Add Sirf mode input to NMEA realtime position reader.

diff --git a/nmea.c b/nmea.c
index 152c6c3eb327c8ea00dd2f3f20e6e49732fe2f89..8f9cc42d6777f10fd7723cc1378224b540dd199b 100644 (file)
--- a/nmea.c
+++ b/nmea.c
@@ -830,6 +830,8 @@ nmea_rd_posn_init(const char *fname)
                fatal(MYNAME ": Could not open '%s' for position tracking.\n", fname);
        }
 
+       gbser_flush(gbser_handle);
+
        if (opt_baud) {
                if (!gbser_set_speed(gbser_handle, atoi(opt_baud))) {
                        fatal(MYNAME ": Unable to set baud rate %s\n", opt_baud);
@@ -837,6 +839,57 @@ nmea_rd_posn_init(const char *fname)
        }
        posn_fname = fname;
 }
+static 
+safe_print(int cnt, const char *b)  
+{
+       int i;
+       for (i = 0; i < cnt; i++) {
+               char c = isprint(b[i]) ? b[i] : '.';
+               fputc(c, stderr);
+       }
+}
+
+static 
+int hunt_sirf(void)
+{
+       /* Try to place the common BR's first to speed searching */
+       static int br[] = {38400, 9600, 57600, 115200, 19200, 4800, -1};
+       static int *brp = &br[0];
+       char ibuf[1024];
+
+       for (brp = br; *brp > 0; brp++) {
+               int rv;
+               if (global_opts.debug_level > 1) {
+                       fprintf(stderr, "Trying %d\n", *brp);
+               }
+
+               /* 
+                * Cycle our port's data speed and spray the "change to NMEA
+                * mode to the device.
+                */
+               gbser_set_speed(gbser_handle, *brp);
+               reset_sirf_to_nmea(*brp);
+
+               rv = gbser_read_line(gbser_handle, ibuf, sizeof(ibuf), 
+                       1000, 0x0a, 0x0d);
+               /* 
+                * If we didn't get a read error but did get a string that
+                * started with a dollar sign, we're probably in NMEA mode 
+                * now.
+                */
+               if ((rv > -1) && (strlen(ibuf) > 0) && ibuf[0] == '$') {
+                       return 1;
+               }
+
+               /*
+                * If nothing was received, it's not a sirf part.  Fast exit.
+                */
+               if (rv < 0) {
+                       return 0;
+               }
+       }
+       return 0;
+}
 
 static waypoint *
 nmea_rd_posn(posn_status *posn_status)
@@ -844,6 +897,7 @@ nmea_rd_posn(posn_status *posn_status)
        char ibuf[1024];
        static double lt = -1;
        int i;
+       int am_sirf = 0;
 
        /*
         * Read a handful of sentences, collecting the best info we
@@ -851,14 +905,29 @@ nmea_rd_posn(posn_status *posn_status)
         * about to restart and thus the one we're collecting isn't going
         * to get any better than we now have) hand that back to the caller.
         */
+       
        for (i = 0; i < 10; i++) {
                int rv;
                ibuf[0] = 0;
                rv = gbser_read_line(gbser_handle, ibuf, sizeof(ibuf), 2000, 0x0a, 0x0d);
                if (global_opts.debug_level > 1) {
-                       warning( "READ: %s\n", ibuf);
+                       safe_print(strlen(ibuf), ibuf);
                }
                if (rv < 0) {
+                       if (am_sirf == 0) {
+                               if (global_opts.debug_level > 1) {
+                                       warning(MYNAME ": Attempting sirf mode.\n");
+                               }
+                               /* This is tacky, we have to change speed
+                                * to 9600bps to tell it to speak NMEA at
+                                * 4800.
+                                */
+                               am_sirf = hunt_sirf();
+                               if (am_sirf) {
+                                       i = 0;
+                                       continue;
+                               }
+                       }
                        fatal(MYNAME ": No data received on %s.\n", posn_fname);
                }
                nmea_parse_one_line(ibuf);
@@ -1049,3 +1118,54 @@ ff_vecs_t nmea_vecs = {
        CET_CHARSET_ASCII, 0,   /* CET-REVIEW */
        { nmea_rd_posn_init, nmea_rd_posn, nmea_rd_deinit, NULL, NULL, NULL }
 };
+
+/*
+ * If we later decide to implement a "real" Sirf module, this code should
+ * go there.  For now, we try a kind of heavy handed thing - if we don't
+ * see NMEA-isms from the device, we'll go on the premise that it MAY be
+ * a SiRF Star device and send it the "speak NMEA, please" command.
+ */
+
+static void
+sirf_write(unsigned char *buf)
+{
+       int i, chksum = 0;
+       int len = buf[2] << 8 | buf[3];
+
+       for (i = 0; i < len; i++) {
+               chksum += buf[4 + i];
+       }
+       chksum &= 0x7fff;
+
+       buf[len + 4] = chksum  >> 8;
+       buf[len + 5] = chksum  & 0xff;
+
+       gbser_write(gbser_handle, buf, len + 8);  /* 4 at front, 4 at back */
+}
+
+static
+void reset_sirf_to_nmea(int br)
+{
+       static unsigned char pkt[] = {0xa0, 0xa2, 0x00, 0x18,
+               0x81, 0x02,
+               0x01, 0x01, /* GGA */
+               0x00, 0x00, /* suppress GLL */
+               0x01, 0x00, /* suppress GSA */
+               0x05, 0x00, /* suppress GSV */
+               0x01, 0x01, /* use RMC for date*/
+               0x00, 0x00, /* suppress VTG */
+               0x00, 0x01, /* output rate */
+               0x00, 0x01, /* unused recommended values */
+               0x00, 0x01, 
+               0x00, 0x01, /* ZDA */
+               0x12, 0xc0, /* 4800 bps */
+               0x00, 0x00,  /* checksum */
+               0xb0, 0xb3}; /* packet end */
+       /* repopulate bit rate */
+       pkt[26] = br >> 8;
+       pkt[27] = br & 0xff;
+
+       sirf_write(pkt);
+       gb_sleep(250 * 1000);
+       gbser_flush(gbser_handle);
+}

diff --git a/xmldoc/formats/nmea.xml b/xmldoc/formats/nmea.xml
index 6fdc4d4ee49f83659b72e8bfacab6738b0d2116c..a7fe63ed425a274033a6710b14558d252c12c80b 100644 (file)
--- a/xmldoc/formats/nmea.xml
+++ b/xmldoc/formats/nmea.xml
@@ -40,3 +40,11 @@ which allows realtime position reports from a GPS, such as one connected
 serially, over Bluetooth, or a USB module emulating a serial port, to be used
 with selected output formats.
 </para>
+<para>
+When used in <link linkend="tracking">realtime tracking</link> mode, if
+GPSBabel does not sense incoming NMEA sentences arriving from the port, it
+will send Sirf "reset to NMEA" commands to the port at a variety of speeds
+in an attempt to communicate with an attached GPS.   This lets devices
+like the Microsoft GPS or Pharos GPS that are Sirf chips with an integrated
+USB/Serial adapter work with this input format.
+</para>