Fix stack allocation (now probably too large) for PX4IO debugging. Disable...

Fix stack allocation (now probably too large) for PX4IO debugging.  Disable nonblocking serial comms to avoid losing tx data.

apps/px4/px4io/driver/px4io.cpp

@@ -234,7 +234,7 @@ PX4IO::init()
 	}
 
 	/* start the IO interface task */
-	_task = task_create("px4io", SCHED_PRIORITY_DEFAULT, 1024, (main_t)&PX4IO::task_main_trampoline, nullptr);
+	_task = task_create("px4io", SCHED_PRIORITY_DEFAULT, 4096, (main_t)&PX4IO::task_main_trampoline, nullptr);
 	if (_task < 0) {
 		debug("task start failed: %d", errno);
 		return -errno;
@@ -255,7 +255,7 @@ PX4IO::task_main()
 	log("starting");
 
 	/* open the serial port */
-	_serial_fd = ::open("/dev/ttyS2", O_RDWR | O_NONBLOCK);
+	_serial_fd = ::open("/dev/ttyS2", O_RDWR);
 	if (_serial_fd < 0) {
 		debug("failed to open serial port for IO: %d", errno);
 		_task = -1;
@@ -300,11 +300,13 @@ PX4IO::task_main()
 	fds[2].fd = _t_armed;
 	fds[2].events = POLLIN;
 
+	log("ready");
+
 	/* loop handling received serial bytes */
 	while (!_task_should_exit) {
 
 		/* sleep waiting for data, but no more than 100ms */
-		int ret = ::poll(&fds[0], 1, 100);
+		int ret = ::poll(&fds[0], sizeof(fds) / sizeof(fds[0]), 1000);
 
 		/* this would be bad... */
 		if (ret < 0) {
@@ -342,6 +344,7 @@ PX4IO::task_main()
 				}
 			}
 			if (fds[2].revents & POLLIN) {
+
 				orb_copy(ORB_ID(actuator_armed), _t_armed, &_controls);
 				_send_needed = true;
 			}
@@ -374,11 +377,19 @@ PX4IO::control_callback(uintptr_t handle,
 void
 PX4IO::io_recv()
 {
-	uint8_t c;
+	uint8_t buf[32];
+	int count;
+
+	/*
+	 * We are here because poll says there is some data, so this
+	 * won't block even on a blocking device.  If more bytes are
+	 * available, we'll go back to poll() again...
+	 */
+	count = ::read(_serial_fd, buf, sizeof(buf));
 
-	/* handle bytes from IO */
-	while (::read(_serial_fd, &c, 1) == 1)
-		hx_stream_rx(_io_stream, c);
+	/* pass received bytes to the packet decoder */
+	for (int i = 0; i < count; i++)
+		hx_stream_rx(_io_stream, buf[i]);
 }
 
 void
@@ -402,7 +413,6 @@ PX4IO::rx_callback(const uint8_t *buffer, size_t bytes_received)
 	_switch_armed = rep->armed;
 
 	unlock();
-
 }
 
 void