examples/read_nmea_boostasio.cpp

   1 /// This example shows how to use Boost.ASIO in order to read synchronously
   2 /// NMEA data from a serial port.
   3
   4 #include <iostream>
   5 #include <boost/asio.hpp>
   6 #include <marnav/io/default_nmea_reader.hpp>
   7 #include <marnav/nmea/nmea.hpp>
   8 #include <marnav/nmea/rmc.hpp>
   9 #include <marnav/nmea/io.hpp>
  10
  11 namespace marnav_example
  12 {
  13
  14 /// Synchronous reading of the serial port using Boost.ASIO
  15 class boost_asio_serial : public marnav::io::device
  16 {
  17 public:
  18         boost_asio_serial(const std::string & port)
  19                 : io()
  20                 , serial(io, port)
  21         {
  22                 serial.set_option(boost::asio::serial_port_base::baud_rate(4800));
  23         }
  24
  25         virtual void open() override {}
  26
  27         virtual void close() override { serial.close(); }
  28
  29         virtual int read(char * buffer, uint32_t size) override
  30         {
  31                 if ((buffer == nullptr) || (size == 0))
  32                         throw std::invalid_argument{"invalid buffer or size"};
  33                 if (!serial.is_open())
  34                         throw std::runtime_error{"device not open"};
  35
  36                 return boost::asio::read(serial, boost::asio::buffer(buffer, size));
  37         }
  38
  39         virtual int write(const char *, uint32_t) override
  40         {
  41                 throw std::runtime_error{"operation not supported"};
  42         }
  43
  44 private:
  45         boost::asio::io_service io;
  46         boost::asio::serial_port serial;
  47 };
  48
  49 /// This subclassing is not really necessary, but hides the instantiation
  50 /// of boost_asio_serial from normal usage (see function 'main'). This way
  51 /// it is completley transparent whether or not Boost.ASIO is in use or not
  52 /// from the perspective of just using it.
  53 class sentence_reader : public marnav::io::default_nmea_reader
  54 {
  55 public:
  56         sentence_reader(const std::string & port)
  57                 : default_nmea_reader(std::unique_ptr<marnav::io::device>{new boost_asio_serial{port}})
  58         {
  59         }
  60 };
  61 }
  62
  63 int main(int, char **)
  64 {
  65         using namespace marnav;
  66
  67         // create and open the device for reading.
  68         marnav_example::sentence_reader reader{"/dev/ttyUSB0"};
  69
  70         std::string data;
  71
  72         // read and process NMEA sentences, bus synchronization is done automatically.
  73         while (reader.read_sentence(data)) {
  74                 // data was successfully read from the NMEA bus, inclusive synchronization
  75                 // of NMEA sentences. This means it is possible to begin to listen on the
  76                 // bus at any time.
  77                 auto sentence = nmea::make_sentence(data);
  78
  79                 // do something with the sentence, for example dump the position
  80                 if (sentence->id() == nmea::sentence_id::RMC) {
  81                         auto rmc = nmea::sentence_cast<nmea::rmc>(sentence);
  82                         std::cout << "latitude : " << nmea::to_string(rmc->get_latitude()) << "\n";
  83                         std::cout << "longitude: " << nmea::to_string(rmc->get_longitude()) << "\n";
  84                 }
  85         }
  86 }