gps: modem GNSS -> gpsd -> OwnTracks/MQTT publisher

EC25-AF GNSS wiring (udev hotplug into gpsd) plus van-gps-owntracks, a
port of the wayback-era gps_to_owntracks.py: apt-only deps (python3-gps
instead of pip-only gpsdclient, paho 2.x callback API), broker secrets
moved out of the code into /etc/van-gps/config.json (0600, seeded from
a sanitized example), gpsd host now localhost. client_id is vanq-wan —
a legacy client still holds vanq on the broker and shared IDs get
kicked in a connect/disconnect loop. Exit-on-disconnect + systemd
Restart=always is the reconnect logic.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

gps/van-gps-owntracks

@@ -0,0 +1,161 @@
+#!/usr/bin/python3 -u
+# Publish gpsd fixes as OwnTracks location messages over MQTT.
+# Ported from gps_to_owntracks.py (wayback era): gpsdclient -> python3-gps
+# (apt-only deps), paho 1.x -> 2.x callback API, hard-coded broker secrets ->
+# /etc/van-gps/config.json. Exits on MQTT disconnect/DNS failure by design —
+# systemd Restart=always reconnects with a fresh session.
+
+import sys
+import json
+import signal
+import os
+import time
+import socket
+
+import gps as gpsd
+import paho.mqtt.client as mqtt
+from paho.mqtt.properties import Properties
+from paho.mqtt.packettypes import PacketTypes
+
+from datetime import datetime
+from math import radians, sin, cos, acos
+
+debug = False           # toggle at runtime with SIGHUP
+config_path = sys.argv[1] if len(sys.argv) > 1 else "/etc/van-gps/config.json"
+with open(config_path) as f:
+    cfg = json.load(f)
+
+version = cfg.get("mqtt_version", "3")          # '3' or '5'
+mytransport = "tcp"                             # or 'websockets'
+broker = cfg["broker"]
+myport = cfg.get("port", 1883)
+mq_user = cfg["username"]
+mq_pw = cfg["password"]
+mq_id = cfg.get("client_id", "vanq-wan")
+gpsd_host = cfg.get("gpsd_host", "127.0.0.1")
+idle_delay = cfg.get("idle_delay_s", 600)       # seconds between messages when not moving
+keep_alive = idle_delay + 60
+distance_move_trigger = cfg.get("move_trigger_m", 250)  # meters of movement that triggers a message
+
+mytopic = cfg.get("topic", "owntracks/rv/gps")
+tid = cfg.get("tid", "rv")
+
+
+def handler(signum, frame):
+    global debug
+    debug = not debug
+    print('debug is now', debug)
+
+
+def great_circle(llon1, llat1, llon2, llat2):
+    lon1, lat1, lon2, lat2 = map(radians, [llon1, llat1, llon2, llat2])
+
+    a = sin(lat1) * sin(lat2) + cos(lat1) * cos(lat2) * cos(lon1 - lon2)
+    if a >= 1.0:
+        return 0
+    try:
+        res = int(6371000 * (acos(a)))
+    except ValueError as e:
+        print("gc error: ", e)
+        print(" coords: ", llon1, llat1, llon2, llat2)
+        return 0
+    return res
+
+
+def on_disconnect(client, userdata, flags, reason_code, properties):
+    print("mqtt disconnect:", reason_code)
+    os._exit(1)
+
+
+def connect():
+    if version == '5':
+        properties = Properties(PacketTypes.CONNECT)
+        properties.SessionExpiryInterval = 30 * 60  # in seconds
+
+        client.connect(broker,
+                       port=myport,
+                       clean_start=mqtt.MQTT_CLEAN_START_FIRST_ONLY,
+                       properties=properties,
+                       keepalive=keep_alive)
+    elif version == '3':
+        client.connect(broker, port=myport, keepalive=keep_alive)
+    print("mqtt connect")
+
+
+#
+# Main
+#
+
+print("van-gps-owntracks start", time.asctime(), debug, os.getpid())
+
+signal.signal(signal.SIGHUP, handler)
+
+if version == '5':
+    client = mqtt.Client(mqtt.CallbackAPIVersion.VERSION2,
+                         client_id=mq_id,
+                         transport=mytransport,
+                         protocol=mqtt.MQTTv5)
+if version == '3':
+    client = mqtt.Client(mqtt.CallbackAPIVersion.VERSION2,
+                         client_id=mq_id,
+                         transport=mytransport,
+                         protocol=mqtt.MQTTv311,
+                         clean_session=True)
+
+client.username_pw_set(mq_user, mq_pw)
+client.on_disconnect = on_disconnect
+
+try:
+    connect()
+except socket.gaierror as e:
+    print("could not connect mqtt, %s" % e)
+    sys.exit(1)
+client.loop_start()
+
+pubproperties = Properties(PacketTypes.PUBLISH)
+pubproperties.MessageExpiryInterval = keep_alive  # in seconds; MQTT5 only
+
+session = gpsd.gps(host=gpsd_host)
+session.stream(gpsd.WATCH_ENABLE)
+lastmsg = {'tst': 0, 'tid': tid, 'lat': 0, 'lon': 0}
+while session.read() == 0:
+    result = session.data
+    if not result or result.get('class') != 'TPV':
+        continue
+    msg = {'_type': 'location', 'tid': tid, 't': 'p'}
+
+    if result.get('mode', 0) <= 1:
+        continue
+    if not ('lat' in result and 'lon' in result):
+        continue
+    msg['lat'] = result['lat']
+    msg['lon'] = result['lon']
+    if 'alt' in result:
+        msg['alt'] = int(result['alt'])
+    if 'speed' in result:
+        msg['vel'] = int(result['speed']) * 3.6
+    if 'eph' in result:
+        msg['acc'] = int(result['eph'])
+    if 'track' in result:
+        msg['cog'] = int(result['track'])
+    else:
+        continue
+    if 'time' not in result:
+        continue
+    msg['tst'] = int(datetime.fromisoformat(result['time']).timestamp())
+    jmsg = json.dumps(msg)
+    if lastmsg != msg:
+        gc = great_circle(lastmsg['lat'], lastmsg['lon'], msg['lat'], msg['lon'])
+        if debug:
+            print("\rgc is ", gc, ' age is ', msg['tst'] - lastmsg['tst'], "   ", end="")
+        if msg['tst'] - lastmsg['tst'] >= idle_delay or gc > distance_move_trigger:
+            if debug:
+                print('* ', gc, jmsg)
+                print('* ', mytopic, pubproperties)
+            rc = client.publish(mytopic, jmsg, 0, properties=pubproperties)
+            if debug:
+                print("*  client.publish rc=", rc)
+            lastmsg = msg
+
+print("gpsd stream ended", file=sys.stderr)
+sys.exit(1)