ardupilot/libraries/AP_GPS/GPS.h

177 lines
4.3 KiB
C++

// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: t -*-
/// @file GPS.h
/// @brief Interface definition for the various GPS drivers.
#ifndef GPS_h
#define GPS_h
#include <inttypes.h>
#include <Stream.h>
/// @class GPS
/// @brief Abstract base class for GPS receiver drivers.
class GPS
{
public:
/// Update GPS state based on possible bytes received from the module.
///
/// This routine must be called periodically to process incoming data.
///
/// GPS drivers should not override this function; they should implement
/// ::read instead.
///
void update(void);
/// GPS status codes
///
/// \note Non-intuitive ordering for legacy reasons
///
enum GPS_Status {
NO_GPS = 0, ///< No GPS connected/detected
NO_FIX = 1, ///< Receiving valid GPS messages but no lock
GPS_OK = 2 ///< Receiving valid messages and locked
};
/// Query GPS status
///
/// The 'valid message' status indicates that a recognised message was
/// received from the GPS within the last 500ms.
///
/// @returns Current GPS status
///
GPS_Status status(void) { return _status; }
/// Startup initialisation.
///
/// This routine performs any one-off initialisation required to set the
/// GPS up for use.
///
/// Must be implemented by the GPS driver.
///
virtual void init(void) = 0;
// Properties
long time; ///< GPS time (FORMAT TBD)
long date; ///< GPS date (FORMAT TBD)
long latitude; ///< latitude in degrees * 10,000,000
long longitude; ///< longitude in degrees * 10,000,000
long altitude; ///< altitude in cm
long ground_speed; ///< ground speed in cm/sec
long ground_course; ///< ground course in 100ths of a degree
long speed_3d; ///< 3D speed in cm/sec (not always available)
int hdop; ///< horizontal dilution of precision in cm
uint8_t num_sats; ///< Number of visible satelites
/// Set to true when new data arrives. A client may set this
/// to false in order to avoid processing data they have
/// already seen.
bool new_data;
// Deprecated properties
bool fix; ///< true if we have a position fix (use ::status instead)
bool valid_read; ///< true if we have seen data from the GPS (use ::status instead)
// Debug support
bool print_errors; ///< deprecated
protected:
Stream *_port; ///< port the GPS is attached to
/// Constructor
///
/// @note The stream is expected to be set up and configured for the
/// correct bitrate before ::init is called.
///
/// @param s Stream connected to the GPS module.
///
GPS(Stream *s) : _port(s) {};
/// read from the GPS stream and update properties
///
/// Must be implemented by the GPS driver.
///
/// @returns true if a valid message was received from the GPS
///
virtual bool read(void) = 0;
/// perform an endian swap on a long
///
/// @param bytes pointer to a buffer containing bytes representing a
/// long in the wrong byte order
/// @returns endian-swapped value
///
long _swapl(const void *bytes);
/// perform an endian swap on an int
///
/// @param bytes pointer to a buffer containing bytes representing an
/// int in the wrong byte order
/// @returns endian-swapped value
int _swapi(const void *bytes);
/// emit an error message
///
/// based on the value of print_errors, emits the printf-formatted message
/// in msg,... to stderr
///
/// @param fmt printf-like format string
///
/// @note deprecated as-is due to the difficulty of hooking up to a working
/// printf vs. the potential benefits
///
void _error(const char *msg);
private:
/// Time in milliseconds after which we will assume the GPS is no longer
/// sending us updates and attempt a re-init.
///
/// 1200ms allows a small amount of slack over the worst-case 1Hz update
/// rate.
///
static const unsigned long _idleTimeout = 1200;
/// Last time that the GPS driver got a good packet from the GPS
///
unsigned long _idleTimer;
/// Our current status
GPS_Status _status;
};
inline long
GPS::_swapl(const void *bytes)
{
const uint8_t *b = (const uint8_t *)bytes;
union {
long v;
uint8_t b[4];
} u;
u.b[0] = b[3];
u.b[1] = b[2];
u.b[2] = b[1];
u.b[3] = b[0];
return(u.v);
}
inline int16_t
GPS::_swapi(const void *bytes)
{
const uint8_t *b = (const uint8_t *)bytes;
union {
int16_t v;
uint8_t b[2];
} u;
u.b[0] = b[1];
u.b[1] = b[0];
return(u.v);
}
#endif