Allow hot reconnection from another gcs over wifi

Switch back to udp broadcasting if no messages from gcs for 5 seconds

flix/mavlink.ino

@@ -17,7 +17,7 @@ Rate telemetryRC(10);
 Rate telemetryMotors(10);
 Rate telemetryIMU(15);
 
-bool mavlinkConnected = false;
+float mavlinkTime = NAN; // time of last received message
 String mavlinkPrintBuffer;
 
 void processMavlink() {
@@ -40,7 +40,7 @@ void sendMavlink() {
 		sendMessage(&msg);
 	}
 
-	if (!mavlinkConnected) return; // send only heartbeat until connected
+	if (!valid(mavlinkTime)) return; // send only heartbeat until connected
 
 	if (telemetrySlow) {
 		mavlink_msg_extended_sys_state_pack(mavlinkSysId, MAV_COMP_ID_AUTOPILOT1, &msg,
@@ -101,7 +101,7 @@ void receiveMavlink() {
 	mavlink_status_t status;
 	for (int i = 0; i < len; i++) {
 		if (mavlink_parse_char(MAVLINK_COMM_0, buf[i], &msg, &status)) {
-			mavlinkConnected = true;
+			mavlinkTime = t;
 			handleMavlink(&msg);
 		}
 	}

flix/wifi.ino

@@ -64,7 +64,7 @@ void sendWiFi(const uint8_t *buf, int len) {
 
 	if (WiFi.softAPgetStationNum() == 0 && !WiFi.isConnected()) return;
 
-	udp.beginPacket(udpRemoteIP, udpRemotePort);
+	udp.beginPacket(t - mavlinkTime < 5 ? udpRemoteIP : IPAddress(255, 255, 255, 255), udpRemotePort); // broadcast if lost connection
 	udp.write(buf, len);
 	udp.endPacket();
 }
@@ -113,7 +113,7 @@ void printWiFiInfo() {
 	} else {
 		print("Mode: Disabled\n");
 	}
-	print("MAVLink connected: %d\n", mavlinkConnected);
+	print("MAVLink connected: %d\n", valid(mavlinkTime));
 }
 
 void configWiFi(int mode, const char *first, const char *second) {