Set the GPS device in raw mode and no delay, to cope with different G…

…PS receivers behavior

Makefile

@@ -1,5 +1,5 @@
 
-OBJS= hc_db.o hc_http.o hc_clock.o hc_nmea.o hc_broadcast.o hc_ntp.o houseclock.o
+OBJS= hc_db.o hc_http.o hc_clock.o hc_tty.o hc_nmea.o hc_broadcast.o hc_ntp.o houseclock.o
 
 all: houseclock
 

hc_nmea.c

@@ -69,8 +69,10 @@
  *      -gps=<dev>      Name of the system device to read the NMEA data from.
  *      -latency=<N>    Delay between the GPS fix and the 1st sentence (ms).
  *      -burst          Use burst start as the GPS fix timing reference.
+ *      -baud=<N>       GPS line baud speed.
  *
- *    The default GPS device is /dev/ttyACM0.
+ *    The default GPS device is /dev/ttyACM0. If no baud option is used,
+ *    the default OS configuration is used.
  *
  *    The latency depends on the GPS device. It can be estimated by using
  *    the options -drift and -latency=0, and then estimating the average
@@ -122,11 +124,11 @@
 #include <sys/stat.h>
 #include <fcntl.h>
 #include <time.h>
-#include <termios.h>
 
 #include "houseclock.h"
 #include "hc_db.h"
 #include "hc_clock.h"
+#include "hc_tty.h"
 #include "hc_nmea.h"
 
 static int gpsLatency;
@@ -149,6 +151,7 @@ static int gpsTty = -1;
 static int gpsUseBurst = 0;
 static int gpsPrivacy = 0;
 static int gpsShowNmea = 0;
+static int gpsSpeed = 0;
 
 static time_t gpsInitialized = 0;
 
@@ -157,9 +160,10 @@ static hc_nmea_status *hc_nmea_status_db = 0;
 const char *hc_nmea_help (int level) {
 
     static const char *nmeaHelp[] = {
-        " [-gps=DEV] [-latency=N] [-burst] [-privacy]",
+        " [-gps=DEV] [-baud=N] [-latency=N] [-burst] [-privacy]",
         "-gps=DEV:     device from which to read the NMEA data (/dev/ttyACM0).",
         "-latency=N:   delay between the GPS fix and the 1st NMEA sentence (70).",
+        "-baud=N:      GPS device's baud speed (default: use OS default).",
         "-show-nmea:   trace NMEA sentences.",
         "-burst:       Use burst start as the GPS timing reference",
         "-privacy:     do not export location",
@@ -189,18 +193,21 @@ int hc_nmea_initialize (int argc, const char **argv) {
 
     int i;
     const char *latency_option = "70";
+    const char *speed_option = "0";
 
     gpsDevice = "/dev/ttyACM0";
     gpsUseBurst = 0;
 
     for (i = 1; i < argc; ++i) {
         hc_match ("-gps=", argv[i], &gpsDevice);
+        hc_match ("-baud=", argv[i], &speed_option);
         hc_match ("-latency=", argv[i], &latency_option);
         if (hc_present ("-burst", argv[i])) gpsUseBurst = 1;
         if (hc_present ("-privacy", argv[i])) gpsPrivacy = 1;
         if (hc_present ("-show-nmea", argv[i])) gpsShowNmea = 1;
     }
     gpsLatency = atoi(latency_option);
+    gpsSpeed = atoi(speed_option);
 
     if (hc_nmea_status_db == 0) {
         i = hc_db_new (HC_NMEA_STATUS, sizeof(hc_nmea_status), 1);
@@ -217,12 +224,7 @@ int hc_nmea_initialize (int argc, const char **argv) {
 
     // Remove echo of characters from the GPS device.
     if (gpsTty >= 0) {
-        struct termios options;
-        int status = tcgetattr(gpsTty, &options);
-        if (status == 0) {
-            options.c_lflag &= (~(ECHO+ECHONL));
-            tcsetattr(gpsTty, TCSANOW, &options);
-        }
+        hc_tty_set (gpsTty, gpsSpeed);
     }
 
     gpsInitialized = time(0);

hc_tty.c

@@ -0,0 +1,112 @@
+/* houseclock - A simple GPS Time Server with Web console
+ *
+ * Copyright 2019, Pascal Martin
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA  02110-1301, USA.
+ *
+ *
+ * hc_tty.c - Handle setting up a TTY device.
+ *
+ * This module hides the TTY configuration's OS interface.
+ */
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/termios.h>
+
+#include "hc_tty.h"
+
+int hc_tty_set (int fd, int baud) {
+
+    int speed;
+    struct termios settings;
+
+    if (! isatty(fd)) return 0; // No need to setup anything.
+
+    if (tcgetattr(fd,&settings) != 0) return errno;
+
+    // Optionally set the speed (if not 0). This is mostly useless with
+    // current USB GPS devices, but let's still allow it for special cases.
+
+    switch(baud) {
+        case      0: speed =      B0; break;
+        case     50: speed =     B50; break;
+        case     75: speed =     B75; break;
+        case    110: speed =    B110; break;
+        case    134: speed =    B134; break;
+        case    150: speed =    B150; break;
+        case    200: speed =    B200; break;
+        case    300: speed =    B300; break;
+        case    600: speed =    B600; break;
+        case   1200: speed =   B1200; break;
+        case   1800: speed =   B1800; break;
+        case   2400: speed =   B2400; break;
+        case   4800: speed =   B4800; break;
+        case   9600: speed =   B9600; break;
+        case  19200: speed =  B19200; break;
+        case  38400: speed =  B38400; break;
+        case  57600: speed =  B57600; break;
+        case 115200: speed = B115200; break;
+#ifdef B230400
+        case 230400: speed = B230400; break;
+#endif
+#ifdef B460800
+        case 460800: speed = B460800; break;
+#endif
+#ifdef B921600
+        case 921600: speed = B921600; break;
+#endif
+        default: speed = B4800; break;
+    }
+
+    if (speed != B0) {
+        cfsetispeed(&settings, speed);
+        cfsetospeed(&settings, speed);
+    }
+
+    // Set the TTY as raw & non-blocking, 8 bits no parity, 1 stop bit,
+    // and VMIN = 0 and VTIME = 0 (return NMEA data as soon as received,
+    // so that the timing calculations means something).
+
+    memset(settings.c_cc, 0, sizeof(settings.c_cc));
+
+    settings.c_iflag = settings.c_oflag = settings.c_lflag = 0;
+
+    settings.c_cflag &= ~(CSTOPB | PARENB | PARODD | CRTSCTS | CSIZE);
+    settings.c_cflag |= (CREAD | CLOCAL | CS8);
+
+    if (tcsetattr(fd, TCSANOW, &settings) != 0) return errno;
+    if (fcntl(fd, F_SETFL, fcntl(fd, F_GETFL) & !O_NONBLOCK) != 0) return errno;
+
+    tcflush(fd, TCIOFLUSH);
+    return 0;
+}
+
+#ifdef TTY_TEST
+int main (int argc, char **argv) {
+
+    hc_tty_set (open (argv[1], O_RDWR|O_NONBLOCK|O_NOCTTY), 4800);
+
+    // Just wait until killed.
+    for (;;) sleep(1);
+}
+#endif
+

hc_tty.h

@@ -0,0 +1,24 @@
+/* houseclock - A simple GPS Time Server with Web console
+ *
+ * Copyright 2019, Pascal Martin
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA  02110-1301, USA.
+ *
+ *
+ * hc_tty.h - tty configuration's OS interface.
+ */
+int hc_tty_set (int fd, int baud);
+