timestamp float latitude float longitude uint16_t fix uint16_t satellites_on_view float horizontal_precision float altitude float height_of_geoid float dgps_last_update uint16_t dgps_reference_station_id } class NMEA0183DataKind { INVALID GPGGA } NMEA0183Data <|-- GPGGAData NMEA0183Data <.. NMEA0183DataKind : <<uses>> EasyNmeaCoder <.. NMEA0183Data : <<uses>> EasyNmeaCoder <.. GPGGAData : <<uses>> EasyNmeaImpl o-- "n" FixedSizeQueue EasyNmeaImpl o-- "1" SerialInterface EasyNmeaImpl <.. EasyNmeaCoder : <<uses>> @enduml$

Serial Interface Level¶

The serial interface level is comprised of the SerialInterface class, which provides member functions to open and close a serial port, as well as for reading data from it. SerialInterface is a template class with a template parameter SerialPort that defines the serial port implementation, which defaults to :class: asio::serial_port.