epan/dissectors/packet-ubx-gps_l1_lnav.c

   1 /* packet-ubx-gps_l1_lnav.c
   2  * Dissection of Global Positioning System (GPS) L1 C/A LNAV navigation messages
   3  * (as provided by UBX-RXM-SFRBX).
   4  *
   5  * By Timo Warns <timo.warns@gmail.com>
   6  * Copyright 2023 Timo Warns
   7  *
   8  * Wireshark - Network traffic analyzer
   9  * By Gerald Combs <gerald@unicom.net>
  10  * Copyright 1998 Gerald Combs
  11  *
  12  * SPDX-License-Identifier: GPL-2.0-or-later
  13  */
  14
  15 #include "config.h"
  16
  17 #include <epan/expert.h>
  18 #include <epan/packet.h>
  19
  20 #include "packet-ubx.h"
  21
  22 /*
  23  * Dissects GPS L1 C/A LNAV navigation messages as encoded by UBX (in
  24  * UBX-RXM-SFRBX messages).
  25  *
  26  * UBX encodes the 30 bit words of GPS subframes as 32 bit words in little-endian.
  27  *
  28  * The two most significant bits of the 32 bit word can be ignored.
  29  *
  30  * UBX takes care of the word parity checks. So, parity checks do not have to be
  31  * repeated for dissection. UBX inverts the bits of a word if the least
  32  * significant parity bit (D30) of the previous word is 1 (i.e. UBX undoes the
  33  * bit inverting of GPS removing the need to do so for dissection).
  34  */
  35
  36 /*
  37  * mapping from L2 channel code ID to description
  38  * see IS-GPS-200N, Section 20.3.3.3.1.2
  39  */
  40 static const value_string L2_CHANNEL_CODE[] = {
  41     {0x0, "invalid"},
  42     {0x1, "P-code ON"},
  43     {0x2, "C/A-code ON"},
  44     {0x3, "invalid"},
  45     {0, NULL},
  46 };
  47
  48 /*
  49  * mapping from URA index to URA
  50  * see IS-GPS-200N, Section 20.3.3.3.1.3
  51  */
  52 static const value_string URA_INDEX[] = {
  53     { 0,    "0.00 < URA <= 2.40"},
  54     { 1,    "2.40 < URA <= 3.40"},
  55     { 2,    "3.40 < URA <= 4.85"},
  56     { 3,    "4.85 < URA <= 6.85"},
  57     { 4,    "6.85 < URA <= 9.65"},
  58     { 5,    "9.65 < URA <= 13.65"},
  59     { 6,   "13.65 < URA <= 24.00"},
  60     { 7,   "24.00 < URA <= 48.00"},
  61     { 8,   "48.00 < URA <= 96.00"},
  62     { 9,   "96.00 < URA <= 192.00"},
  63     {10,  "192.00 < URA <= 384.00"},
  64     {11,  "384.00 < URA <= 768.00"},
  65     {12,  "768.00 < URA <= 1536.00"},
  66     {13, "1536.00 < URA <= 3072.00"},
  67     {14, "3072.00 < URA <= 6144.00"},
  68     {15, "6144.00 < URA"},
  69     {0, NULL},
  70 };
  71
  72 /*
  73  * mapping for SV health summary
  74  * see IS-GPS-200N, Section 20.3.3.3.1.4
  75  */
  76 static const value_string SV_HEALTH_SUMMARY[] = {
  77     {0, "all LNAV data are OK"},
  78     {1, "some or all LNAV data are bad"},
  79     {0, NULL},
  80 };
  81
  82 /*
  83  * mapping for codes for health of SV signal components
  84  * see IS-GPS-200N, Section 20.3.3.5.1.3
  85  */
  86 static const value_string SV_HEALTH_CODE[] = {
  87     {0,  "All Signals OK"},
  88     {1,  "All Signals Weak"},
  89     {2,  "All Signals Dead"},
  90     {3,  "All Signals Have No Data Modulation"},
  91     {4,  "L1 P Signal Weak"},
  92     {5,  "L1 P Signal Dead"},
  93     {6,  "L1 P Signal Has No Data Modulation"},
  94     {7,  "L2 P Signal Weak"},
  95     {8,  "L2 P Signal Dead"},
  96     {9,  "L2 P Signal Has No Data Modulation"},
  97     {10, "L1C Signal Weak"},
  98     {11, "L1C Signal Dead"},
  99     {12, "L1C Signal Has No Data Modulation"},
 100     {13, "L2C Signal Weak"},
 101     {14, "L2C Signal Dead"},
 102     {15, "L2C Signal Has No Data Modulation"},
 103     {16, "L1 & L2 P Signal Weak"},
 104     {17, "L1 & L2 P Signal Dead"},
 105     {18, "L1 & L2 P Signal Has No Data Modulation"},
 106     {19, "L1 & L2C Signal Weak"},
 107     {20, "L1 & L2C Signal Dead"},
 108     {21, "L1 & L2C Signal Has No Data Modulation"},
 109     {22, "L1 Signal Weak"},
 110     {23, "L1 Signal Dead"},
 111     {24, "L1 Signal Has No Data Modulation"},
 112     {25, "L2 Signal Weak"},
 113     {26, "L2 Signal Dead"},
 114     {27, "L2 Signal Has No Data Modulation"},
 115     {28, "SV Is Temporarily Out (Do not use this SV during current pass)"},
 116     {29, "SV Will Be Temporarily Out (Use with caution)"},
 117     {30, "One Or More Signals Are Deformed, However The Relevant URA Parameters Are Valid"},
 118     {31, "More Than One Combination Would Be Required To Describe Anomalies"},
 119     {0, NULL},
 120 };
 121
 122 // Initialize the protocol and registered fields
 123 static int proto_ubx_gps_l1;
 124
 125 // Telemetry Word (see IS-GPS-200N, Section 20.3.3.1)
 126 static int hf_ubx_gps_l1_tlm_preamble;
 127 static int hf_ubx_gps_l1_tlm_message;
 128 static int hf_ubx_gps_l1_tlm_integrity;
 129 static int hf_ubx_gps_l1_tlm_reserved;
 130 static int hf_ubx_gps_l1_tlm_parity;
 131
 132 // Handover Word (see IS-GPS-200N, Section 20.3.3.2)
 133 static int hf_ubx_gps_l1_how_tow_count;
 134 static int hf_ubx_gps_l1_how_alert;
 135 static int hf_ubx_gps_l1_how_anti_spoof;
 136 static int hf_ubx_gps_l1_how_subframe_id;
 137 static int hf_ubx_gps_l1_how_parity_sol;
 138 static int hf_ubx_gps_l1_how_parity;
 139
 140 // Subframe 1 (see IS-GPS-200N, Section 20.3.3.3)
 141 static int hf_ubx_gps_l1_sf1;
 142 static int hf_ubx_gps_l1_sf1_week_no;
 143 static int hf_ubx_gps_l1_sf1_l2_channel_code;
 144 static int hf_ubx_gps_l1_sf1_ura_index;
 145 static int hf_ubx_gps_l1_sf1_sv_health_summary;
 146 static int hf_ubx_gps_l1_sf1_sv_health;
 147 static int hf_ubx_gps_l1_sf1_iodc_msbs;
 148 static int hf_ubx_gps_l1_sf1_w3_parity;
 149 static int hf_ubx_gps_l1_sf1_w4_l2_p_data_flag;
 150 static int hf_ubx_gps_l1_sf1_w4_reserved;
 151 static int hf_ubx_gps_l1_sf1_w4_parity;
 152 static int hf_ubx_gps_l1_sf1_w5_reserved;
 153 static int hf_ubx_gps_l1_sf1_w5_parity;
 154 static int hf_ubx_gps_l1_sf1_w6_reserved;
 155 static int hf_ubx_gps_l1_sf1_w6_parity;
 156 static int hf_ubx_gps_l1_sf1_w7_reserved;
 157 static int hf_ubx_gps_l1_sf1_w7_tgd;
 158 static int hf_ubx_gps_l1_sf1_w7_parity;
 159 static int hf_ubx_gps_l1_sf1_w8_iodc_lsbs;
 160 static int hf_ubx_gps_l1_sf1_w8_toc;
 161 static int hf_ubx_gps_l1_sf1_w8_parity;
 162 static int hf_ubx_gps_l1_sf1_w9_af2;
 163 static int hf_ubx_gps_l1_sf1_w9_af1;
 164 static int hf_ubx_gps_l1_sf1_w9_parity;
 165 static int hf_ubx_gps_l1_sf1_w10_af0;
 166 static int hf_ubx_gps_l1_sf1_w10_parity;
 167
 168 static dissector_table_t ubx_gps_l1_sf_dissector_table;
 169
 170 static expert_field ei_ubx_gps_l1_tlm_preamble;
 171 static expert_field ei_ubx_gps_l1_how_tow_count;
 172 static expert_field ei_ubx_gps_l1_how_subframe_id;
 173
 174 static int ett_ubx_gps_l1;
 175 static int ett_ubx_gps_l1_tlm;
 176 static int ett_ubx_gps_l1_how;
 177 static int ett_ubx_gps_l1_sf1_w3;
 178 static int ett_ubx_gps_l1_sf1_w4;
 179 static int ett_ubx_gps_l1_sf1_w5;
 180 static int ett_ubx_gps_l1_sf1_w6;
 181 static int ett_ubx_gps_l1_sf1_w7;
 182 static int ett_ubx_gps_l1_sf1_w8;
 183 static int ett_ubx_gps_l1_sf1_w9;
 184 static int ett_ubx_gps_l1_sf1_w10;
 185
 186 /* Format TOW count */
 187 static void fmt_tow_count(char *label, int32_t c) {
 188     unsigned tow = c << 2;
 189     snprintf(label, ITEM_LABEL_LENGTH, "%d (TOW: %.1fs)", c, tow * 1.5);
 190 }
 191
 192 /* Format Clock Data Reference Time t_OC */
 193 static void fmt_t_oc(char *label, int32_t i) {
 194     unsigned t_oc = i << 4;
 195     snprintf(label, ITEM_LABEL_LENGTH, "%ds", t_oc);
 196 }
 197
 198 /* Dissect GPS L1 C/A LNAV navigation message */
 199 static int dissect_ubx_gps_l1(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_) {
 200     uint32_t subframe_id = (tvb_get_uint32(tvb, 4, ENC_LITTLE_ENDIAN) & 0x00000700) >> 8;
 201
 202     col_set_str(pinfo->cinfo, COL_PROTOCOL, "GPS L1 LNAV");
 203     col_clear(pinfo->cinfo, COL_INFO);
 204     col_append_fstr(pinfo->cinfo, COL_INFO, "Subframe %i", subframe_id);
 205
 206     proto_tree *gps_l1_tree = proto_tree_add_subtree_format(tree, tvb, 0, 40, ett_ubx_gps_l1, NULL, "GPS L1 LNAV (Subframe %i)", subframe_id);
 207
 208     // send the subframe to the next dissector
 209     if (!dissector_try_uint(ubx_gps_l1_sf_dissector_table, subframe_id, tvb, pinfo, gps_l1_tree)) {
 210         call_data_dissector(tvb, pinfo, tree);
 211     }
 212
 213     return tvb_captured_length(tvb);
 214 }
 215
 216 // Dissect the telemetry (TLM) word
 217 static void dissect_ubx_gps_l1_tlm(tvbuff_t *tvb, packet_info *pinfo _U_, proto_tree *tree, void *data _U_) {
 218     proto_tree *tlm_tree = proto_tree_add_subtree_format(tree, tvb, 0, 4, ett_ubx_gps_l1_tlm, NULL, "Word 1: Telemetry");
 219
 220     uint32_t tlm_preamble;
 221     proto_item* pi_tlm_preamble = proto_tree_add_item_ret_uint(tlm_tree, hf_ubx_gps_l1_tlm_preamble, tvb, 0, 4, ENC_LITTLE_ENDIAN, &tlm_preamble);
 222     if (tlm_preamble != 0x8b) {
 223         expert_add_info_format(pinfo, pi_tlm_preamble, &ei_ubx_gps_l1_tlm_preamble, "Invalid preamble");
 224     }
 225
 226     proto_tree_add_item(tlm_tree, hf_ubx_gps_l1_tlm_message,   tvb, 0, 4, ENC_LITTLE_ENDIAN);
 227     proto_tree_add_item(tlm_tree, hf_ubx_gps_l1_tlm_integrity, tvb, 0, 4, ENC_LITTLE_ENDIAN);
 228     proto_tree_add_item(tlm_tree, hf_ubx_gps_l1_tlm_reserved,  tvb, 0, 4, ENC_LITTLE_ENDIAN);
 229     proto_tree_add_item(tlm_tree, hf_ubx_gps_l1_tlm_parity,    tvb, 0, 4, ENC_LITTLE_ENDIAN);
 230 }
 231
 232 // Dissect the handover word (HOW)
 233 static void dissect_ubx_gps_l1_how(tvbuff_t *tvb, packet_info *pinfo _U_, proto_tree *tree, void *data _U_) {
 234     uint32_t subframe_id;
 235
 236     proto_tree *how_tree = proto_tree_add_subtree_format(tree, tvb, 4, 4, ett_ubx_gps_l1_how, NULL, "Word 2: Handover");
 237
 238     uint32_t tow_count;
 239     proto_item* pi_how_tow_count = proto_tree_add_item_ret_uint(how_tree, hf_ubx_gps_l1_how_tow_count, tvb, 4, 4, ENC_LITTLE_ENDIAN, &tow_count);
 240     if (tow_count > 100799) {
 241         expert_add_info_format(pinfo, pi_how_tow_count, &ei_ubx_gps_l1_how_tow_count, "Invalid TOW count");
 242     }
 243
 244     proto_tree_add_item(how_tree, hf_ubx_gps_l1_how_alert,       tvb, 4, 4, ENC_LITTLE_ENDIAN);
 245     proto_tree_add_item(how_tree, hf_ubx_gps_l1_how_anti_spoof,  tvb, 4, 4, ENC_LITTLE_ENDIAN);
 246
 247     proto_item* pi_how_sf_id = proto_tree_add_item_ret_uint(how_tree, hf_ubx_gps_l1_how_subframe_id, tvb, 4, 4, ENC_LITTLE_ENDIAN, &subframe_id);
 248     if (subframe_id > 5) {
 249         expert_add_info_format(pinfo, pi_how_sf_id, &ei_ubx_gps_l1_how_subframe_id, "Invalid subframe ID");
 250     }
 251
 252     proto_tree_add_item(how_tree, hf_ubx_gps_l1_how_parity_sol,  tvb, 4, 4, ENC_LITTLE_ENDIAN);
 253     proto_tree_add_item(how_tree, hf_ubx_gps_l1_how_parity,      tvb, 4, 4, ENC_LITTLE_ENDIAN);
 254 }
 255
 256 /* Dissect subframe 1 */
 257 static int dissect_ubx_gps_l1_sf1(tvbuff_t *tvb, packet_info *pinfo _U_, proto_tree *tree, void *data _U_) {
 258     dissect_ubx_gps_l1_tlm(tvb, pinfo, tree, data);
 259     dissect_ubx_gps_l1_how(tvb, pinfo, tree, data);
 260
 261     // subframe 1, word 3
 262     proto_tree *w3_tree = proto_tree_add_subtree_format(tree,         tvb, 8, 4, ett_ubx_gps_l1_sf1_w3, NULL, "Word 3");
 263     proto_tree_add_item(w3_tree, hf_ubx_gps_l1_sf1_week_no,           tvb, 8, 4, ENC_LITTLE_ENDIAN);
 264     proto_tree_add_item(w3_tree, hf_ubx_gps_l1_sf1_l2_channel_code,   tvb, 8, 4, ENC_LITTLE_ENDIAN);
 265     proto_tree_add_item(w3_tree, hf_ubx_gps_l1_sf1_ura_index,         tvb, 8, 4, ENC_LITTLE_ENDIAN);
 266     proto_tree_add_item(w3_tree, hf_ubx_gps_l1_sf1_sv_health_summary, tvb, 8, 4, ENC_LITTLE_ENDIAN);
 267     proto_tree_add_item(w3_tree, hf_ubx_gps_l1_sf1_sv_health,         tvb, 8, 4, ENC_LITTLE_ENDIAN);
 268     proto_tree_add_item(w3_tree, hf_ubx_gps_l1_sf1_iodc_msbs,         tvb, 8, 4, ENC_LITTLE_ENDIAN);
 269     proto_tree_add_item(w3_tree, hf_ubx_gps_l1_sf1_w3_parity,         tvb, 8, 4, ENC_LITTLE_ENDIAN);
 270
 271     // subframe 1, word 4
 272     proto_tree *w4_tree = proto_tree_add_subtree_format(tree,         tvb, 12, 4, ett_ubx_gps_l1_sf1_w4, NULL, "Word 4");
 273     proto_tree_add_item(w4_tree, hf_ubx_gps_l1_sf1_w4_l2_p_data_flag, tvb, 12, 4, ENC_LITTLE_ENDIAN);
 274     proto_tree_add_item(w4_tree, hf_ubx_gps_l1_sf1_w4_reserved,       tvb, 12, 4, ENC_LITTLE_ENDIAN);
 275     proto_tree_add_item(w4_tree, hf_ubx_gps_l1_sf1_w4_parity,         tvb, 12, 4, ENC_LITTLE_ENDIAN);
 276
 277
 278     // subframe 1, word 5
 279     proto_tree *w5_tree = proto_tree_add_subtree_format(tree,   tvb, 16, 4, ett_ubx_gps_l1_sf1_w5, NULL, "Word 5");
 280     proto_tree_add_item(w5_tree, hf_ubx_gps_l1_sf1_w5_reserved, tvb, 16, 4, ENC_LITTLE_ENDIAN);
 281     proto_tree_add_item(w5_tree, hf_ubx_gps_l1_sf1_w5_parity,   tvb, 16, 4, ENC_LITTLE_ENDIAN);
 282
 283     // subframe 1, word 6
 284     proto_tree *w6_tree = proto_tree_add_subtree_format(tree,   tvb, 20, 4, ett_ubx_gps_l1_sf1_w6, NULL, "Word 6");
 285     proto_tree_add_item(w6_tree, hf_ubx_gps_l1_sf1_w6_reserved, tvb, 20, 4, ENC_LITTLE_ENDIAN);
 286     proto_tree_add_item(w6_tree, hf_ubx_gps_l1_sf1_w6_parity,   tvb, 20, 4, ENC_LITTLE_ENDIAN);
 287
 288     // subframe 1, word 7
 289     proto_tree *w7_tree = proto_tree_add_subtree_format(tree,   tvb, 24, 4, ett_ubx_gps_l1_sf1_w7, NULL, "Word 7");
 290     proto_tree_add_item(w7_tree, hf_ubx_gps_l1_sf1_w7_reserved, tvb, 24, 4, ENC_LITTLE_ENDIAN);
 291     proto_tree_add_item(w7_tree, hf_ubx_gps_l1_sf1_w7_tgd,      tvb, 24, 4, ENC_LITTLE_ENDIAN);
 292     proto_tree_add_item(w7_tree, hf_ubx_gps_l1_sf1_w7_parity,   tvb, 24, 4, ENC_LITTLE_ENDIAN);
 293
 294     // subframe 1, word 8
 295     proto_tree *w8_tree = proto_tree_add_subtree_format(tree,     tvb, 28, 4, ett_ubx_gps_l1_sf1_w8, NULL, "Word 8");
 296     proto_tree_add_item(w8_tree, hf_ubx_gps_l1_sf1_w8_iodc_lsbs,  tvb, 28, 4, ENC_LITTLE_ENDIAN);
 297     proto_tree_add_item(w8_tree, hf_ubx_gps_l1_sf1_w8_toc,        tvb, 28, 4, ENC_LITTLE_ENDIAN);
 298     proto_tree_add_item(w8_tree, hf_ubx_gps_l1_sf1_w8_parity,     tvb, 28, 4, ENC_LITTLE_ENDIAN);
 299
 300     // subframe 1, word 9
 301     proto_tree *w9_tree = proto_tree_add_subtree_format(tree, tvb, 32, 4, ett_ubx_gps_l1_sf1_w9, NULL, "Word 9");
 302     proto_tree_add_item(w9_tree, hf_ubx_gps_l1_sf1_w9_af2,    tvb, 32, 4, ENC_LITTLE_ENDIAN);
 303     proto_tree_add_item(w9_tree, hf_ubx_gps_l1_sf1_w9_af1,    tvb, 32, 4, ENC_LITTLE_ENDIAN);
 304     proto_tree_add_item(w9_tree, hf_ubx_gps_l1_sf1_w9_parity, tvb, 32, 4, ENC_LITTLE_ENDIAN);
 305
 306     // subframe 1, word 10
 307     proto_tree *w10_tree = proto_tree_add_subtree_format(tree,  tvb, 36, 4, ett_ubx_gps_l1_sf1_w10, NULL, "Word 10");
 308     proto_tree_add_item(w10_tree, hf_ubx_gps_l1_sf1_w10_af0,    tvb, 36, 4, ENC_LITTLE_ENDIAN);
 309     proto_tree_add_item(w10_tree, hf_ubx_gps_l1_sf1_w10_parity, tvb, 36, 4, ENC_LITTLE_ENDIAN);
 310
 311     return tvb_captured_length(tvb);
 312 }
 313
 314 void proto_register_ubx_gps_l1(void) {
 315
 316     static hf_register_info hf[] = {
 317         // TLM
 318         {&hf_ubx_gps_l1_tlm_preamble,    {"Preamble",                    "gps_l1.tlm.preamble",    FT_UINT32,  BASE_HEX,  NULL, 0x3fc00000, NULL, HFILL}},
 319         {&hf_ubx_gps_l1_tlm_message,     {"Message",                     "gps_l1.tlm.message",     FT_UINT32,  BASE_HEX,  NULL, 0x003fff00, NULL, HFILL}},
 320         {&hf_ubx_gps_l1_tlm_integrity,   {"Integrity Status Flag (ISF)", "gps_l1.tlm.integrity",   FT_BOOLEAN, 32,        NULL, 0x00000080, NULL, HFILL}},
 321         {&hf_ubx_gps_l1_tlm_reserved,    {"Reserved",                    "gps_l1.tlm.reserved",    FT_UINT32,  BASE_HEX,  NULL, 0x00000040, NULL, HFILL}},
 322         {&hf_ubx_gps_l1_tlm_parity,      {"Parity",                      "gps_l1.tlm.parity",      FT_UINT32,  BASE_HEX,  NULL, 0x0000003f, NULL, HFILL}},
 323
 324         // HOW
 325         {&hf_ubx_gps_l1_how_tow_count,   {"Time-of-Week (TOW) Count",    "gps_l1.how.tow_count",   FT_UINT32,  BASE_CUSTOM, CF_FUNC(&fmt_tow_count), 0x3fffe000, NULL, HFILL}},
 326         {&hf_ubx_gps_l1_how_alert,       {"Alert",                       "gps_l1.how.alert",       FT_BOOLEAN, 32,        NULL, 0x00001000, NULL, HFILL}},
 327         {&hf_ubx_gps_l1_how_anti_spoof,  {"Anti-Spoof (A-S)",            "gps_l1.how.anti_spoof",  FT_BOOLEAN, 32,        NULL, 0x00000800, NULL, HFILL}},
 328         {&hf_ubx_gps_l1_how_subframe_id, {"Subframe ID",                 "gps_l1.how.subframe_id", FT_UINT32,  BASE_DEC,  NULL, 0x00000700, NULL, HFILL}},
 329         {&hf_ubx_gps_l1_how_parity_sol,  {"Solved for parity zero bits", "gps_l1.how.parity_sol",  FT_UINT32,  BASE_HEX,  NULL, 0x000000c0, NULL, HFILL}},
 330         {&hf_ubx_gps_l1_how_parity,      {"Parity",                      "gps_l1.how.parity",      FT_UINT32,  BASE_DEC,  NULL, 0x0000003f, NULL, HFILL}},
 331
 332         // SF1
 333         {&hf_ubx_gps_l1_sf1,                   {"Subframe 1",                                 "gps_l1.sf1",                   FT_NONE,    BASE_NONE, NULL, 0x0,        NULL, HFILL}},
 334         {&hf_ubx_gps_l1_sf1_week_no,           {"Week Number",                                "gps_l1.sf1.week_number",       FT_UINT32,  BASE_DEC,  NULL, 0x3ff00000, NULL, HFILL}},
 335         {&hf_ubx_gps_l1_sf1_l2_channel_code,   {"L2 Channel Code",                            "gps_l1.sf1.l2_channel_code",   FT_UINT32,  BASE_HEX,  VALS(L2_CHANNEL_CODE), 0x000c0000, NULL, HFILL}},
 336         {&hf_ubx_gps_l1_sf1_ura_index,         {"URA Index",                                  "gps_l1.sf1.ura_index",         FT_UINT32,  BASE_HEX,  VALS(URA_INDEX), 0x0003c000, NULL, HFILL}},
 337         {&hf_ubx_gps_l1_sf1_sv_health_summary, {"SV Health Summary",                          "gps_l1.sf1.sv_health_summary", FT_UINT32,  BASE_HEX,  VALS(SV_HEALTH_SUMMARY), 0x00002000, NULL, HFILL}},
 338         {&hf_ubx_gps_l1_sf1_sv_health,         {"SV's Signal Component Health Status",        "gps_l1.sf1.sv_health",         FT_UINT32,  BASE_HEX,  VALS(SV_HEALTH_CODE), 0x00001f00, NULL, HFILL}},
 339         {&hf_ubx_gps_l1_sf1_iodc_msbs,         {"Issue of Data Clock (IODC) MSBs",            "gps_l1.sf1.iodc_msbs",         FT_UINT32,  BASE_HEX,  NULL, 0x000000c0, NULL, HFILL}},
 340         {&hf_ubx_gps_l1_sf1_w3_parity,         {"Parity",                                     "gps_l1.sf1.w3_parity",         FT_UINT32,  BASE_HEX,  NULL, 0x0000003f, NULL, HFILL}},
 341         {&hf_ubx_gps_l1_sf1_w4_l2_p_data_flag, {"L2 P Data Flag",                             "gps_l1.sf1.l2_p_data_flag",    FT_BOOLEAN, 32,        NULL, 0x20000000, NULL, HFILL}},
 342         {&hf_ubx_gps_l1_sf1_w4_reserved,       {"Reserved",                                   "gps_l1.sf1.w4_reserved",       FT_UINT32,  BASE_HEX,  NULL, 0x1fffffc0, NULL, HFILL}},
 343         {&hf_ubx_gps_l1_sf1_w4_parity,         {"Parity",                                     "gps_l1.sf1.w4_parity",         FT_UINT32,  BASE_HEX,  NULL, 0x0000003f, NULL, HFILL}},
 344         {&hf_ubx_gps_l1_sf1_w5_reserved,       {"Reserved",                                   "gps_l1.sf1.w5_reserved",       FT_UINT32,  BASE_HEX,  NULL, 0x3fffffc0, NULL, HFILL}},
 345         {&hf_ubx_gps_l1_sf1_w5_parity,         {"Parity",                                     "gps_l1.sf1.w5_parity",         FT_UINT32,  BASE_HEX,  NULL, 0x0000003f, NULL, HFILL}},
 346         {&hf_ubx_gps_l1_sf1_w6_reserved,       {"Reserved",                                   "gps_l1.sf1.w6_reserved",       FT_UINT32,  BASE_HEX,  NULL, 0x3fffffc0, NULL, HFILL}},
 347         {&hf_ubx_gps_l1_sf1_w6_parity,         {"Parity",                                     "gps_l1.sf1.w6_parity",         FT_UINT32,  BASE_HEX,  NULL, 0x0000003f, NULL, HFILL}},
 348         {&hf_ubx_gps_l1_sf1_w7_reserved,       {"Reserved",                                   "gps_l1.sf1.w7_reserved",       FT_UINT32,  BASE_HEX,  NULL, 0x3fffc000, NULL, HFILL}},
 349         {&hf_ubx_gps_l1_sf1_w7_tgd,            {"Estimated Group Delay Differential T_GD",    "gps_l1.sf1.w7_tgd",            FT_INT32,   BASE_DEC,  NULL, 0x00003fc0, NULL, HFILL}},
 350         {&hf_ubx_gps_l1_sf1_w7_parity,         {"Parity",                                     "gps_l1.sf1.w7_parity",         FT_UINT32,  BASE_HEX,  NULL, 0x0000003f, NULL, HFILL}},
 351         {&hf_ubx_gps_l1_sf1_w8_iodc_lsbs,      {"Issue of Data Clock (IODC) LSBs",            "gps_l1.sf1.w8_iodc_lsbs",      FT_UINT32,  BASE_HEX,  NULL, 0x3fc00000, NULL, HFILL}},
 352         {&hf_ubx_gps_l1_sf1_w8_toc,            {"Clock Data Reference Time t_OC",             "gps_l1.sf1.w8_toc",            FT_UINT32,  BASE_CUSTOM, CF_FUNC(&fmt_t_oc), 0x003fffc0, NULL, HFILL}},
 353         {&hf_ubx_gps_l1_sf1_w8_parity,         {"Parity",                                     "gps_l1.sf1.w8_parity",         FT_UINT32,  BASE_HEX,  NULL, 0x0000003f, NULL, HFILL}},
 354         {&hf_ubx_gps_l1_sf1_w9_af2,            {"Drift Rate Correction Coefficient a_f2",     "gps_l1.sf1.w9_af2",            FT_INT32,   BASE_DEC,  NULL, 0x3fc00000, NULL, HFILL}},
 355         {&hf_ubx_gps_l1_sf1_w9_af1,            {"SV Clock Drift Correction Coefficient a_f1", "gps_l1.sf1.w9_af1",            FT_INT32,   BASE_DEC,  NULL, 0x003fffc0, NULL, HFILL}},
 356         {&hf_ubx_gps_l1_sf1_w9_parity,         {"Parity",                                     "gps_l1.sf1.w9_parity",         FT_UINT32,  BASE_HEX,  NULL, 0x0000003f, NULL, HFILL}},
 357         {&hf_ubx_gps_l1_sf1_w10_af0,           {"SV Clock Bias Correction Coefficient a_f0",  "gps_l1.sf1.w10_af0",           FT_INT32,   BASE_DEC,  NULL, 0x3fffffc0, NULL, HFILL}},
 358         {&hf_ubx_gps_l1_sf1_w10_parity,        {"Parity",                                     "gps_l1.sf1.w10_parity",        FT_UINT32,  BASE_HEX,  NULL, 0x0000003f, NULL, HFILL}},
 359     };
 360
 361     expert_module_t *expert_ubx_gps_l1;
 362
 363     static ei_register_info ei[] = {
 364         {&ei_ubx_gps_l1_tlm_preamble,    {"gps_l1.tlm.preamble",    PI_PROTOCOL, PI_WARN, "Illegal preamble",    EXPFILL}},
 365         {&ei_ubx_gps_l1_how_tow_count,   {"gps_l1.how.tow_count",   PI_PROTOCOL, PI_WARN, "Illegal TOW count",   EXPFILL}},
 366         {&ei_ubx_gps_l1_how_subframe_id, {"gps_l1.how.subframe_id", PI_PROTOCOL, PI_WARN, "Illegal subframe ID", EXPFILL}},
 367     };
 368
 369     static int *ett[] = {
 370         &ett_ubx_gps_l1,
 371         &ett_ubx_gps_l1_tlm,
 372         &ett_ubx_gps_l1_how,
 373         &ett_ubx_gps_l1_sf1_w3,
 374         &ett_ubx_gps_l1_sf1_w4,
 375         &ett_ubx_gps_l1_sf1_w5,
 376         &ett_ubx_gps_l1_sf1_w6,
 377         &ett_ubx_gps_l1_sf1_w7,
 378         &ett_ubx_gps_l1_sf1_w8,
 379         &ett_ubx_gps_l1_sf1_w9,
 380         &ett_ubx_gps_l1_sf1_w10,
 381     };
 382
 383     proto_ubx_gps_l1 = proto_register_protocol("GPS L1 Navigation Message", "GPS L1", "gps_l1");
 384
 385     register_dissector("ubx_gps_l1", dissect_ubx_gps_l1, proto_ubx_gps_l1);
 386
 387     proto_register_field_array(proto_ubx_gps_l1, hf, array_length(hf));
 388     proto_register_subtree_array(ett, array_length(ett));
 389
 390     expert_ubx_gps_l1 = expert_register_protocol(proto_ubx_gps_l1);
 391     expert_register_field_array(expert_ubx_gps_l1, ei, array_length(ei));
 392
 393     ubx_gps_l1_sf_dissector_table = register_dissector_table("ubx.rxm.sfrbx.gps_l1.sf",
 394             "GPS L1 LNAV Subframe", proto_ubx_gps_l1, FT_UINT8, BASE_DEC);
 395 }
 396
 397 void proto_reg_handoff_ubx_gps_l1(void) {
 398     dissector_add_uint("ubx.rxm.sfrbx.gnssid", GNSS_ID_GPS,
 399             create_dissector_handle(dissect_ubx_gps_l1, proto_ubx_gps_l1));
 400
 401     dissector_add_uint("ubx.rxm.sfrbx.gps_l1.sf", 1,
 402             create_dissector_handle(dissect_ubx_gps_l1_sf1, proto_ubx_gps_l1));
 403 }