protocol.h

Go to the documentation of this file.

/*
 * Copyright (c) 2025 Croxel Inc.
 * Copyright (c) 2025 CogniPilot Foundation
 *
 * SPDX-License-Identifier: Apache-2.0
 */
 
#ifndef ZEPHYR_MODEM_UBX_PROTOCOL_
#define ZEPHYR_MODEM_UBX_PROTOCOL_
 
#include <stdint.h>
#include <zephyr/modem/ubx/checksum.h>
 
#define UBX_FRAME_HEADER_SZ                     6
#define UBX_FRAME_FOOTER_SZ                     2
#define UBX_FRAME_SZ_WITHOUT_PAYLOAD            (UBX_FRAME_HEADER_SZ + UBX_FRAME_FOOTER_SZ)
#define UBX_FRAME_SZ(payload_size)              (payload_size + UBX_FRAME_SZ_WITHOUT_PAYLOAD)
 
#define UBX_PREAMBLE_SYNC_CHAR_1                0xB5
#define UBX_PREAMBLE_SYNC_CHAR_2                0x62
 
#define UBX_FRAME_PREAMBLE_SYNC_CHAR_1_IDX      0
#define UBX_FRAME_PREAMBLE_SYNC_CHAR_2_IDX      1
#define UBX_FRAME_MSG_CLASS_IDX                 2
 
#define UBX_PAYLOAD_SZ_MAX                      512
#define UBX_FRAME_SZ_MAX                        UBX_FRAME_SZ(UBX_PAYLOAD_SZ_MAX)
 
struct ubx_frame {
        uint8_t preamble_sync_char_1;
        uint8_t preamble_sync_char_2;
        uint8_t class;
        uint8_t id;
        uint16_t payload_size;
        uint8_t payload_and_checksum[];
};
 
struct ubx_frame_match {
        uint8_t class;
        uint8_t id;
        struct {
                uint8_t *buf;
                uint16_t len;
        } payload;
};
 
enum ubx_class_id {
        UBX_CLASS_ID_NAV = 0x01,  /* Navigation Results Messages */
        UBX_CLASS_ID_RXM = 0x02,  /* Receiver Manager Messages */
        UBX_CLASS_ID_INF = 0x04,  /* Information Messages */
        UBX_CLASS_ID_ACK = 0x05,  /* Ack/Nak Messages */
        UBX_CLASS_ID_CFG = 0x06,  /* Configuration Input Messages */
        UBX_CLASS_ID_UPD = 0x09,  /* Firmware Update Messages */
        UBX_CLASS_ID_MON = 0x0A,  /* Monitoring Messages */
        UBX_CLASS_ID_TIM = 0x0D,  /* Timing Messages */
        UBX_CLASS_ID_MGA = 0x13,  /* Multiple GNSS Assistance Messages */
        UBX_CLASS_ID_LOG = 0x21,  /* Logging Messages */
        UBX_CLASS_ID_SEC = 0x27,  /* Security Feature Messages */
        UBX_CLASS_ID_NMEA_STD = 0xF0, /* Note: Only used to configure message rate */
        UBX_CLASS_ID_NMEA_PUBX = 0xF1, /* Note: Only used to configure message rate */
};
 
enum ubx_msg_id_nav {
        UBX_MSG_ID_NAV_PVT = 0x07,
        UBX_MSG_ID_NAV_SAT = 0x35,
};
 
enum ubx_nav_fix_type {
        UBX_NAV_FIX_TYPE_NO_FIX = 0,
        UBX_NAV_FIX_TYPE_DR = 1,
        UBX_NAV_FIX_TYPE_2D = 2,
        UBX_NAV_FIX_TYPE_3D = 3,
        UBX_NAV_FIX_TYPE_GNSS_DR_COMBINED = 4,
        UBX_NAV_FIX_TYPE_TIME_ONLY = 5,
};
 
#define UBX_NAV_PVT_VALID_DATE                          BIT(0)
#define UBX_NAV_PVT_VALID_TIME                          BIT(1)
#define UBX_NAV_PVT_VALID_UTC_TOD                       BIT(2)
#define UBX_NAV_PVT_VALID_MAGN                          BIT(3)
 
#define UBX_NAV_PVT_FLAGS_GNSS_FIX_OK                   BIT(0)
 
#define UBX_NAV_PVT_FLAGS3_INVALID_LLH                  BIT(0)
 
struct ubx_nav_pvt {
        struct {
                uint32_t itow;
                uint16_t year;
                uint8_t month;
                uint8_t day;
                uint8_t hour;
                uint8_t minute;
                uint8_t second;
                uint8_t valid;
                uint32_t tacc;
                int32_t nano;
        } __packed time;
        uint8_t fix_type; 
        uint8_t flags;
        uint8_t flags2;
        struct {
                uint8_t num_sv;
                int32_t longitude; /* Longitude. Degrees. scaling: 1e-7 */
                int32_t latitude; /* Latitude. Degrees. scaling: 1e-7 */
                int32_t height; /* Height above ellipsoid. mm */
                int32_t hmsl; /* Height above mean sea level. mm */
                uint32_t horiz_acc; /* Horizontal accuracy estimate. mm */
                uint32_t vert_acc; /* Vertical accuracy estimate. mm */
                int32_t vel_north; /* NED north velocity. mm/s */
                int32_t vel_east; /* NED east velocity. mm/s */
                int32_t vel_down; /* NED down velocity. mm/s */
                int32_t ground_speed; /* Ground Speed (2D). mm/s */
                int32_t head_motion; /* Heading of Motion (2D). Degrees. scaling: 1e-5 */
                uint32_t speed_acc; /* Speed accuracy estimated. mm/s */
                uint32_t head_acc; 
                uint16_t pdop; /* scaling: 1e-2 */
                uint16_t flags3;
                uint32_t reserved;
                int32_t head_vehicle; /* Heading of vehicle (2D). Degrees. Valid if
                                       * flags.head_vehicle_valid is set.
                                       */
                int16_t mag_decl; /* Magnetic declination. Degrees. */
                uint16_t magacc; /* Magnetic declination accuracy. Degrees. scaling: 1e-2 */
        } __packed nav;
} __packed;
 
enum ubx_nav_sat_health {
        UBX_NAV_SAT_HEALTH_UNKNOWN = 0,
        UBX_NAV_SAT_HEALTH_HEALTHY = 1,
        UBX_NAV_SAT_HEALTH_UNHEALTHY = 2,
};
 
enum ubx_gnss_id {
        UBX_GNSS_ID_GPS = 0,
        UBX_GNSS_ID_SBAS = 1,
        UBX_GNSS_ID_GALILEO = 2,
        UBX_GNSS_ID_BEIDOU = 3,
        UBX_GNSS_ID_QZSS = 5,
        UBX_GNSS_ID_GLONASS = 6,
};
 
#define UBX_NAV_SAT_FLAGS_SV_USED                       BIT(3)
 
struct ubx_nav_sat {
        uint32_t itow;
        uint8_t version; /* Message version. */
        uint8_t num_sv;
        uint16_t reserved1;
        struct ubx_nav_sat_info {
                uint8_t gnss_id; /* See ubx_gnss_id */
                uint8_t sv_id;
                uint8_t cno; /* Carrier-to-noise ratio. dBHz */
                int8_t elevation; /* Elevation (range: +/- 90). Degrees */
                int16_t azimuth; /* Azimuth (range: 0 - 360). Degrees */
                int16_t pseu_res; /* Pseudorange Residual. Meters */
                uint32_t flags;
        } sat[];
};
 
enum ubx_msg_id_ack {
        UBX_MSG_ID_ACK = 0x01,
        UBX_MSG_ID_NAK = 0x00
};
 
enum ubx_msg_id_cfg {
        UBX_MSG_ID_CFG_PRT = 0x00,
        UBX_MSG_ID_CFG_MSG = 0x01,
        UBX_MSG_ID_CFG_RST = 0x04,
        UBX_MSG_ID_CFG_RATE = 0x08,
        UBX_MSG_ID_CFG_NAV5 = 0x24,
        UBX_MSG_ID_CFG_VAL_SET = 0x8A,
        UBX_MSG_ID_CFG_VAL_GET = 0x8B,
};
 
enum ubx_msg_id_mon {
        UBX_MSG_ID_MON_VER = 0x04,
        UBX_MSG_ID_MON_GNSS = 0x28,
};
 
struct ubx_ack {
        uint8_t class;
        uint8_t id;
};
 
#define UBX_GNSS_SELECTION_GPS                          BIT(0)
#define UBX_GNSS_SELECTION_GLONASS                      BIT(1)
#define UBX_GNSS_SELECTION_BEIDOU                       BIT(2)
#define UBX_GNSS_SELECTION_GALILEO                      BIT(3)
 
struct ubx_mon_gnss {
        uint8_t ver;
        struct {
                uint8_t supported;
                uint8_t default_enabled;
                uint8_t enabled;
        } selection;
        uint8_t simultaneous;
        uint8_t reserved1[3];
} __packed;
 
enum ubx_cfg_port_id {
        UBX_CFG_PORT_ID_DDC = 0,
        UBX_CFG_PORT_ID_UART = 1,
        UBX_CFG_PORT_ID_USB = 2,
        UBX_CFG_PORT_ID_SPI = 3,
};
 
enum ubx_cfg_char_len {
        UBX_CFG_PRT_PORT_MODE_CHAR_LEN_5 = 0, /* Not supported */
        UBX_CFG_PRT_PORT_MODE_CHAR_LEN_6 = 1, /* Not supported */
        UBX_CFG_PRT_PORT_MODE_CHAR_LEN_7 = 2, /* Supported only with parity */
        UBX_CFG_PRT_PORT_MODE_CHAR_LEN_8 = 3,
};
 
enum ubx_cfg_parity {
        UBX_CFG_PRT_PORT_MODE_PARITY_EVEN = 0,
        UBX_CFG_PRT_PORT_MODE_PARITY_ODD = 1,
        UBX_CFG_PRT_PORT_MODE_PARITY_NONE = 4,
};
 
enum ubx_cfg_stop_bits {
        UBX_CFG_PRT_PORT_MODE_STOP_BITS_1 = 0,
        UBX_CFG_PRT_PORT_MODE_STOP_BITS_1_5 = 1,
        UBX_CFG_PRT_PORT_MODE_STOP_BITS_2 = 2,
        UBX_CFG_PRT_PORT_MODE_STOP_BITS_0_5 = 3,
};
 
#define UBX_CFG_PRT_MODE_CHAR_LEN(val)                  (((val) & BIT_MASK(2)) << 6)
#define UBX_CFG_PRT_MODE_PARITY(val)                    (((val) & BIT_MASK(3)) << 9)
#define UBX_CFG_PRT_MODE_STOP_BITS(val)                 (((val) & BIT_MASK(2)) << 12)
 
#define UBX_CFG_PRT_PROTO_MASK_UBX                      BIT(0)
#define UBX_CFG_PRT_PROTO_MASK_NMEA                     BIT(1)
#define UBX_CFG_PRT_PROTO_MASK_RTCM3                    BIT(5)
 
struct ubx_cfg_prt {
        uint8_t port_id; /* See ubx_cfg_port_id */
        uint8_t reserved1;
        uint16_t rx_ready_pin;
        uint32_t mode;
        uint32_t baudrate;
        uint16_t in_proto_mask;
        uint16_t out_proto_mask;
        uint16_t flags;
        uint16_t reserved2;
};
 
enum ubx_dyn_model {
        UBX_DYN_MODEL_PORTABLE = 0,
        UBX_DYN_MODEL_STATIONARY = 2,
        UBX_DYN_MODEL_PEDESTRIAN = 3,
        UBX_DYN_MODEL_AUTOMOTIVE = 4,
        UBX_DYN_MODEL_SEA = 5,
        UBX_DYN_MODEL_AIRBORNE_1G = 6,
        UBX_DYN_MODEL_AIRBORNE_2G = 7,
        UBX_DYN_MODEL_AIRBORNE_4G = 8,
        UBX_DYN_MODEL_WRIST = 9,
        UBX_DYN_MODEL_BIKE = 10,
};
 
enum ubx_fix_mode {
        UBX_FIX_MODE_2D_ONLY = 1,
        UBX_FIX_MODE_3D_ONLY = 2,
        UBX_FIX_MODE_AUTO = 3,
};
 
enum ubx_utc_standard {
        UBX_UTC_STANDARD_AUTOMATIC = 0,
        UBX_UTC_STANDARD_GPS = 3,
        UBX_UTC_STANDARD_GALILEO = 5,
        UBX_UTC_STANDARD_GLONASS = 6,
        UBX_UTC_STANDARD_BEIDOU = 7,
};
 
#define UBX_CFG_NAV5_APPLY_DYN                  BIT(0)
#define UBX_CFG_NAV5_APPLY_FIX_MODE             BIT(2)
 
struct ubx_cfg_nav5 {
        uint16_t apply;
        uint8_t dyn_model; /* Dynamic platform model. See ubx_dyn_model */
        uint8_t fix_mode; /* Position fixing mode. See ubx_fix_mode */
        int32_t fixed_alt; /* Fixed altitude for 2D fix mode. Meters */
        uint32_t fixed_alt_var; /* Variance for Fixed altitude in 2D mode. Sq. meters */
        int8_t min_elev; /* Minimum Elevation to use a GNSS satellite in Navigation. Degrees */
        uint8_t dr_limit; /* Reserved */
        uint16_t p_dop; /* Position DOP mask */
        uint16_t t_dop; /* Time DOP mask */
        uint16_t p_acc; /* Position accuracy mask. Meters */
        uint16_t t_acc; /* Time accuracy mask. Meters */
        uint8_t static_hold_thresh; /* Static hold threshold. cm/s */
        uint8_t dgnss_timeout; /* DGNSS timeout. Seconds */
        uint8_t cno_thresh_num_svs; /* Number of satellites required above cno_thresh */
        uint8_t cno_thresh; /* C/N0 threshold for GNSS signals. dbHz */
        uint8_t reserved1[2];
        uint16_t static_hold_max_dist; /* Static hold distance threshold. Meters */
        uint8_t utc_standard; /* UTC standard to be used. See ubx_utc_standard */
        uint8_t reserved2[5];
} __packed;
 
enum ubx_cfg_rst_start_mode {
        UBX_CFG_RST_HOT_START = 0x0000,
        UBX_CFG_RST_WARM_START = 0x0001,
        UBX_CFG_RST_COLD_START = 0xFFFF,
};
 
enum ubx_cfg_rst_mode {
        UBX_CFG_RST_MODE_HW = 0x00,
        UBX_CFG_RST_MODE_SW = 0x01,
        UBX_CFG_RST_MODE_GNSS_STOP = 0x08,
        UBX_CFG_RST_MODE_GNSS_START = 0x09,
};
 
struct ubx_cfg_rst {
        uint16_t nav_bbr_mask;
        uint8_t reset_mode;
        uint8_t reserved;
};
 
enum ubx_cfg_rate_time_ref {
        UBX_CFG_RATE_TIME_REF_UTC = 0,
        UBX_CFG_RATE_TIME_REF_GPS = 1,
        UBX_CFG_RATE_TIME_REF_GLONASS = 2,
        UBX_CFG_RATE_TIME_REF_BEIDOU = 3,
        UBX_CFG_RATE_TIME_REF_GALILEO = 4,
        UBX_CFG_RATE_TIME_REF_NAVIC = 5,
};
 
struct ubx_cfg_rate {
        uint16_t meas_rate_ms;
        uint16_t nav_rate;
        uint16_t time_ref;
};
 
enum ubx_cfg_val_ver {
        UBX_CFG_VAL_VER_SIMPLE = 0,
        UBX_CFG_VAL_VER_TRANSACTION = 1,
};
 
struct ubx_cfg_val_hdr {
        uint8_t ver; /* See ubx_cfg_val_ver */
        uint8_t layer;
        uint16_t position;
} __packed;
 
struct ubx_cfg_val_u8 {
        struct ubx_cfg_val_hdr hdr;
        uint32_t key;
        uint8_t value;
} __packed;
 
struct ubx_cfg_val_u16 {
        struct ubx_cfg_val_hdr hdr;
        uint32_t key;
        uint16_t value;
} __packed;
 
struct ubx_cfg_val_u32 {
        struct ubx_cfg_val_hdr hdr;
        uint32_t key;
        uint32_t value;
} __packed;
 
enum ubx_msg_id_nmea_std {
        UBX_MSG_ID_NMEA_STD_DTM = 0x0A,
        UBX_MSG_ID_NMEA_STD_GBQ = 0x44,
        UBX_MSG_ID_NMEA_STD_GBS = 0x09,
        UBX_MSG_ID_NMEA_STD_GGA = 0x00,
        UBX_MSG_ID_NMEA_STD_GLL = 0x01,
        UBX_MSG_ID_NMEA_STD_GLQ = 0x43,
        UBX_MSG_ID_NMEA_STD_GNQ = 0x42,
        UBX_MSG_ID_NMEA_STD_GNS = 0x0D,
        UBX_MSG_ID_NMEA_STD_GPQ = 0x40,
        UBX_MSG_ID_NMEA_STD_GRS = 0x06,
        UBX_MSG_ID_NMEA_STD_GSA = 0x02,
        UBX_MSG_ID_NMEA_STD_GST = 0x07,
        UBX_MSG_ID_NMEA_STD_GSV = 0x03,
        UBX_MSG_ID_NMEA_STD_RMC = 0x04,
        UBX_MSG_ID_NMEA_STD_THS = 0x0E,
        UBX_MSG_ID_NMEA_STD_TXT = 0x41,
        UBX_MSG_ID_NMEA_STD_VLW = 0x0F,
        UBX_MSG_ID_NMEA_STD_VTG = 0x05,
        UBX_MSG_ID_NMEA_STD_ZDA = 0x08,
};
 
enum ubx_msg_id_nmea_pubx {
        UBX_MSG_ID_NMEA_PUBX_CONFIG = 0x41,
        UBX_MSG_ID_NMEA_PUBX_POSITION = 0x00,
        UBX_MSG_ID_NMEA_PUBX_RATE = 0x40,
        UBX_MSG_ID_NMEA_PUBX_SVSTATUS = 0x03,
        UBX_MSG_ID_NMEA_PUBX_TIME = 0x04,
};
 
struct ubx_cfg_msg_rate {
        uint8_t class;
        uint8_t id;
        uint8_t rate;
};
 
struct ubx_mon_ver {
        char sw_ver[30];
        char hw_ver[10];
};
 
static inline uint16_t ubx_calc_checksum(const struct ubx_frame *frame, size_t len)
{
        uint8_t ck_a = 0;
        uint8_t ck_b = 0;
        const uint8_t *data = (const uint8_t *)frame;
 
        if (len != UBX_FRAME_SZ(frame->payload_size)) {
                return 0xFFFF;
        }
 
        for (int i = UBX_FRAME_MSG_CLASS_IDX ; i < (UBX_FRAME_SZ(frame->payload_size) - 2) ; i++) {
                ck_a = ck_a + data[i];
                ck_b = ck_b + ck_a;
        }
 
        return ((ck_a & 0xFF) | ((ck_b & 0xFF) << 8));
}
 
static inline int ubx_frame_encode(uint8_t class, uint8_t id,
                                    const uint8_t *payload, size_t payload_len,
                                    uint8_t *buf, size_t buf_len)
{
        if (buf_len < UBX_FRAME_SZ(payload_len)) {
                return -EINVAL;
        }
 
        struct ubx_frame *frame = (struct ubx_frame *)buf;
 
        frame->preamble_sync_char_1 = UBX_PREAMBLE_SYNC_CHAR_1;
        frame->preamble_sync_char_2 = UBX_PREAMBLE_SYNC_CHAR_2;
        frame->class = class;
        frame->id = id;
        frame->payload_size = payload_len;
        memcpy(frame->payload_and_checksum, payload, payload_len);
 
        uint16_t checksum = ubx_calc_checksum(frame, UBX_FRAME_SZ(payload_len));
 
        frame->payload_and_checksum[payload_len] = checksum & 0xFF;
        frame->payload_and_checksum[payload_len + 1] = (checksum >> 8) & 0xFF;
 
        return UBX_FRAME_SZ(payload_len);
}
 
#define UBX_FRAME_DEFINE(_name, _frame)                                                            \
        const static struct ubx_frame _name = _frame
 
#define UBX_FRAME_ARRAY_DEFINE(_name, ...)                                                         \
        const struct ubx_frame *_name[] = {__VA_ARGS__};
 
#define UBX_FRAME_ACK_INITIALIZER(_class_id, _msg_id)                                              \
        UBX_FRAME_INITIALIZER_PAYLOAD(UBX_CLASS_ID_ACK, UBX_MSG_ID_ACK, _class_id, _msg_id)
 
#define UBX_FRAME_NAK_INITIALIZER(_class_id, _msg_id)                                              \
        UBX_FRAME_INITIALIZER_PAYLOAD(UBX_CLASS_ID_ACK, UBX_MSG_ID_NAK, _class_id, _msg_id)
 
#define UBX_FRAME_CFG_RST_INITIALIZER(_start_mode, _reset_mode)                                    \
        UBX_FRAME_INITIALIZER_PAYLOAD(UBX_CLASS_ID_CFG, UBX_MSG_ID_CFG_RST,                        \
                                      (_start_mode & 0xFF), ((_start_mode >> 8) & 0xFF),           \
                                       _reset_mode, 0)
 
#define UBX_FRAME_CFG_RATE_INITIALIZER(_meas_rate_ms, _nav_rate, _time_ref)                        \
        UBX_FRAME_INITIALIZER_PAYLOAD(UBX_CLASS_ID_CFG, UBX_MSG_ID_CFG_RATE,                       \
                                      (_meas_rate_ms & 0xFF), ((_meas_rate_ms >> 8) & 0xFF),       \
                                      (_nav_rate & 0xFF), ((_nav_rate >> 8) & 0xFF),               \
                                      (_time_ref & 0xFF), ((_time_ref >> 8) & 0xFF))
 
#define UBX_FRAME_CFG_MSG_RATE_INITIALIZER(_class_id, _msg_id, _rate)                              \
        UBX_FRAME_INITIALIZER_PAYLOAD(UBX_CLASS_ID_CFG, UBX_MSG_ID_CFG_MSG,                        \
                                      _class_id, _msg_id, _rate)
 
#define UBX_FRAME_CFG_VAL_SET_U8_INITIALIZER(_key, _value)                                         \
        UBX_FRAME_INITIALIZER_PAYLOAD(UBX_CLASS_ID_CFG, UBX_MSG_ID_CFG_VAL_SET,                    \
                                      0x00, 0x01, 0x00, 0x00,                                      \
                                      ((_key) & 0xFF), (((_key) >> 8) & 0xFF),                     \
                                      (((_key) >> 16) & 0xFF), (((_key) >> 24) & 0xFF),            \
                                      ((_value) & 0xFF))
 
#define UBX_FRAME_CFG_VAL_SET_U16_INITIALIZER(_key, _value)                                        \
        UBX_FRAME_INITIALIZER_PAYLOAD(UBX_CLASS_ID_CFG, UBX_MSG_ID_CFG_VAL_SET,                    \
                                      0x00, 0x01, 0x00, 0x00,                                      \
                                      ((_key) & 0xFF), (((_key) >> 8) & 0xFF),                     \
                                      (((_key) >> 16) & 0xFF), (((_key) >> 24) & 0xFF),            \
                                      ((_value) & 0xFF), (((_value) >> 8) & 0xFF))
 
#define UBX_FRAME_CFG_VAL_SET_U32_INITIALIZER(_key, _value)                                        \
        UBX_FRAME_INITIALIZER_PAYLOAD(UBX_CLASS_ID_CFG, UBX_MSG_ID_CFG_VAL_SET,                    \
                                      0x00, 0x01, 0x00, 0x00,                                      \
                                      ((_key) & 0xFF), (((_key) >> 8) & 0xFF),                     \
                                      (((_key) >> 16) & 0xFF), (((_key) >> 24) & 0xFF),            \
                                      ((_value) & 0xFF), (((_value) >> 8) & 0xFF),                 \
                                      (((_value) >> 16) & 0xFF), (((_value) >> 24) & 0xFF))
 
#define UBX_FRAME_CFG_VAL_GET_INITIALIZER(_key)                                                    \
        UBX_FRAME_INITIALIZER_PAYLOAD(UBX_CLASS_ID_CFG, UBX_MSG_ID_CFG_VAL_GET,                    \
                                      0x00, 0x00, 0x00, 0x00,                                      \
                                      ((_key) & 0xFF), (((_key) >> 8) & 0xFF),                     \
                                      (((_key) >> 16) & 0xFF), (((_key) >> 24) & 0xFF))
 
#define UBX_FRAME_INITIALIZER_PAYLOAD(_class_id, _msg_id, ...)                                     \
        _UBX_FRAME_INITIALIZER_PAYLOAD(_class_id, _msg_id, __VA_ARGS__)
 
#define _UBX_FRAME_INITIALIZER_PAYLOAD(_class_id, _msg_id, ...)                                    \
        {                                                                                          \
                .preamble_sync_char_1 = UBX_PREAMBLE_SYNC_CHAR_1,                                  \
                .preamble_sync_char_2 = UBX_PREAMBLE_SYNC_CHAR_2,                                  \
                .class = _class_id,                                                                \
                .id = _msg_id,                                                                     \
                .payload_size = (NUM_VA_ARGS(__VA_ARGS__)) & 0xFFFF,                               \
                .payload_and_checksum = {                                                          \
                        __VA_ARGS__,                                                               \
                        UBX_CSUM(_class_id, _msg_id,                                               \
                                 ((NUM_VA_ARGS(__VA_ARGS__)) & 0xFF),                              \
                                 (((NUM_VA_ARGS(__VA_ARGS__)) >> 8) & 0xFF),                       \
                                 __VA_ARGS__),                                                     \
                },                                                                                 \
        }
 
#define UBX_FRAME_GET_INITIALIZER(_class_id, _msg_id)                                              \
        {                                                                                          \
                .preamble_sync_char_1 = UBX_PREAMBLE_SYNC_CHAR_1,                                  \
                .preamble_sync_char_2 = UBX_PREAMBLE_SYNC_CHAR_2,                                  \
                .class = _class_id,                                                                \
                .id = _msg_id,                                                                     \
                .payload_size = 0,                                                                 \
                .payload_and_checksum = {                                                          \
                        UBX_CSUM(_class_id, _msg_id, 0, 0),                                        \
                },                                                                                 \
        }
 
#endif /* ZEPHYR_MODEM_UBX_PROTOCOL_ */