Autodetect and configure Spectratime iSync device

The Spectratime iSync devices comprise a u-blox 6 attached to a
separate iSync microcontroller which drives a rubidium oscillator.
The oscillator status messages may appear in the middle of the
underlying GPS messages; these are handled via the "stashed partial
message" support.

This patch modifies the u-blox driver's parse_input() method to
delegate NMEA messages to generic_parse_input() rather than
nmea_parse().  This is done to allow the iSync trigger string to be
detected after reactivation despite the "stickiness" of the u-blox
driver.

The initial delay time in gpsfake is extended from 1.0 seconds to 1.4
seconds to allow for the additional two 200ms delays introduced by the
calls to gpsd_set_speed() in isync_detect().

The iSync driver legitimately uses both a probe_detect() method and a
trigger string.  The guard against such drivers is therefore removed
from test_packet.c.

The regression test data includes one artificially induced packet
collision (where an oscillator status message appears in the middle of
a GPS message), since this corner case is difficult to trigger
deliberately in normal operation.

Signed-off-by: Michael Brown <mbrown@fensystems.co.uk>

1 files changed, 170 insertions, 0 deletions

diff --git a/drivers.c b/drivers.c
index 0ce47e8d..5d62706b 100644
--- a/drivers.c
+++ b/drivers.c
@@ -1152,6 +1152,173 @@ const struct gps_type_t driver_mtk3301 = {
 /* *INDENT-ON* */
 #endif /* MTK3301_ENABLE */
 
+#ifdef ISYNC_ENABLE
+/**************************************************************************
+ *
+ * Spectratime LNRCLOK / GRCLOK iSync GPS-disciplined rubidium oscillators
+ *
+ * These devices comprise a u-blox 6 attached to a separate iSync
+ * microcontroller which drives the rubidium oscillator.  The iSync
+ * microcontroller can be configured to pass through the underlying
+ * GPS communication channel, while still using the GPS PPSREF signal
+ * to discipline the rubidium oscillator.
+ *
+ * The iSync can also generate its own periodic status packets in NMEA
+ * format.  These describe the state of the oscillator (including
+ * whether or not the oscillator PPSOUT is synced to the GPS PPSREF).
+ * These packets are transmitted in the middle of the underlying GPS
+ * packets, forcing us to handle interrupted NMEA packets.
+ *
+ * The default state of the device is to generate no periodic output.
+ * We send a probe string to initiate beating of the iSync-proprietary
+ * $PTNTS,B message, which is then detected as a NMEA trigger.
+ *
+ **************************************************************************/
+
+static ssize_t isync_write(struct gps_device_t *session, const char *data)
+
+{
+    return gpsd_write(session, data, strlen(data));
+}
+
+static bool isync_detect(struct gps_device_t *session)
+{
+    speed_t old_baudrate;
+    char old_parity;
+    unsigned int old_stopbits;
+
+    /* Set 9600 8N1 */
+    old_baudrate = session->gpsdata.dev.baudrate;
+    old_parity = session->gpsdata.dev.parity;
+    old_stopbits = session->gpsdata.dev.stopbits;
+    gpsd_set_speed(session, 9600, 'N', 1);
+
+    /* Cancel pass-through mode and initiate beating of $PTNTS,B
+     * message, which can subsequently be detected as a trigger.
+     */
+    (void)isync_write(session, "@@@@\r\nMAW0C0B\r\n");
+
+    /* return serial port to original settings */
+    gpsd_set_speed(session, old_baudrate, old_parity, old_stopbits);
+
+    return false;
+}
+
+static void isync_event_hook(struct gps_device_t *session, event_t event)
+{
+    if (session->context->readonly)
+	return;
+
+    if (event == event_driver_switch) {
+	session->lexer.counter = 0;
+    }
+
+    if (event == event_configure) {
+	switch (session->lexer.counter) {
+	case 1:
+	    /* Configure timing and frequency flags:
+	     *  - Thermal compensation active
+	     *  - PPSREF active
+	     *  - PPSOUT active
+	     */
+	    (void)isync_write(session, "MAW040B\r\n");
+	    /* Configure tracking flags:
+	     *  - Save frequency every 24 hours
+	     *  - Align PPSOUT to PPSINT
+	     *  - Track PPSREF
+	     */
+	    (void)isync_write(session, "MAW0513\r\n");
+	    /* Configure tracking start flags:
+	     *  - Tracking restart allowed
+	     *  - Align to PPSREF
+	     */
+	    (void)isync_write(session, "MAW0606\r\n");
+	    /* Configure tracking window:
+	     *  - 4us
+	     */
+	    (void)isync_write(session, "MAW1304\r\n");
+	    /* Configure alarm window:
+	     *  - 4us
+	     */
+	    (void)isync_write(session, "MAW1404\r\n");
+	    break;
+	case 2:
+	    /* Configure pulse every d second:
+	     *  - pulse every second
+	     */
+	    (void)isync_write(session, "MAW1701\r\n");
+	    /* Configure pulse origin:
+	     *  - zero offset
+	     */
+	    (void)isync_write(session, "MAW1800\r\n");
+	    /* Configure pulse width:
+	     *  - 600ms
+	     */
+	    (void)isync_write(session, "MAW1223C34600\r\n");
+	    break;
+	case 3:
+	    /* Configure GPS resource utilization:
+	     *  - do not consider GPS messages
+	     */
+	    (void)isync_write(session, "MAW2200\r\n");
+	    /* Restart sync */
+	    (void)isync_write(session, "SY1\r\n");
+	    /* Restart tracking */
+	    (void)isync_write(session, "TR1\r\n");
+	    break;
+	case 4:
+	    /* Cancel BTx messages (if any) */
+	    (void)isync_write(session, "BT0\r\n");
+	    /* Configure messages coming out every second:
+	     *  - Oscillator status ($PTNTA) at 750ms
+	     */
+	    (void)isync_write(session, "MAW0B00\r\n");
+	    (void)isync_write(session, "MAW0C0A\r\n");
+	    break;
+	case 5:
+	    /* Enable GPS passthrough and force u-blox driver to
+	     * select NMEA mode.
+	     */
+	    session->mode = 0;
+	    session->drivers_identified = 0;
+	    (void)isync_write(session, "@@@@GPS\r\n");
+	    break;
+	case 6:
+	    /* Trigger detection of underlying u-blox (if necessary) */
+	    (void)ubx_write(session, 0x06, 0x00, NULL, 0);
+	    break;
+	}
+    }
+}
+
+/* *INDENT-OFF* */
+const struct gps_type_t driver_isync = {
+    .type_name      = "iSync",		/* full name of type */
+    .packet_type    = NMEA_PACKET,	/* associated lexer packet type */
+    .flags          = DRIVER_STICKY,	/* remember this */
+    .trigger	    = "$PTNTS,B,",	/* iSync status message */
+    .channels       = 50,		/* copied from driver_ubx */
+    .probe_detect   = isync_detect,	/* how to detect at startup time */
+    .get_packet     = generic_get,	/* how to get a packet */
+    .parse_packet   = generic_parse_input,	/* how to interpret a packet */
+    .init_query     = NULL,		/* non-perturbing initial query */
+    .event_hook     = isync_event_hook,	/* lifetime event handler */
+#ifdef RECONFIGURE_ENABLE
+    .speed_switcher = NULL,		/* no speed switcher */
+    .mode_switcher  = NULL,		/* no mode switcher */
+    .rate_switcher  = NULL,		/* no sample-rate switcher */
+    .min_cycle      = 1,		/* not relevant, no rate switch */
+#endif /* RECONFIGURE_ENABLE */
+#ifdef CONTROLSEND_ENABLE
+    .control_send   = nmea_write,	/* how to send control strings */
+#endif /* CONTROLSEND_ENABLE */
+#ifdef TIMEHINT_ENABLE
+    .time_offset     = NULL,		/* no method for NTP fudge factor */
+#endif /* TIMEHINT_ENABLE */
+};
+/* *INDENT-ON* */
+#endif /* ISYNC_ENABLE */
+
 #ifdef AIVDM_ENABLE
 /**************************************************************************
  *
@@ -1626,6 +1793,9 @@ static const struct gps_type_t *gpsd_driver_array[] = {
 #ifdef TSIP_ENABLE
     &driver_tsip,
 #endif /* TSIP_ENABLE */
+#ifdef ISYNC_ENABLE
+    &driver_isync,
+#endif /* ISYNC_ENABLE */
 #ifdef UBLOX_ENABLE
     &driver_ubx,
 #endif /* UBLOX_ENABLE */