POSIX: change pthreads to px4_tasks in simulator

The simulator was using pthread APIs directly so calls to px4_getpid()
would fail since the task ID was not known. Changed simulator to use
px4_task_spawn_cmd.

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

src/modules/simulator/simulator_mavlink.cpp

@@ -33,6 +33,7 @@
 #include <termios.h>
 #include <px4_log.h>
 #include <px4_time.h>
+#include <px4_tasks.h>
 #include "simulator.h"
 #include "errno.h"
 #include <drivers/drv_pwm_output.h>
@@ -250,9 +251,9 @@ void Simulator::poll_actuators() {
 	}
 }
 
-void *Simulator::sending_trampoline(void *) {
+int  Simulator::sending_trampoline(int argv, char *argc[]) {
 	_instance->send();
-	return 0;	// why do I have to put this???
+	return 0;
 }
 
 void Simulator::send() {
@@ -326,21 +327,6 @@ void Simulator::updateSamples()
 		return;
 	}
 
-	// create a thread for sending data to the simulator
-	pthread_t sender_thread;
-
-	// initialize threads
-	pthread_attr_t sender_thread_attr;
-	pthread_attr_init(&sender_thread_attr);
-	pthread_attr_setstacksize(&sender_thread_attr, 1000);
-
-	struct sched_param param;
-	(void)pthread_attr_getschedparam(&sender_thread_attr, &param);
-
-	/* low priority */
-	param.sched_priority = SCHED_PRIORITY_DEFAULT;
-	(void)pthread_attr_setschedparam(&sender_thread_attr, &param);
-
 	// setup serial connection to autopilot (used to get manual controls)
 	int serial_fd = openUart(PIXHAWK_DEVICE, 115200);
 
@@ -381,9 +367,15 @@ void Simulator::updateSamples()
 	// subscribe to topics
 	_actuator_outputs_sub = orb_subscribe_multi(ORB_ID(actuator_outputs), 0);
 
+	char * argv[2] = { nullptr, nullptr };
+
 	// got data from simulator, now activate the sending thread
-	pthread_create(&sender_thread, &sender_thread_attr, Simulator::sending_trampoline, NULL);
-	pthread_attr_destroy(&sender_thread_attr);
+        px4_task_spawn_cmd("simulator-send",
+			   SCHED_DEFAULT,
+			   SCHED_PRIORITY_DEFAULT,
+			   1000,
+			   (px4_main_t)&Simulator::sending_trampoline,
+			   (char *const *)argv);
 
 	// wait for new mavlink messages to arrive
 	while (true) {