mtk.h

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/**
 * @file mtk.h
 *
 * @author Thomas Gubler <thomasgubler@student.ethz.ch>
 * @author Julian Oes <julian@oes.ch>
 */

#pragma once

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

#define MTK_SYNC1_V16 0xd0
#define MTK_SYNC1_V19 0xd1
#define MTK_SYNC2 0xdd

#define MTK_OUTPUT_5HZ      "$PMTK220,200*2C\r\n"
#define MTK_SET_BINARY      "$PGCMD,16,0,0,0,0,0*6A\r\n"
#define MTK_SBAS_ON         "$PMTK313,1*2E\r\n"
#define MTK_WAAS_ON     "$PMTK301,2*2E\r\n"
#define MTK_NAVTHRES_OFF    "$PMTK397,0*23\r\n"

#define MTK_TIMEOUT_5HZ 400
#define MTK_BAUDRATE 38400

typedef enum {
    MTK_DECODE_UNINIT = 0,
    MTK_DECODE_GOT_CK_A = 1,
    MTK_DECODE_GOT_CK_B = 2
} mtk_decode_state_t;

/** the structures of the binary packets */
#pragma pack(push, 1)

typedef struct {
    uint8_t payload; ///< Number of payload bytes
    int32_t latitude;  ///< Latitude in degrees * 10^7
    int32_t longitude; ///< Longitude in degrees * 10^7
    uint32_t msl_altitude;  ///< MSL altitude in meters * 10^2
    uint32_t ground_speed; ///< velocity in m/s
    int32_t heading; ///< heading in degrees * 10^2
    uint8_t satellites; ///< number of satellites used
    uint8_t fix_type;  ///< fix type: XXX correct for that
    uint32_t date;
    uint32_t utc_time;
    uint16_t hdop; ///< horizontal dilution of position (without unit)
    uint8_t ck_a;
    uint8_t ck_b;
} gps_mtk_packet_t;

#pragma pack(pop)

#define MTK_RECV_BUFFER_SIZE 40

class GPSDriverMTK : public GPSHelper
{
public:
    GPSDriverMTK(GPSCallbackPtr callback, void *callback_user, struct vehicle_gps_position_s *gps_position);
    virtual ~GPSDriverMTK() = default;

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

private:
    /**
     * Parse the binary MTK packet
     */
    int parseChar(uint8_t b, gps_mtk_packet_t &packet);

    /**
     * Handle the package once it has arrived
     */
    void handleMessage(gps_mtk_packet_t &packet);

    /**
     * Reset the parse state machine for a fresh start
     */
    void decodeInit();

    /**
     * While parsing add every byte (except the sync bytes) to the checksum
     */
    void addByteToChecksum(uint8_t);

    struct vehicle_gps_position_s *_gps_position {nullptr};
    mtk_decode_state_t _decode_state{MTK_DECODE_UNINIT};
    uint8_t _mtk_revision{0};
    unsigned _rx_count{};
    uint8_t _rx_ck_a{};
    uint8_t _rx_ck_b{};
};