/*****************************************************************************
This is a decoder for RTCM-104, an obscure and complicated serial
protocol used for broadcasting pseudorange corrections from
differential-GPS reference stations. The applicable
standard is
RTCM RECOMMENDED STANDARDS FOR DIFFERENTIAL NAVSTAR GPS SERVICE,
RTCM PAPER 194-93/SC 104-STD
Ordering instructions are accessible from <http://www.rtcm.org/>
under "Publications".
Also applicable is ITU-R M.823: "Technical characteristics of
differential transmissions for global navigation satellite systems
from maritime radio beacons in the frequency band 283.5 - 315 kHz in
region 1 and 285 - 325 kHz in regions 2 & 3."
The RTCM protocol uses as a transport layer the GPS satellite downlink
protocol described in IS-GPS-200, the Navstar GPS Interface
Specification. This code relies on the lower-level packet-assembly
code for that protocol in isgps.c.
The lower layer's job is done when it has assembled a message of up to
33 words of clean parity-checked data. At this point this upper layer
takes over. struct rtcm_msg_t is overlaid on the buffer and the bitfields
are used to extract pieces of it. Those pieces are copied and (where
necessary) reassembled into a struct rtcm_t.
This code and the contents of isgps.c are evolved from code by Wolgang
Rupprecht. Wolfgang's decoder was loosely based on one written by
John Sager in 1999 (in particular the dump function emits a close
descendant of Sager's dump format). Here are John Sager's original
notes:
The RTCM decoder prints a legible representation of the input data.
The RTCM SC-104 specification is copyrighted, so I cannot
quote it - in fact, I have never read it! Most of the information
used to develop the decoder came from publication ITU-R M.823.
This is a specification of the data transmitted from LF DGPS
beacons in the 300kHz band. M.823 contains most of those parts of
RTCM SC-104 directly relevant to the air interface (there
are one or two annoying and vital omissions!). Information
about the serial interface format was gleaned from studying
the output of a beacon receiver test program made available on
Starlink's website.
*****************************************************************************/
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#include <stdio.h>
#include <math.h> /* for round() */
#include "gpsd.h"
#ifdef RTCM104_ENABLE
/*
* Structures for interpreting words in an RTCM-104 message (after
* parity checking and removing inversion).
*
* The RTCM standard is less explicit than it should be about signed-integer
* representations. Two's compliment is specified for prc and rrc (msg1wX),
* but not everywhere.
*/
#define ZCOUNT_SCALE 0.6 /* sec */
#define PCSMALL 0.02 /* meters */
#define PCLARGE 0.32 /* meters */
#define RRSMALL 0.002 /* meters/sec */
#define RRLARGE 0.032 /* meters/sec */
#define MAXPCSMALL (0x7FFF * PCSMALL) /* 16-bits signed */
#define MAXRRSMALL (0x7F * RRSMALL) /* 8-bits signed */
#define XYZ_SCALE 0.01 /* meters */
#define DXYZ_SCALE 0.1 /* meters */
#define LA_SCALE (90.0/32767.0) /* degrees */
#define LO_SCALE (180.0/32767.0) /* degrees */
#define FREQ_SCALE 0.1 /* kHz */
#define FREQ_OFFSET 190.0 /* kHz */
#define CNR_OFFSET 24 /* dB */
#define TU_SCALE 5 /* minutes */
#pragma pack(1)
#ifndef WORDS_BIGENDIAN /* little-endian, like x86 */
struct rtcm_msg_t {
struct rtcm_msghw1 { /* header word 1 */
uint parity:6;
uint refstaid:10; /* reference station ID */
uint msgtype:6; /* RTCM message type */
uint preamble:8; /* fixed at 01100110 */
uint _pad:2;
} w1;
struct rtcm_msghw2 { /* header word 2 */
uint parity:6;
uint stathlth:3; /* station health */
uint frmlen:5;
uint sqnum:3;
uint zcnt:13;
uint _pad:2;
} w2;
union {
/* msg 1 - differential gps corrections */
struct rtcm_msg1 {
struct b_correction_t {
struct { /* msg 1 word 3 */
uint parity:6;
int pc1:16;
uint satident1:5; /* satellite ID */
uint udre1:2;
uint scale1:1;
uint _pad:2;
} w3;
struct { /* msg 1 word 4 */
uint parity:6;
uint satident2:5; /* satellite ID */
uint udre2:2;
uint scale2:1;
uint issuedata1:8;
int rangerate1:8;
uint _pad:2;
} w4;
struct { /* msg 1 word 5 */
uint parity:6;
int rangerate2:8;
int pc2:16;
uint _pad:2;
} w5;
struct { /* msg 1 word 6 */
uint parity:6;
int pc3_h:8;
uint satident3:5; /* satellite ID */
uint udre3:2;
uint scale3:1;
uint issuedata2:8;
uint _pad:2;
} w6;
struct { /* msg 1 word 7 */
uint parity:6;
uint issuedata3:8;
int rangerate3:8;
uint pc3_l:8; /* NOTE: uint for low byte */
uint _pad:2;
} w7;
} corrections[(RTCM_WORDS_MAX - 2) / 5];
} type1;
/* msg 3 - reference station parameters */
struct rtcm_msg3 {
struct {
uint parity:6;
uint x_h:24;
uint _pad:2;
} w3;
struct {
uint parity:6;
uint y_h:16;
uint x_l:8;
uint _pad:2;
} w4;
struct {
uint parity:6;
uint z_h:8;
uint y_l:16;
uint _pad:2;
} w5;
struct {
uint parity:6;
uint z_l:24;
uint _pad:2;
} w6;
} type3;
/* msg 4 - reference station datum */
struct rtcm_msg4 {
struct {
uint parity:6;
uint datum_alpha_char2:8;
uint datum_alpha_char1:8;
uint spare:4;
uint dat:1;
uint dgnss:3;
uint _pad:2;
} w3;
struct {
uint parity:6;
uint datum_sub_div_char2:8;
uint datum_sub_div_char1:8;
uint datum_sub_div_char3:8;
uint _pad:2;
} w4;
struct {
uint parity:6;
uint dy_h:8;
uint dx:16;
uint _pad:2;
} w5;
struct {
uint parity:6;
uint dz:24;
uint dy_l:8;
uint _pad:2;
} w6;
} type4;
/* msg 5 - constellation health */
struct rtcm_msg5 {
struct b_health_t {
uint parity:6;
uint unassigned:2;
uint time_unhealthy:4;
uint loss_warn:1;
uint new_nav_data:1;
uint health_enable:1;
uint cn0:5;
uint data_health:3;
uint issue_of_data_link:1;
uint sat_id:5;
uint reserved:1;
uint _pad:2;
} health[MAXHEALTH];
} type5;
/* msg 6 - null message */
/* msg 7 - beacon almanac */
struct rtcm_msg7 {
struct b_station_t {
struct {
uint parity:6;
int lon_h:8;
int lat:16;
uint _pad:2;
} w3;
struct {
uint parity:6;
uint freq_h:6;
uint range:10;
uint lon_l:8;
uint _pad:2;
} w4;
struct {
uint parity:6;
uint encoding:1;
uint sync_type:1;
uint mod_mode:1;
uint bit_rate:3;
/*
* ITU-R M.823-2 page 9 and RTCM-SC104 v2.1 pages
* 4-21 and 4-22 are in conflict over the next two
* field sizes. ITU says 9+3, RTCM says 10+2.
* The latter correctly decodes the USCG station
* id's so I'll use that one here. -wsr
*/
uint station_id:10;
uint health:2;
uint freq_l:6;
uint _pad:2;
} w5;
} almanac[(RTCM_WORDS_MAX - 2)/3];
} type7;
/* msg 16 - text msg */
struct rtcm_msg16 {
struct {
uint parity:6;
uint byte3:8;
uint byte2:8;
uint byte1:8;
uint _pad:2;
} txt[RTCM_WORDS_MAX-2];
} type16;
/* unknown message */
isgps30bits_t rtcm_msgunk[RTCM_WORDS_MAX-2];
} msg_type;
};
#endif /* LITTLE_ENDIAN */
#if WORDS_BIGENDIAN
/* This struct was generated from the above using invert-bitfields.pl */
#ifndef S_SPLINT_S /* splint thinks it's a duplicate definition */
struct rtcm_msg_t {
struct rtcm_msghw1 { /* header word 1 */
uint _pad:2;
uint preamble:8; /* fixed at 01100110 */
uint msgtype:6; /* RTCM message type */
uint refstaid:10; /* reference station ID */
uint parity:6;
} w1;
struct rtcm_msghw2 { /* header word 2 */
uint _pad:2;
uint zcnt:13;
uint sqnum:3;
uint frmlen:5;
uint stathlth:3; /* station health */
uint parity:6;
} w2;
union {
/* msg 1 - differential gps corrections */
struct rtcm_msg1 {
struct b_correction_t {
struct { /* msg 1 word 3 */
uint _pad:2;
uint scale1:1;
uint udre1:2;
uint satident1:5; /* satellite ID */
int pc1:16;
uint parity:6;
} w3;
struct { /* msg 1 word 4 */
uint _pad:2;
int rangerate1:8;
uint issuedata1:8;
uint scale2:1;
uint udre2:2;
uint satident2:5; /* satellite ID */
uint parity:6;
} w4;
struct { /* msg 1 word 5 */
uint _pad:2;
int pc2:16;
int rangerate2:8;
uint parity:6;
} w5;
struct { /* msg 1 word 6 */
uint _pad:2;
uint issuedata2:8;
uint scale3:1;
uint udre3:2;
uint satident3:5; /* satellite ID */
int pc3_h:8;
uint parity:6;
} w6;
struct { /* msg 1 word 7 */
uint _pad:2;
uint pc3_l:8; /* NOTE: uint for low byte */
int rangerate3:8;
uint issuedata3:8;
uint parity:6;
} w7;
} corrections[(RTCM_WORDS_MAX - 2) / 5];
} type1;
/* msg 3 - reference station parameters */
struct rtcm_msg3 {
struct {
uint _pad:2;
uint x_h:24;
uint parity:6;
} w3;
struct {
uint _pad:2;
uint x_l:8;
uint y_h:16;
uint parity:6;
} w4;
struct {
uint _pad:2;
uint y_l:16;
uint z_h:8;
uint parity:6;
} w5;
struct {
uint _pad:2;
uint z_l:24;
uint parity:6;
} w6;
} type3;
/* msg 4 - reference station datum */
struct rtcm_msg4 {
struct {
uint _pad:2;
uint dgnss:3;
uint dat:1;
uint spare:4;
uint datum_alpha_char1:8;
uint datum_alpha_char2:8;
uint parity:6;
} w3;
struct {
uint _pad:2;
uint datum_sub_div_char3:8;
uint datum_sub_div_char1:8;
uint datum_sub_div_char2:8;
uint parity:6;
} w4;
struct {
uint _pad:2;
uint dx:16;
uint dy_h:8;
uint parity:6;
} w5;
struct {
uint _pad:2;
uint dy_l:8;
uint dz:24;
uint parity:6;
} w6;
} type4;
/* msg 5 - constellation health */
struct rtcm_msg5 {
struct b_health_t {
uint _pad:2;
uint reserved:1;
uint sat_id:5;
uint issue_of_data_link:1;
uint data_health:3;
uint cn0:5;
uint health_enable:1;
uint new_nav_data:1;
uint loss_warn:1;
uint time_unhealthy:4;
uint unassigned:2;
uint parity:6;
} health[MAXHEALTH];
} type5;
/* msg 6 - null message */
/* msg 7 - beacon almanac */
struct rtcm_msg7 {
struct b_station_t {
struct {
uint _pad:2;
int lat:16;
int lon_h:8;
uint parity:6;
} w3;
struct {
uint _pad:2;
uint lon_l:8;
uint range:10;
uint freq_h:6;
uint parity:6;
} w4;
struct {
uint _pad:2;
uint freq_l:6;
uint health:2;
uint station_id:10;
/* see comments in LE struct above. */
uint bit_rate:3;
uint mod_mode:1;
uint sync_type:1;
uint encoding:1;
uint parity:6;
} w5;
} almanac[(RTCM_WORDS_MAX - 2)/3];
} type7;
/* msg 16 - text msg */
struct rtcm_msg16 {
struct {
uint _pad:2;
uint byte1:8;
uint byte2:8;
uint byte3:8;
uint parity:6;
} txt[RTCM_WORDS_MAX-2];
} type16;
/* unknown message */
isgps30bits_t rtcm_msgunk[RTCM_WORDS_MAX-2];
} msg_type;
};
#endif /* S_SPLINT_S */
#endif /* BIG ENDIAN */
static unsigned int tx_speed[] = { 25, 50, 100, 110, 150, 200, 250, 300 };
void rtcm_unpack(struct gps_device_t *session)
/* break out the raw bits into the content fields */
{
int len;
unsigned int n, w;
struct rtcm_t *tp = &session->gpsdata.rtcm;
struct rtcm_msg_t *msg = (struct rtcm_msg_t *)session->driver.isgps.buf;
tp->type = msg->w1.msgtype;
tp->length = msg->w2.frmlen;
tp->zcount = msg->w2.zcnt * ZCOUNT_SCALE;
tp->refstaid = msg->w1.refstaid;
tp->seqnum = msg->w2.sqnum;
tp->stathlth = msg->w2.stathlth;
len = (int)tp->length;
n = 0;
switch (tp->type) {
case 1:
case 9:
{
struct b_correction_t *m = &msg->msg_type.type1.corrections[0];
while (len >= 0) {
if (len >= 2) {
tp->msg_data.ranges.sat[n].ident = m->w3.satident1;
tp->msg_data.ranges.sat[n].udre = m->w3.udre1;
tp->msg_data.ranges.sat[n].issuedata = m->w4.issuedata1;
tp->msg_data.ranges.sat[n].rangerr = m->w3.pc1 *
(m->w3.scale1 ? PCLARGE : PCSMALL);
tp->msg_data.ranges.sat[n].rangerate = m->w4.rangerate1 *
(m->w3.scale1 ? RRLARGE : RRSMALL);
n++;
}
if (len >= 4) {
tp->msg_data.ranges.sat[n].ident = m->w4.satident2;
tp->msg_data.ranges.sat[n].udre = m->w4.udre2;
tp->msg_data.ranges.sat[n].issuedata = m->w6.issuedata2;
tp->msg_data.ranges.sat[n].rangerr = m->w5.pc2 *
(m->w4.scale2 ? PCLARGE : PCSMALL);
tp->msg_data.ranges.sat[n].rangerate = m->w5.rangerate2 *
(m->w4.scale2 ? RRLARGE : RRSMALL);
n++;
}
if (len >= 5) {
tp->msg_data.ranges.sat[n].ident = m->w6.satident3;
tp->msg_data.ranges.sat[n].udre = m->w6.udre3;
tp->msg_data.ranges.sat[n].issuedata = m->w7.issuedata3;
/*@ -shiftimplementation @*/
tp->msg_data.ranges.sat[n].rangerr = ((m->w6.pc3_h<<8)|(m->w7.pc3_l)) *
(m->w6.scale3 ? PCLARGE : PCSMALL);
tp->msg_data.ranges.sat[n].rangerate = m->w7.rangerate3 *
(m->w6.scale3 ? RRLARGE : RRSMALL);
/*@ +shiftimplementation @*/
n++;
}
len -= 5;
m++;
}
tp->msg_data.ranges.nentries = n;
}
break;
case 3:
{
struct rtcm_msg3 *m = &msg->msg_type.type3;
if ((tp->msg_data.ecef.valid = len >= 4)) {
tp->msg_data.ecef.x = ((m->w3.x_h<<8)|(m->w4.x_l))*XYZ_SCALE;
tp->msg_data.ecef.y = ((m->w4.y_h<<16)|(m->w5.y_l))*XYZ_SCALE;
tp->msg_data.ecef.z = ((m->w5.z_h<<24)|(m->w6.z_l))*XYZ_SCALE;
}
}
break;
case 4:
if ((tp->msg_data.reference.valid = len >= 2)){
struct rtcm_msg4 *m = &msg->msg_type.type4;
tp->msg_data.reference.system =
(m->w3.dgnss==0) ? gps :
((m->w3.dgnss==1) ? glonass : unknown);
tp->msg_data.reference.sense = (m->w3.dat != 0) ? global : local;
if (m->w3.datum_alpha_char1){
tp->msg_data.reference.datum[n++] = (char)(m->w3.datum_alpha_char1);
}
if (m->w3.datum_alpha_char2){
tp->msg_data.reference.datum[n++] = (char)(m->w3.datum_alpha_char2);
}
if (m->w4.datum_sub_div_char1){
tp->msg_data.reference.datum[n++] = (char)(m->w4.datum_sub_div_char1);
}
if (m->w4.datum_sub_div_char2){
tp->msg_data.reference.datum[n++] = (char)(m->w4.datum_sub_div_char2);
}
if (m->w4.datum_sub_div_char3){
tp->msg_data.reference.datum[n++] = (char)(m->w4.datum_sub_div_char3);
}
tp->msg_data.reference.datum[n++] = '\0';
if (len >= 4) {
tp->msg_data.reference.dx = m->w5.dx * DXYZ_SCALE;
tp->msg_data.reference.dy = ((m->w5.dy_h << 8) | m->w6.dy_l) * DXYZ_SCALE;
tp->msg_data.reference.dz = m->w6.dz * DXYZ_SCALE;
} else
tp->msg_data.reference.sense = invalid;
}
break;
case 5:
for (n = 0; n < (unsigned)len; n++) {
struct consat_t *csp = &tp->msg_data.conhealth.sat[n];
struct b_health_t *m = &msg->msg_type.type5.health[n];
csp->ident = m->sat_id;
csp->iodl = m->issue_of_data_link!=0;
csp->health = m->data_health;
/*@i@*/csp->snr = (m->cn0?(m->cn0+CNR_OFFSET):SNR_BAD);
csp->health_en = m->health_enable;
csp->new_data = m->new_nav_data!=0;
csp->los_warning = m->loss_warn!=0;
csp->tou = m->time_unhealthy*TU_SCALE;
}
tp->msg_data.conhealth.nentries = n;
break;
case 7:
for (w = 0; w < (unsigned)len; w++) {
struct station_t *np = &tp->msg_data.almanac.station[n];
struct b_station_t *mp = &msg->msg_type.type7.almanac[w];
np->latitude = mp->w3.lat * LA_SCALE;
/*@i@*/np->longitude = ((mp->w3.lon_h << 8) | mp->w4.lon_l) * LO_SCALE;
np->range = mp->w4.range;
np->frequency = (((mp->w4.freq_h << 6) | mp->w5.freq_l) * FREQ_SCALE) + FREQ_OFFSET;
np->health = mp->w5.health;
np->station_id = mp->w5.station_id,
np->bitrate = tx_speed[mp->w5.bit_rate];
n++;
}
tp->msg_data.almanac.nentries = (unsigned)(len/3);
break;
case 16:
/*@ -boolops @*/
for (w = 0; w < (unsigned)len; w++){
if (!msg->msg_type.type16.txt[w].byte1) {
break;
}
tp->msg_data.message[n++] = (char)(msg->msg_type.type16.txt[w].byte1);
if (!msg->msg_type.type16.txt[w].byte2) {
break;
}
tp->msg_data.message[n++] = (char)(msg->msg_type.type16.txt[w].byte2);
if (!msg->msg_type.type16.txt[w].byte3) {
break;
}
tp->msg_data.message[n++] = (char)(msg->msg_type.type16.txt[w].byte3);
}
/*@ +boolops @*/
tp->msg_data.message[n++] = '\0';
break;
default:
memcpy(tp->msg_data.words, msg->msg_type.rtcm_msgunk, (RTCM_WORDS_MAX-2)*sizeof(isgps30bits_t));
break;
}
}
bool rtcm_repack(struct gps_device_t *session)
/* repack the content fields into the raw bits */
{
int len, sval;
unsigned int n, w, uval;
struct rtcm_t *tp = &session->gpsdata.rtcm;
struct rtcm_msg_t *msg = (struct rtcm_msg_t *)session->driver.isgps.buf;
struct rtcm_msghw1 *wp = (struct rtcm_msghw1 *)session->driver.isgps.buf;
memset(session->driver.isgps.buf, 0, sizeof(session->driver.isgps.buf));
msg->w1.msgtype = tp->type;
msg->w2.frmlen = tp->length;
msg->w2.zcnt = (unsigned) round(tp->zcount / ZCOUNT_SCALE);
msg->w1.refstaid = tp->refstaid;
msg->w2.sqnum = tp->seqnum;
msg->w2.stathlth = tp->stathlth;
len = (int)tp->length;
n = 0;
switch (tp->type) {
case 1: /* S */
case 9:
{
struct b_correction_t *m = &msg->msg_type.type1.corrections[0];
while (len >= 0) {
if (len >= 2) {
struct rangesat_t *ssp = &tp->msg_data.ranges.sat[n];
m->w3.satident1 = ssp->ident;
m->w3.udre1 = ssp->udre;
m->w4.issuedata1 = ssp->issuedata;
m->w3.scale1 = (unsigned)((ssp->rangerr > MAXPCSMALL) ||
(ssp->rangerr < (-MAXPCSMALL)) ||
(ssp->rangerate > MAXRRSMALL) ||
(ssp->rangerate < (-MAXRRSMALL)));
m->w3.pc1 = (int) round(ssp->rangerr / (m->w3.scale1 ? PCLARGE : PCSMALL));
m->w4.rangerate1 = (int) round(ssp->rangerate / (m->w3.scale1 ? RRLARGE : RRSMALL));
n++;
}
if (len >= 4) {
struct rangesat_t *ssp = &tp->msg_data.ranges.sat[n];
m->w4.satident2 = ssp->ident;
m->w4.udre2 = ssp->udre;
m->w6.issuedata2 = ssp->issuedata;
m->w4.scale2 = (unsigned)((ssp->rangerr > MAXPCSMALL) ||
(ssp->rangerr < (-MAXPCSMALL)) ||
(ssp->rangerate > MAXRRSMALL) ||
(ssp->rangerate < (-MAXRRSMALL)));
m->w5.pc2 = (int) round(ssp->rangerr / (m->w4.scale2 ? PCLARGE : PCSMALL));
m->w5.rangerate2 = (int) round(ssp->rangerate / (m->w4.scale2 ? RRLARGE : RRSMALL));
n++;
}
if (len >= 5) {
struct rangesat_t *ssp = &tp->msg_data.ranges.sat[n];
m->w6.satident3 = ssp->ident;
m->w6.udre3 = ssp->udre;
m->w7.issuedata3 = ssp->issuedata;
m->w6.scale3 = (unsigned)((ssp->rangerr > MAXPCSMALL) ||
(ssp->rangerr < (-MAXPCSMALL)) ||
(ssp->rangerate > MAXRRSMALL) ||
(ssp->rangerate < (-MAXRRSMALL)));
sval = (int) round(ssp->rangerr / (m->w6.scale3 ? PCLARGE : PCSMALL));
/*@ -shiftimplementation @*/
m->w6.pc3_h = sval >> 8;
/*@ +shiftimplementation @*/
m->w7.pc3_l = (unsigned)sval & 0xff;
m->w7.rangerate3 = (int) round(ssp->rangerate / (m->w6.scale3 ? RRLARGE : RRSMALL));
n++;
}
len -= 5;
m++;
}
tp->msg_data.ranges.nentries = n;
}
break;
case 3: /* R */
if (tp->msg_data.ecef.valid) {
struct rtcm_msg3 *m = &msg->msg_type.type3;
unsigned x = (unsigned) round(tp->msg_data.ecef.x / XYZ_SCALE);
unsigned y = (unsigned) round(tp->msg_data.ecef.y / XYZ_SCALE);
unsigned z = (unsigned) round(tp->msg_data.ecef.z / XYZ_SCALE);
m->w4.x_l = x & 0xff;
m->w3.x_h = x >> 8;
m->w5.y_l = y & 0xffff;
m->w4.y_h = y >> 16;
m->w6.z_l = z & 0xffffff;
m->w5.z_h = z >> 24;
}
break;
case 4: /* D */
if (tp->msg_data.reference.valid) {
struct rtcm_msg4 *m = &msg->msg_type.type4;
m->w3.dgnss = tp->msg_data.reference.system;
m->w3.dat = (unsigned)(tp->msg_data.reference.sense == global);
/*@ -predboolothers -type @*/
if (tp->msg_data.reference.datum[0])
m->w3.datum_alpha_char1 = tp->msg_data.reference.datum[0];
else
m->w3.datum_alpha_char1 = 0;
if (tp->msg_data.reference.datum[1])
m->w3.datum_alpha_char2 = tp->msg_data.reference.datum[1];
else
m->w3.datum_alpha_char2 = 0;
if (tp->msg_data.reference.datum[2])
m->w4.datum_sub_div_char1 = tp->msg_data.reference.datum[2];
else
m->w4.datum_sub_div_char1 = 0;
if (tp->msg_data.reference.datum[3])
m->w4.datum_sub_div_char2 = tp->msg_data.reference.datum[3];
else
m->w4.datum_sub_div_char2 = 0;
if (tp->msg_data.reference.datum[4])
m->w4.datum_sub_div_char3 = tp->msg_data.reference.datum[4];
else
m->w4.datum_sub_div_char3 = 0;
/*@ +predboolothers +type @*/
if (tp->msg_data.reference.system != unknown) {
m->w5.dx = (uint)round(tp->msg_data.reference.dx / DXYZ_SCALE);
uval = (uint)round(tp->msg_data.reference.dy / DXYZ_SCALE);
m->w5.dy_h = uval >> 8;
m->w6.dy_l = uval & 0xff;
m->w6.dz = (uint)round(tp->msg_data.reference.dz / DXYZ_SCALE);
}
}
break;
case 5: /* C */
for (n = 0; n < (unsigned)len; n++) {
struct consat_t *csp = &tp->msg_data.conhealth.sat[n];
struct b_health_t *m = &msg->msg_type.type5.health[n];
m->sat_id = csp->ident;
m->issue_of_data_link = (unsigned)csp->iodl;
m->data_health = csp->health;
m->cn0 = (csp->snr == SNR_BAD) ? 0 : (unsigned)csp->snr-CNR_OFFSET;
m->health_enable = csp->health_en;
m->new_nav_data = (unsigned)csp->new_data;
m->loss_warn = (unsigned)csp->los_warning;
m->time_unhealthy = (unsigned)(csp->tou / TU_SCALE);
}
break;
case 7: /* A */
for (w = 0; w < (RTCM_WORDS_MAX - 2)/ 3; w++) {
struct station_t *np = &tp->msg_data.almanac.station[n++];
struct b_station_t *mp = &msg->msg_type.type7.almanac[w];
mp->w3.lat = (int) round(np->latitude / LA_SCALE);
sval = (int) round(np->longitude / LO_SCALE);
/*@ -shiftimplementation @*/
mp->w3.lon_h = sval >> 8;
/*@ +shiftimplementation @*/
mp->w4.lon_l = (unsigned)sval & 0xff;
mp->w4.range = np->range;
uval = (unsigned) round(((np->frequency-FREQ_OFFSET) / FREQ_SCALE));
mp->w4.freq_h = uval >> 6;
mp->w5.freq_l = uval & 0x3f;
mp->w5.health = np->health;
mp->w5.station_id = np->station_id;
mp->w5.bit_rate = 0;
for (uval = 0; uval < (unsigned)(sizeof(tx_speed)/sizeof(tx_speed[0])); uval++)
if (tx_speed[uval] == np->bitrate) {
mp->w5.bit_rate = uval;
break;
}
if (mp->w5.bit_rate == 0)
return false;
}
tp->msg_data.almanac.nentries = n;
break;
case 16: /* T */
/*@ -boolops @*/
for (w = 0; w < RTCM_WORDS_MAX - 2; w++){
if (!tp->msg_data.message[n]) {
break;
}
msg->msg_type.type16.txt[w].byte1 = (unsigned)tp->msg_data.message[n++];
if (!tp->msg_data.message[n]) {
break;
}
msg->msg_type.type16.txt[w].byte2 = (unsigned)tp->msg_data.message[n++];
if (!tp->msg_data.message[n]) {
break;
}
msg->msg_type.type16.txt[w].byte3 = (unsigned)tp->msg_data.message[n++];
}
msg->w2.frmlen = w+1;
/*@ +boolops @*/
break;
default: /* U */
memcpy(msg->msg_type.rtcm_msgunk, tp->msg_data.words, (RTCM_WORDS_MAX-2)*sizeof(isgps30bits_t));
break;
}
/* compute parity for each word in the message */
for (w = 0; w < tp->length; w++)
wp[w].parity = isgps_parity(session->driver.isgps.buf[w]);
/* FIXME: must do inversion here */
return true;
}
static bool preamble_match(isgps30bits_t *w)
{
return (((struct rtcm_msghw1 *)w)->preamble == PREAMBLE_PATTERN);
}
static bool length_check(struct gps_device_t *session)
{
return session->driver.isgps.bufindex >= 2
&& session->driver.isgps.bufindex >= ((struct rtcm_msg_t *)session->driver.isgps.buf)->w2.frmlen + 2u;
}
enum isgpsstat_t rtcm_decode(struct gps_device_t *session, unsigned int c)
{
enum isgpsstat_t res = isgps_decode(session,
preamble_match,
length_check,
RTCM_WORDS_MAX,
c);
if (res == ISGPS_MESSAGE)
rtcm_unpack(session);
return res;
}
void rtcm_dump(struct gps_device_t *session, /*@out@*/char buf[], size_t buflen)
/* dump the contents of a parsed RTCM104 message */
{
unsigned int n;
(void)snprintf(buf, buflen, "H\t%u\t%u\t%0.1f\t%u\t%u\t%u\n",
session->gpsdata.rtcm.type,
session->gpsdata.rtcm.refstaid,
session->gpsdata.rtcm.zcount,
session->gpsdata.rtcm.seqnum,
session->gpsdata.rtcm.length,
session->gpsdata.rtcm.stathlth);
switch (session->gpsdata.rtcm.type) {
case 1:
case 9:
for (n = 0; n < session->gpsdata.rtcm.msg_data.ranges.nentries; n++) {
struct rangesat_t *rsp = &session->gpsdata.rtcm.msg_data.ranges.sat[n];
(void)snprintf(buf + strlen(buf), buflen - strlen(buf),
"S\t%u\t%u\t%u\t%0.1f\t%0.3f\t%0.3f\n",
rsp->ident,
rsp->udre,
rsp->issuedata,
session->gpsdata.rtcm.zcount,
rsp->rangerr,
rsp->rangerate);
}
break;
case 3:
if (session->gpsdata.rtcm.msg_data.ecef.valid)
(void)snprintf(buf + strlen(buf), buflen - strlen(buf),
"R\t%.2f\t%.2f\t%.2f\n",
session->gpsdata.rtcm.msg_data.ecef.x,
session->gpsdata.rtcm.msg_data.ecef.y,
session->gpsdata.rtcm.msg_data.ecef.z);
break;
case 4:
if (session->gpsdata.rtcm.msg_data.reference.valid)
(void)snprintf(buf + strlen(buf), buflen - strlen(buf),
"D\t%s\t%1d\t%s\t%.1f\t%.1f\t%.1f\n",
(session->gpsdata.rtcm.msg_data.reference.system==gps) ? "GPS"
: ((session->gpsdata.rtcm.msg_data.reference.system==glonass) ? "GLONASS"
: "UNKNOWN"),
session->gpsdata.rtcm.msg_data.reference.sense,
session->gpsdata.rtcm.msg_data.reference.datum,
session->gpsdata.rtcm.msg_data.reference.dx,
session->gpsdata.rtcm.msg_data.reference.dy,
session->gpsdata.rtcm.msg_data.reference.dz);
break;
case 5:
for (n = 0; n < session->gpsdata.rtcm.msg_data.conhealth.nentries; n++) {
struct consat_t *csp = &session->gpsdata.rtcm.msg_data.conhealth.sat[n];
(void)snprintf(buf + strlen(buf), buflen - strlen(buf),
"C\t%2u\t%1u\t%1u\t%2d\t%1u\t%1u\t%1u\t%2u\n",
csp->ident,
(unsigned)csp->iodl,
(unsigned)csp->health,
csp->snr,
(unsigned)csp->health_en,
(unsigned)csp->new_data,
(unsigned)csp->los_warning,
csp->tou);
}
break;
case 6: /* NOP msg */
strcat(buf, "N\n");
break;
case 7:
for (n = 0; n < session->gpsdata.rtcm.msg_data.almanac.nentries; n++) {
struct station_t *ssp = &session->gpsdata.rtcm.msg_data.almanac.station[n];
(void)snprintf(buf + strlen(buf), buflen - strlen(buf),
"A\t%.4f\t%.4f\t%u\t%.1f\t%u\t%u\t%u\n",
ssp->latitude,
ssp->longitude,
ssp->range,
ssp->frequency,
ssp->health,
ssp->station_id,
ssp->bitrate);
}
break;
case 16:
(void)snprintf(buf + strlen(buf), buflen - strlen(buf),
"T\t\"%s\"\n", session->gpsdata.rtcm.msg_data.message);
break;
default:
for (n = 0; n < session->gpsdata.rtcm.length; n++)
(void)snprintf(buf + strlen(buf), buflen - strlen(buf),
"U\t0x%08x\n", session->gpsdata.rtcm.msg_data.words[n]);
break;
}
}
int rtcm_undump(/*@out@*/struct rtcm_t *rtcmp, char *buf)
/* merge a line of data into an RTCM structure, return 0 if done */
{
int fldcount, v;
unsigned n;
char buf2[BUFSIZ];
/*@ -usedef @*/
switch (rtcmp->type) {
case 0:
fldcount = sscanf(buf, "H\t%u\t%u\t%lf\t%u\t%u\t%u\n",
&rtcmp->type,
&rtcmp->refstaid,
&rtcmp->zcount,
&rtcmp->seqnum,
&rtcmp->length,
&rtcmp->stathlth);
if (fldcount != 6)
return -1;
else
return 1;
//break;
case 1:
case 9:
{
struct rangesat_t *rsp = &rtcmp->msg_data.ranges.sat[rtcmp->msg_data.ranges.nentries++];
/* we ignore the third (zcount) field, it's in the parent */
fldcount = sscanf(buf,
"S\t%u\t%u\t%u\t%*f\t%lf\t%lf\n",
&rsp->ident,
&rsp->udre,
&rsp->issuedata,
&rsp->rangerr,
&rsp->rangerate);
if (fldcount != 5 || (rtcmp->type != 1 && rtcmp->type != 9))
return (int)(-rtcmp->type-1);
else if (rtcmp->msg_data.ranges.nentries != rtcmp->length*3/5)
return (int)(rtcmp->type+1);
else
return 0;
}
//break;
case 3:
fldcount = sscanf(buf,
"R\t%lf\t%lf\t%lf\n",
&rtcmp->msg_data.ecef.x,
&rtcmp->msg_data.ecef.y,
&rtcmp->msg_data.ecef.z);
if (fldcount != 3 || rtcmp->type != 3)
return -4;
else {
rtcmp->msg_data.ecef.valid = true;
return 0;
}
//break;
case 4:
fldcount = sscanf(buf,
"D\t%s\t%1d\t%s\t%lf\t%lf\t%lf\n",
buf2,
&v,
(char *)&rtcmp->msg_data.reference.datum,
&rtcmp->msg_data.reference.dx,
&rtcmp->msg_data.reference.dy,
&rtcmp->msg_data.reference.dz);
if (fldcount != 6 || rtcmp->type != 4)
return -5;
else {
if (strcmp(buf2, "GPS") == 0)
rtcmp->msg_data.reference.system = gps;
else if (strcmp(buf2, "GLONASS") == 0)
rtcmp->msg_data.reference.system = glonass;
else
rtcmp->msg_data.reference.system = unknown;
rtcmp->msg_data.reference.sense = (v == 1) ? global : ((v == 0) ? local : invalid);
rtcmp->msg_data.reference.valid = true;
return 0;
}
//break;
case 5:
{
struct consat_t *csp = &rtcmp->msg_data.conhealth.sat[rtcmp->msg_data.conhealth.nentries++];
fldcount = sscanf(buf,
"C\t%2u\t%1u\t%1u\t%2d\t%1u\t%1u\t%1u\t%2u\n",
&csp->ident,
(unsigned int *)&csp->iodl,
&csp->health,
&csp->snr,
&csp->health_en,
(unsigned int *)&csp->new_data,
(unsigned int *)&csp->los_warning,
&csp->tou);
if (fldcount != 8 || rtcmp->type != 5)
return -6;
else if (rtcmp->msg_data.conhealth.nentries < rtcmp->length)
return 6;
else
return 0;
}
//break;
case 6: /* NOP msg */
if (buf[0] != 'N')
return -7;
else
return 0;
//break;
case 7:
{
struct station_t *ssp = &rtcmp->msg_data.almanac.station[rtcmp->msg_data.almanac.nentries++];
fldcount = sscanf(buf,
"A\t%lf\t%lf\t%u\t%lf\t%u\t%u\t%u\n",
&ssp->latitude,
&ssp->longitude,
&ssp->range,
&ssp->frequency,
&ssp->health,
&ssp->station_id,
&ssp->bitrate);
if (fldcount != 7 || rtcmp->type != 7)
return 8;
else if (rtcmp->msg_data.almanac.nentries < rtcmp->length/3)
return 8;
else
return 0;
}
//break;
case 16:
fldcount = sscanf(buf, "T\t\"%[^\"]\"\n", rtcmp->msg_data.message);
if (fldcount != 1)
return 16;
else
return 0;
//break;
default:
for (n = 0; n < (unsigned)(sizeof(rtcmp->msg_data.words)/sizeof(rtcmp->msg_data.words[0])); n++)
if (rtcmp->msg_data.words[n] == 0)
break;
fldcount = sscanf(buf, "U\t0x%08x\n", &v);
if (fldcount != 1)
return (int)(-rtcmp->type-1);
else {
rtcmp->msg_data.words[n] = (isgps30bits_t)v;
if (n == rtcmp->length-1)
return 0;
else
return (int)(rtcmp->type+1);
}
//break;
}
/*@ +usedef @*/
}
#ifdef __UNUSED__
/*
* The RTCM words are 30-bit words. We will lay them into memory into
* 30-bit (low-end justified) chunks. To write them out we will write
* 5 Magnavox-format bytes where the low 6-bits of the byte are 6-bits
* of the 30-word msg.
*/
void rtcm_output_mag(isgps30bits_t * ip)
/* ship an RTCM message to standard output in Magnavox format */
{
static isgps30bits_t w = 0;
int len;
static uint sqnum = 0;
len = ((struct rtcm_msg *) ip)->w2.frmlen + 2;
((struct rtcm_msg *) ip)->w2.sqnum = sqnum++;
sqnum &= 0x7;
while (len-- > 0) {
w <<= 30;
w |= *ip++ & W_DATA_MASK;
w |= rtcmparity(w);
/* weird-assed inversion */
if (w & P_30_MASK)
w ^= W_DATA_MASK;
/* msb first */
putchar(MAG_TAG_DATA | reverse_bits[(w >> 24) & 0x3f]);
putchar(MAG_TAG_DATA | reverse_bits[(w >> 18) & 0x3f]);
putchar(MAG_TAG_DATA | reverse_bits[(w >> 12) & 0x3f]);
putchar(MAG_TAG_DATA | reverse_bits[(w >> 6) & 0x3f]);
putchar(MAG_TAG_DATA | reverse_bits[(w) & 0x3f]);
}
}
#endif /* UNUSED */
#endif /* RTCM104_ENABLE */
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