emlid_reach.h

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/**
 * @file emlid_reach.h
 *
 * @author Bastien Auneau <bastien.auneau@while-true.fr>
 */

#pragma once

#include "gps_helper.h"
#include "../../definitions.h"

// Emlid documentation
//   https://docs.emlid.com/reachm-plus/
//   https://files.emlid.com/ERB.pdf

#define ERB_HEADER_LEN           5
// Not using ERB_ID_SPACE_INFO, so use a smaller buff length
#define ERB_SENTENCE_MAX_LEN     (sizeof(erb_message_t))

#define MAX_CONST(a, b) ((a>b) ? a : b)

// Emlid ERB message definition
#pragma pack(push, 1)

typedef struct {
    uint8_t     sync1;
    uint8_t     sync2;
    uint8_t     id;
    uint16_t    length;
} erb_header_t;

typedef struct {
    uint8_t         ck_a;
    uint8_t         ck_b;
} erb_checksum_t;

typedef struct {
    uint32_t        timeGPS;
    uint8_t         verH;
    uint8_t         verM;
    uint8_t         verL;
    erb_checksum_t  checksum;
} erb_version_t;

typedef struct {
    uint32_t        timeGPS;
    double          longitude;
    double          latitude;
    double          altElipsoid;
    double          altMeanSeaLevel;
    uint32_t        accHorizontal;
    uint32_t        accVertical;
    erb_checksum_t  checksum;
} erb_geodic_position_t;

typedef struct {
    uint32_t        timeGPS;
    uint16_t        weekGPS;
    uint8_t         fixType;
    uint8_t         fixStatus;
    uint8_t         numSatUsed;
    erb_checksum_t  checksum;
} erb_navigation_status_t;

typedef struct {
    uint32_t        timeGPS;
    uint16_t        dopGeometric;
    uint16_t        dopPosition;
    uint16_t        dopVertical;
    uint16_t        dopHorizontal;
    erb_checksum_t  checksum;
} erb_dop_t;

typedef struct {
    uint32_t        timeGPS;
    int32_t         velN;
    int32_t         velE;
    int32_t         velD;
    uint32_t        speed;
    int32_t         heading;
    uint32_t        speedAccuracy;
    erb_checksum_t  checksum;
} erb_ned_velocity_t;

typedef union {
    erb_version_t           version;
    erb_geodic_position_t   geodic_position;
    erb_navigation_status_t navigation_status;
    erb_dop_t               dop;
    erb_ned_velocity_t      ned_velocity;
} erb_payload_t;

typedef struct {
    erb_header_t    header;
    erb_payload_t   payload;
} erb_message_t;

#pragma pack(pop)


/**
 * Driver class for Emlid Reach
 * Populates caller provided vehicle_gps_position_s
 * Some ERB messages are cached and correlated by timestamp before publishing it
 */
class GPSDriverEmlidReach : public GPSHelper
{
public:
    GPSDriverEmlidReach(GPSCallbackPtr callback, void *callback_user,
                struct vehicle_gps_position_s *gps_position,
                struct satellite_info_s *satellite_info
               );

    virtual ~GPSDriverEmlidReach() = default;

    int receive(unsigned timeout) override;
    int configure(unsigned &baudrate, OutputMode output_mode) override;

private:

    enum class ERB_State {
        init = 0,
        got_sync_1,  // E
        got_sync_2,  // R
        got_id,
        got_len_1,
        got_len_2,
        got_payload,
        got_CK_A
    };


    /** NMEA parser state machine */
    ERB_State _erb_decode_state;

    /** Buffer used by parser to build ERB sentences */
    erb_message_t _erb_buff{};
    uint16_t _erb_buff_cnt{};

    /** Buffer used by parser to build ERB checksum */
    erb_checksum_t _erb_checksum{};
    uint8_t _erb_checksum_cnt{};

    /** Pointer provided by caller, ie gps.cpp */
    struct vehicle_gps_position_s *_gps_position {nullptr};
    /** Pointer provided by caller, gps.cpp */
    struct satellite_info_s *_satellite_info {nullptr};

    bool _testing_connection{false};
    /** counts decoded sentence when testing connection */
    unsigned _sentence_cnt{0};

    uint16_t _erb_payload_len{0};

    uint32_t _last_POS_timeGPS{0};
    uint32_t _last_VEL_timeGPS{0};
    bool _POS_received{false};
    bool _VEL_received{false};


    ///// ERB messages caches /////
    uint8_t _fix_type{0};
    uint8_t _fix_status{0};
    uint8_t _satellites_used{0};
    float _hdop{0};
    float _vdop{0};


    /** Feed ERB parser with received bytes from serial
     * @return len of decoded message, 0 if not completed, -1 if error
     */
    int erbParseChar(uint8_t b);

    /** ERB sentence into vehicle_gps_position_s or satellite_info_s, to be used by GPSHelper
     *  @return 1 if gps_position updated, 2 for satellite_info_s (can be bit OR), 0 for nothing
     */
    int handleErbSentence();

    void computeNedVelocity();

    bool testConnection();

};