SITL: added -C option to desktop mode

this allows running APM to stdout, which is useful for test sketches

libraries/Desktop/support/FastSerial.cpp

@@ -70,6 +70,7 @@ static struct tcp_state {
 	int listen_fd;  // socket we are listening on
 	int fd;         // data socket
 	int serial_port;
+	bool console;
 } tcp_state[FS_MAX_PORTS];
 
 
@@ -85,6 +86,17 @@ static void tcp_start_connection(unsigned int serial_port, bool wait_for_connect
 	struct sockaddr_in sockaddr;
 	int ret;
 
+	if (desktop_state.console_mode) {
+		// hack for console access
+		s->connected = true;
+		s->listen_fd = -1;
+		s->fd = 1;
+		s->serial_port = serial_port;
+		s->console = true;
+		set_nonblocking(0);
+		return;
+	}
+
 	s->serial_port = serial_port;
 
 	memset(&sockaddr,0,sizeof(sockaddr));
@@ -291,6 +303,10 @@ int FastSerial::read(void)
 		return -1;
 	}
 
+	if (s->console) {
+		return ::read(0, &c, 1);
+	}
+
     int n = recv(s->fd, &c, 1, MSG_DONTWAIT | MSG_NOSIGNAL);
 	if (n <= 0) {
 		// the socket has reached EOF
@@ -326,7 +342,11 @@ void FastSerial::write(uint8_t c)
 	if (!desktop_state.slider) {
 		flags |= MSG_DONTWAIT;
 	}
-	send(s->fd, &c, 1, flags);
+	if (s->console) {
+		::write(s->fd, &c, 1);
+	} else {
+		send(s->fd, &c, 1, flags);
+	}
 }
 
 // Buffer management ///////////////////////////////////////////////////////////

libraries/Desktop/support/desktop.h

@@ -10,6 +10,7 @@ struct desktop_info {
 	bool quadcopter; // use quadcopter outputs
 	unsigned framerate;
 	float initial_height;
+	bool console_mode;
 };
 
 extern struct desktop_info desktop_state;

libraries/Desktop/support/main.cpp

@@ -29,6 +29,7 @@ static void usage(void)
 	printf("\t-w          wipe eeprom and dataflash\n");
 	printf("\t-r RATE     set SITL framerate\n");
 	printf("\t-H HEIGHT   initial barometric height\n");
+	printf("\t-C          use console instead of TCP ports\n");
 }
 
 int main(int argc, char * const argv[])
@@ -40,7 +41,7 @@ int main(int argc, char * const argv[])
 
 	signal(SIGFPE, sig_fpe);
 
-	while ((opt = getopt(argc, argv, "swhr:H:")) != -1) {
+	while ((opt = getopt(argc, argv, "swhr:H:C")) != -1) {
 		switch (opt) {
 		case 's':
 			desktop_state.slider = true;
@@ -55,6 +56,9 @@ int main(int argc, char * const argv[])
 		case 'H':
 			desktop_state.initial_height = atof(optarg);
 			break;
+		case 'C':
+			desktop_state.console_mode = true;
+			break;
 		default:
 			usage();
 			exit(1);