Merge branch 'master' into sdlog2

19 files changed, 1155 insertions, 90 deletions

diff --git a/ROMFS/px4fmu_common/mixers/IO_pass.mix b/ROMFS/px4fmu_common/mixers/IO_pass.mix
new file mode 100644
index 000000000..39f875ddb
--- /dev/null
+++ b/ROMFS/px4fmu_common/mixers/IO_pass.mix
@@ -0,0 +1,38 @@
+Passthrough mixer for PX4IO
+============================
+
+This file defines passthrough mixers suitable for testing.
+
+Channel group 0, channels 0-7 are passed directly through to the outputs.
+
+M: 1
+O:      10000  10000      0 -10000  10000
+S: 0 0  10000  10000      0 -10000  10000
+
+M: 1
+O:      10000  10000      0 -10000  10000
+S: 0 1  10000  10000      0 -10000  10000
+
+M: 1
+O:      10000  10000      0 -10000  10000
+S: 0 2  10000  10000      0 -10000  10000
+
+M: 1
+O:      10000  10000      0 -10000  10000
+S: 0 3  10000  10000      0 -10000  10000
+
+M: 1
+O:      10000  10000      0 -10000  10000
+S: 0 4  10000  10000      0 -10000  10000
+
+M: 1
+O:      10000  10000      0 -10000  10000
+S: 0 5  10000  10000      0 -10000  10000
+
+M: 1
+O:      10000  10000      0 -10000  10000
+S: 0 6  10000  10000      0 -10000  10000
+
+M: 1
+O:      10000  10000      0 -10000  10000
+S: 0 7  10000  10000      0 -10000  10000
diff --git a/makefiles/config_px4fmu_default.mk b/makefiles/config_px4fmu_default.mk
index 53f371f90..d50eb1e50 100644
--- a/makefiles/config_px4fmu_default.mk
+++ b/makefiles/config_px4fmu_default.mk
@@ -62,7 +62,8 @@ MODULES		+= modules/gpio_led
 # Estimation modules (EKF / other filters)
 #
 MODULES		+= modules/attitude_estimator_ekf
-MODULES		+= modules/position_estimator_mc
+MODULES		+= modules/attitude_estimator_so3_comp
+#MODULES		+= modules/position_estimator_mc
 MODULES		+= modules/position_estimator
 MODULES		+= modules/att_pos_estimator_ekf
 
diff --git a/makefiles/firmware.mk b/makefiles/firmware.mk
index 6b09e6ec3..f1c1b496a 100644
--- a/makefiles/firmware.mk
+++ b/makefiles/firmware.mk
@@ -177,6 +177,12 @@ GLOBAL_DEPS		+= $(MAKEFILE_LIST)
 EXTRA_CLEANS		 = 
 
 ################################################################################
+# NuttX libraries and paths
+################################################################################
+
+include $(PX4_MK_DIR)/nuttx.mk
+
+################################################################################
 # Modules
 ################################################################################
 
@@ -297,12 +303,6 @@ $(LIBRARY_CLEANS):
 	clean
 
 ################################################################################
-# NuttX libraries and paths
-################################################################################
-
-include $(PX4_MK_DIR)/nuttx.mk
-
-################################################################################
 # ROMFS generation
 ################################################################################
 
diff --git a/makefiles/nuttx.mk b/makefiles/nuttx.mk
index 346735a02..d283096b2 100644
--- a/makefiles/nuttx.mk
+++ b/makefiles/nuttx.mk
@@ -69,10 +69,14 @@ INCLUDE_DIRS		+= $(NUTTX_EXPORT_DIR)include \
 
 LIB_DIRS		+= $(NUTTX_EXPORT_DIR)libs
 LIBS			+= -lapps -lnuttx
-LINK_DEPS		+= $(NUTTX_EXPORT_DIR)libs/libapps.a \
+NUTTX_LIBS		 = $(NUTTX_EXPORT_DIR)libs/libapps.a \
 			   $(NUTTX_EXPORT_DIR)libs/libnuttx.a
+LINK_DEPS		+= $(NUTTX_LIBS)
 
 $(NUTTX_CONFIG_HEADER):	$(NUTTX_ARCHIVE)
 	@$(ECHO) %% Unpacking $(NUTTX_ARCHIVE)
 	$(Q) $(UNZIP_CMD) -q -o -d $(WORK_DIR) $(NUTTX_ARCHIVE)
 	$(Q) $(TOUCH) $@
+
+ $(LDSCRIPT): $(NUTTX_CONFIG_HEADER)
+ $(NUTTX_LIBS): $(NUTTX_CONFIG_HEADER)
diff --git a/makefiles/toolchain_gnu-arm-eabi.mk b/makefiles/toolchain_gnu-arm-eabi.mk
index c75a08bd1..99c2776fd 100644
--- a/makefiles/toolchain_gnu-arm-eabi.mk
+++ b/makefiles/toolchain_gnu-arm-eabi.mk
@@ -70,6 +70,14 @@ ARCHCPUFLAGS_CORTEXM3	 = -mcpu=cortex-m3 \
 			   -march=armv7-m \
 			   -mfloat-abi=soft
 
+ARCHINSTRUMENTATIONDEFINES_CORTEXM4F = -finstrument-functions \
+			   -ffixed-r10
+
+ARCHINSTRUMENTATIONDEFINES_CORTEXM4 = -finstrument-functions \
+			   -ffixed-r10
+
+ARCHINSTRUMENTATIONDEFINES_CORTEXM3 = 
+
 # Pick the right set of flags for the architecture.
 #
 ARCHCPUFLAGS		 = $(ARCHCPUFLAGS_$(CONFIG_ARCH))
@@ -91,8 +99,8 @@ ARCHOPTIMIZATION	 = $(MAXOPTIMIZATION) \
 
 # enable precise stack overflow tracking
 # note - requires corresponding support in NuttX
-INSTRUMENTATIONDEFINES	 = -finstrument-functions \
-			   -ffixed-r10
+INSTRUMENTATIONDEFINES	 = $(ARCHINSTRUMENTATIONDEFINES_$(CONFIG_ARCH))
+
 # Language-specific flags
 #
 ARCHCFLAGS		 = -std=gnu99
diff --git a/nuttx/configs/px4fmu/nsh/defconfig b/nuttx/configs/px4fmu/nsh/defconfig
index 02e224302..0662f7fbe 100755
--- a/nuttx/configs/px4fmu/nsh/defconfig
+++ b/nuttx/configs/px4fmu/nsh/defconfig
@@ -248,7 +248,7 @@ CONFIG_SERIAL_TERMIOS=y
 CONFIG_SERIAL_CONSOLE_REINIT=y
 CONFIG_STANDARD_SERIAL=y
 
-CONFIG_USART1_SERIAL_CONSOLE=y
+CONFIG_USART1_SERIAL_CONSOLE=n
 CONFIG_USART2_SERIAL_CONSOLE=n
 CONFIG_USART3_SERIAL_CONSOLE=n
 CONFIG_UART4_SERIAL_CONSOLE=n
@@ -561,7 +561,7 @@ CONFIG_START_MONTH=1
 CONFIG_START_DAY=1
 CONFIG_GREGORIAN_TIME=n
 CONFIG_JULIAN_TIME=n
-CONFIG_DEV_CONSOLE=y
+CONFIG_DEV_CONSOLE=n
 CONFIG_DEV_LOWCONSOLE=n
 CONFIG_MUTEX_TYPES=n
 CONFIG_PRIORITY_INHERITANCE=y
@@ -717,7 +717,7 @@ CONFIG_ARCH_BZERO=n
 #   zero for all dynamic allocations.
 #
 CONFIG_MAX_TASKS=32
-CONFIG_MAX_TASK_ARGS=8
+CONFIG_MAX_TASK_ARGS=10
 CONFIG_NPTHREAD_KEYS=4
 CONFIG_NFILE_DESCRIPTORS=32
 CONFIG_NFILE_STREAMS=25
@@ -925,7 +925,7 @@ CONFIG_USBDEV_TRACE_NRECORDS=512
 #   Size of the serial receive/transmit buffers. Default 256.
 #
 CONFIG_CDCACM=y
-CONFIG_CDCACM_CONSOLE=n
+CONFIG_CDCACM_CONSOLE=y
 #CONFIG_CDCACM_EP0MAXPACKET
 CONFIG_CDCACM_EPINTIN=1
 #CONFIG_CDCACM_EPINTIN_FSSIZE
diff --git a/src/drivers/hott_telemetry/hott_telemetry_main.c b/src/drivers/hott_telemetry/hott_telemetry_main.c
index 4318244f8..1d2bdd92e 100644
--- a/src/drivers/hott_telemetry/hott_telemetry_main.c
+++ b/src/drivers/hott_telemetry/hott_telemetry_main.c
@@ -133,15 +133,14 @@ recv_req_id(int uart, uint8_t *id)
 	if (poll(fds, 1, timeout_ms) > 0) {
 		/* Get the mode: binary or text  */
 		read(uart, &mode, sizeof(mode));
-		/* Read the device ID being polled */
-		read(uart, id, sizeof(*id));
 
 		/* if we have a binary mode request */
 		if (mode != BINARY_MODE_REQUEST_ID) {
-			warnx("Non binary request ID detected: %d", mode);
 			return ERROR;
 		}
 
+		/* Read the device ID being polled */
+		read(uart, id, sizeof(*id));
 	} else {
 		warnx("UART timeout on TX/RX port");
 		return ERROR;
@@ -216,9 +215,15 @@ hott_telemetry_thread_main(int argc, char *argv[])
 	uint8_t buffer[MESSAGE_BUFFER_SIZE];
 	size_t size = 0;
 	uint8_t id = 0;
+	bool connected = true;
 
 	while (!thread_should_exit) {
 		if (recv_req_id(uart, &id) == OK) {
+			if (!connected) {
+				connected = true;
+				warnx("OK");
+			}
+
 			switch (id) {
 			case EAM_SENSOR_ID:
 				build_eam_response(buffer, &size);
@@ -234,7 +239,8 @@ hott_telemetry_thread_main(int argc, char *argv[])
 
 			send_data(uart, buffer, size);
 		} else {
-			warnx("NOK");
+			connected = false;
+			warnx("syncing");
 		}
 	}
 
diff --git a/src/drivers/px4io/px4io.cpp b/src/drivers/px4io/px4io.cpp
index 0934e614b..19163cebe 100644
--- a/src/drivers/px4io/px4io.cpp
+++ b/src/drivers/px4io/px4io.cpp
@@ -1302,7 +1302,7 @@ PX4IO::print_status()
 	       io_reg_get(PX4IO_PAGE_STATUS, PX4IO_P_STATUS_VBATT),
 	       io_reg_get(PX4IO_PAGE_STATUS, PX4IO_P_STATUS_IBATT),
 	       io_reg_get(PX4IO_PAGE_SETUP, PX4IO_P_SETUP_VBATT_SCALE));
-	printf("amp_per_volt %.3f amp_offset %.3f mAhDischarged %.3f\n",
+	printf("amp_per_volt %.3f amp_offset %.3f mAh discharged %.3f\n",
 	       (double)_battery_amp_per_volt,
 	       (double)_battery_amp_bias,
 	       (double)_battery_mamphour_total);
@@ -1496,7 +1496,7 @@ PX4IO::ioctl(file *filep, int cmd, unsigned long arg)
 
 	case MIXERIOCLOADBUF: {
 		const char *buf = (const char *)arg;
-		ret = mixer_send(buf, strnlen(buf, 1024));
+		ret = mixer_send(buf, strnlen(buf, 2048));
 		break;
 	}
 
@@ -1637,6 +1637,13 @@ test(void)
 	if (ioctl(fd, PWM_SERVO_ARM, 0))
 		err(1, "failed to arm servos");
 
+	/* Open console directly to grab CTRL-C signal */
+	int console = open("/dev/console", O_NONBLOCK | O_RDONLY | O_NOCTTY);
+	if (!console)
+		err(1, "failed opening console");
+
+	warnx("Press CTRL-C or 'c' to abort.");
+
 	for (;;) {
 
 		/* sweep all servos between 1000..2000 */
@@ -1671,6 +1678,16 @@ test(void)
 			if (value != servos[i])
 				errx(1, "servo %d readback error, got %u expected %u", i, value, servos[i]);
 		}
+
+		/* Check if user wants to quit */
+		char c;
+		if (read(console, &c, 1) == 1) {
+			if (c == 0x03 || c == 0x63) {
+				warnx("User abort\n");
+				close(console);
+				exit(0);
+			}
+		}
 	}
 }
 
diff --git a/src/examples/px4_daemon_app/px4_daemon_app.c b/src/examples/px4_daemon_app/px4_daemon_app.c
index a5d847777..c568aaadc 100644
--- a/src/examples/px4_daemon_app/px4_daemon_app.c
+++ b/src/examples/px4_daemon_app/px4_daemon_app.c
@@ -1,7 +1,6 @@
 /****************************************************************************
  *
- *   Copyright (C) 2012 PX4 Development Team. All rights reserved.
- *   Author: @author Example User <mail@example.com>
+ *   Copyright (c) 2012, 2013 PX4 Development Team. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -33,27 +32,33 @@
  ****************************************************************************/
 
 /**
- * @file px4_deamon_app.c
- * Deamon application example for PX4 autopilot
+ * @file px4_daemon_app.c
+ * daemon application example for PX4 autopilot
+ * 
+ * @author Example User <mail@example.com>
  */
 
 #include <nuttx/config.h>
+#include <nuttx/sched.h>
 #include <unistd.h>
 #include <stdio.h>
 
-static bool thread_should_exit = false;		/**< Deamon exit flag */
-static bool thread_running = false;		/**< Deamon status flag */
-static int deamon_task;				/**< Handle of deamon task / thread */
+#include <systemlib/systemlib.h>
+#include <systemlib/err.h>
+
+static bool thread_should_exit = false;		/**< daemon exit flag */
+static bool thread_running = false;		/**< daemon status flag */
+static int daemon_task;				/**< Handle of daemon task / thread */
 
 /**
- * Deamon management function.
+ * daemon management function.
  */
-__EXPORT int px4_deamon_app_main(int argc, char *argv[]);
+__EXPORT int px4_daemon_app_main(int argc, char *argv[]);
 
 /**
- * Mainloop of deamon.
+ * Mainloop of daemon.
  */
-int px4_deamon_thread_main(int argc, char *argv[]);
+int px4_daemon_thread_main(int argc, char *argv[]);
 
 /**
  * Print the correct usage.
@@ -64,20 +69,19 @@ static void
 usage(const char *reason)
 {
 	if (reason)
-		fprintf(stderr, "%s\n", reason);
-	fprintf(stderr, "usage: deamon {start|stop|status} [-p <additional params>]\n\n");
-	exit(1);
+		warnx("%s\n", reason);
+	errx(1, "usage: daemon {start|stop|status} [-p <additional params>]\n\n");
 }
 
 /**
- * The deamon app only briefly exists to start
+ * The daemon app only briefly exists to start
  * the background job. The stack size assigned in the
  * Makefile does only apply to this management task.
  * 
  * The actual stack size should be set in the call
  * to task_create().
  */
-int px4_deamon_app_main(int argc, char *argv[])
+int px4_daemon_app_main(int argc, char *argv[])
 {
 	if (argc < 1)
 		usage("missing command");
@@ -85,17 +89,17 @@ int px4_deamon_app_main(int argc, char *argv[])
 	if (!strcmp(argv[1], "start")) {
 
 		if (thread_running) {
-			printf("deamon already running\n");
+			warnx("daemon already running\n");
 			/* this is not an error */
 			exit(0);
 		}
 
 		thread_should_exit = false;
-		deamon_task = task_spawn("deamon",
+		daemon_task = task_spawn("daemon",
 					 SCHED_DEFAULT,
 					 SCHED_PRIORITY_DEFAULT,
 					 4096,
-					 px4_deamon_thread_main,
+					 px4_daemon_thread_main,
 					 (argv) ? (const char **)&argv[2] : (const char **)NULL);
 		exit(0);
 	}
@@ -107,9 +111,9 @@ int px4_deamon_app_main(int argc, char *argv[])
 
 	if (!strcmp(argv[1], "status")) {
 		if (thread_running) {
-			printf("\tdeamon app is running\n");
+			warnx("\trunning\n");
 		} else {
-			printf("\tdeamon app not started\n");
+			warnx("\tnot started\n");
 		}
 		exit(0);
 	}
@@ -118,18 +122,18 @@ int px4_deamon_app_main(int argc, char *argv[])
 	exit(1);
 }
 
-int px4_deamon_thread_main(int argc, char *argv[]) {
+int px4_daemon_thread_main(int argc, char *argv[]) {
 
-	printf("[deamon] starting\n");
+	warnx("[daemon] starting\n");
 
 	thread_running = true;
 
 	while (!thread_should_exit) {
-		printf("Hello Deamon!\n");
+		warnx("Hello daemon!\n");
 		sleep(10);
 	}
 
-	printf("[deamon] exiting.\n");
+	warnx("[daemon] exiting.\n");
 
 	thread_running = false;
 
diff --git a/src/modules/att_pos_estimator_ekf/kalman_main.cpp b/src/modules/att_pos_estimator_ekf/kalman_main.cpp
index aebe3d1fe..10592ec7c 100644
--- a/src/modules/att_pos_estimator_ekf/kalman_main.cpp
+++ b/src/modules/att_pos_estimator_ekf/kalman_main.cpp
@@ -44,6 +44,7 @@
 #include <string.h>
 #include <systemlib/systemlib.h>
 #include <systemlib/param/param.h>
+#include <systemlib/err.h>
 #include <drivers/drv_hrt.h>
 #include <math.h>
 #include "KalmanNav.hpp"
@@ -73,7 +74,7 @@ usage(const char *reason)
 	if (reason)
 		fprintf(stderr, "%s\n", reason);
 
-	fprintf(stderr, "usage: kalman_demo {start|stop|status} [-p <additional params>]\n\n");
+	warnx("usage: att_pos_estimator_ekf {start|stop|status} [-p <additional params>]");
 	exit(1);
 }
 
@@ -94,13 +95,13 @@ int att_pos_estimator_ekf_main(int argc, char *argv[])
 	if (!strcmp(argv[1], "start")) {
 
 		if (thread_running) {
-			printf("kalman_demo already running\n");
+			warnx("already running");
 			/* this is not an error */
 			exit(0);
 		}
 
 		thread_should_exit = false;
-		deamon_task = task_spawn("kalman_demo",
+		deamon_task = task_spawn("att_pos_estimator_ekf",
 					 SCHED_DEFAULT,
 					 SCHED_PRIORITY_MAX - 5,
 					 4096,
@@ -116,10 +117,10 @@ int att_pos_estimator_ekf_main(int argc, char *argv[])
 
 	if (!strcmp(argv[1], "status")) {
 		if (thread_running) {
-			printf("\tkalman_demo app is running\n");
+			warnx("is running\n");
 
 		} else {
-			printf("\tkalman_demo app not started\n");
+			warnx("not started\n");
 		}
 
 		exit(0);
@@ -132,7 +133,7 @@ int att_pos_estimator_ekf_main(int argc, char *argv[])
 int kalman_demo_thread_main(int argc, char *argv[])
 {
 
-	printf("[kalman_demo] starting\n");
+	warnx("starting\n");
 
 	using namespace math;
 
@@ -144,7 +145,7 @@ int kalman_demo_thread_main(int argc, char *argv[])
 		nav.update();
 	}
 
-	printf("[kalman_demo] exiting.\n");
+	printf("exiting.\n");
 
 	thread_running = false;
 
diff --git a/src/modules/attitude_estimator_so3_comp/README b/src/modules/attitude_estimator_so3_comp/README
new file mode 100644
index 000000000..79c50a531
--- /dev/null
+++ b/src/modules/attitude_estimator_so3_comp/README
@@ -0,0 +1,5 @@
+Synopsis
+
+ nsh> attitude_estimator_so3_comp start -d /dev/ttyS1 -b 115200
+
+Option -d is for debugging packet. See code for detailed packet structure.
diff --git a/src/modules/attitude_estimator_so3_comp/attitude_estimator_so3_comp_main.cpp b/src/modules/attitude_estimator_so3_comp/attitude_estimator_so3_comp_main.cpp
new file mode 100755
index 000000000..3cbc62ea1
--- /dev/null
+++ b/src/modules/attitude_estimator_so3_comp/attitude_estimator_so3_comp_main.cpp
@@ -0,0 +1,833 @@
+/*
+ * Author: Hyon Lim <limhyon@gmail.com, hyonlim@snu.ac.kr>
+ *
+ * @file attitude_estimator_so3_comp_main.c
+ *
+ * Implementation of nonlinear complementary filters on the SO(3).
+ * This code performs attitude estimation by using accelerometer, gyroscopes and magnetometer.
+ * Result is provided as quaternion, 1-2-3 Euler angle and rotation matrix.
+ * 
+ * Theory of nonlinear complementary filters on the SO(3) is based on [1].
+ * Quaternion realization of [1] is based on [2].
+ * Optmized quaternion update code is based on Sebastian Madgwick's implementation.
+ * 
+ * References
+ *  [1] Mahony, R.; Hamel, T.; Pflimlin, Jean-Michel, "Nonlinear Complementary Filters on the Special Orthogonal Group," Automatic Control, IEEE Transactions on , vol.53, no.5, pp.1203,1218, June 2008
+ *  [2] Euston, M.; Coote, P.; Mahony, R.; Jonghyuk Kim; Hamel, T., "A complementary filter for attitude estimation of a fixed-wing UAV," Intelligent Robots and Systems, 2008. IROS 2008. IEEE/RSJ International Conference on , vol., no., pp.340,345, 22-26 Sept. 2008
+ */
+
+#include <nuttx/config.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdbool.h>
+#include <poll.h>
+#include <fcntl.h>
+#include <float.h>
+#include <nuttx/sched.h>
+#include <sys/prctl.h>
+#include <termios.h>
+#include <errno.h>
+#include <limits.h>
+#include <math.h>
+#include <uORB/uORB.h>
+#include <uORB/topics/debug_key_value.h>
+#include <uORB/topics/sensor_combined.h>
+#include <uORB/topics/vehicle_attitude.h>
+#include <uORB/topics/vehicle_status.h>
+#include <uORB/topics/parameter_update.h>
+#include <drivers/drv_hrt.h>
+
+#include <systemlib/systemlib.h>
+#include <systemlib/perf_counter.h>
+#include <systemlib/err.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+#include "attitude_estimator_so3_comp_params.h"
+#ifdef __cplusplus
+}
+#endif
+
+extern "C" __EXPORT int attitude_estimator_so3_comp_main(int argc, char *argv[]);
+
+static bool thread_should_exit = false;		/**< Deamon exit flag */
+static bool thread_running = false;		/**< Deamon status flag */
+static int attitude_estimator_so3_comp_task;				/**< Handle of deamon task / thread */
+static float q0 = 1.0f, q1 = 0.0f, q2 = 0.0f, q3 = 0.0f;	/** quaternion of sensor frame relative to auxiliary frame */
+static float dq0 = 0.0f, dq1 = 0.0f, dq2 = 0.0f, dq3 = 0.0f;	/** quaternion of sensor frame relative to auxiliary frame */
+static float gyro_bias[3] = {0.0f, 0.0f, 0.0f}; /** bias estimation */
+static bool bFilterInit = false;
+
+//! Auxiliary variables to reduce number of repeated operations
+static float q0q0, q0q1, q0q2, q0q3;
+static float q1q1, q1q2, q1q3;
+static float q2q2, q2q3;
+static float q3q3;
+
+//! Serial packet related
+static int uart;
+static int baudrate;
+
+/**
+ * Mainloop of attitude_estimator_so3_comp.
+ */
+int attitude_estimator_so3_comp_thread_main(int argc, char *argv[]);
+
+/**
+ * Print the correct usage.
+ */
+static void usage(const char *reason);
+
+static void
+usage(const char *reason)
+{
+	if (reason)
+		fprintf(stderr, "%s\n", reason);
+
+	fprintf(stderr, "usage: attitude_estimator_so3_comp {start|stop|status} [-d <devicename>] [-b <baud rate>]\n"
+		"-d and -b options are for separate visualization with raw data (quaternion packet) transfer\n"
+		"ex) attitude_estimator_so3_comp start -d /dev/ttyS1 -b 115200\n");
+	exit(1);
+}
+
+/**
+ * The attitude_estimator_so3_comp app only briefly exists to start
+ * the background job. The stack size assigned in the
+ * Makefile does only apply to this management task.
+ *
+ * The actual stack size should be set in the call
+ * to task_create().
+ */
+int attitude_estimator_so3_comp_main(int argc, char *argv[])
+{
+	if (argc < 1)
+		usage("missing command");
+
+	
+
+	if (!strcmp(argv[1], "start")) {
+
+		if (thread_running) {
+			printf("attitude_estimator_so3_comp already running\n");
+			/* this is not an error */
+			exit(0);
+		}
+
+		thread_should_exit = false;
+		attitude_estimator_so3_comp_task = task_spawn("attitude_estimator_so3_comp",
+					      SCHED_DEFAULT,
+					      SCHED_PRIORITY_MAX - 5,
+					      12400,
+					      attitude_estimator_so3_comp_thread_main,
+					      (const char **)argv);
+		exit(0);
+	}
+
+	if (!strcmp(argv[1], "stop")) {
+		thread_should_exit = true;
+
+		while(thread_running){
+			usleep(200000);
+			printf(".");
+		}
+		printf("terminated.");
+		exit(0);
+	}
+
+	if (!strcmp(argv[1], "status")) {
+		if (thread_running) {
+			printf("\tattitude_estimator_so3_comp app is running\n");
+
+		} else {
+			printf("\tattitude_estimator_so3_comp app not started\n");
+		}
+
+		exit(0);
+	}
+
+	usage("unrecognized command");
+	exit(1);
+}
+
+//---------------------------------------------------------------------------------------------------
+// Fast inverse square-root
+// See: http://en.wikipedia.org/wiki/Fast_inverse_square_root
+float invSqrt(float number) {
+    volatile long i;
+    volatile float x, y;
+    volatile const float f = 1.5F;
+
+    x = number * 0.5F;
+    y = number;
+    i = * (( long * ) &y);
+    i = 0x5f375a86 - ( i >> 1 );
+    y = * (( float * ) &i);
+    y = y * ( f - ( x * y * y ) );
+    return y;
+}
+
+//! Using accelerometer, sense the gravity vector.
+//! Using magnetometer, sense yaw.
+void NonlinearSO3AHRSinit(float ax, float ay, float az, float mx, float my, float mz)
+{
+    float initialRoll, initialPitch;
+    float cosRoll, sinRoll, cosPitch, sinPitch;
+    float magX, magY;
+    float initialHdg, cosHeading, sinHeading;
+
+    initialRoll = atan2(-ay, -az);
+    initialPitch = atan2(ax, -az);
+
+    cosRoll = cosf(initialRoll);
+    sinRoll = sinf(initialRoll);
+    cosPitch = cosf(initialPitch);
+    sinPitch = sinf(initialPitch);
+
+    magX = mx * cosPitch + my * sinRoll * sinPitch + mz * cosRoll * sinPitch;
+
+    magY = my * cosRoll - mz * sinRoll;
+
+    initialHdg = atan2f(-magY, magX);
+
+    cosRoll = cosf(initialRoll * 0.5f);
+    sinRoll = sinf(initialRoll * 0.5f);
+
+    cosPitch = cosf(initialPitch * 0.5f);
+    sinPitch = sinf(initialPitch * 0.5f);
+
+    cosHeading = cosf(initialHdg * 0.5f);
+    sinHeading = sinf(initialHdg * 0.5f);
+
+    q0 = cosRoll * cosPitch * cosHeading + sinRoll * sinPitch * sinHeading;
+    q1 = sinRoll * cosPitch * cosHeading - cosRoll * sinPitch * sinHeading;
+    q2 = cosRoll * sinPitch * cosHeading + sinRoll * cosPitch * sinHeading;
+    q3 = cosRoll * cosPitch * sinHeading - sinRoll * sinPitch * cosHeading;
+
+    // auxillary variables to reduce number of repeated operations, for 1st pass
+    q0q0 = q0 * q0;
+    q0q1 = q0 * q1;
+    q0q2 = q0 * q2;
+    q0q3 = q0 * q3;
+    q1q1 = q1 * q1;
+    q1q2 = q1 * q2;
+    q1q3 = q1 * q3;
+    q2q2 = q2 * q2;
+    q2q3 = q2 * q3;
+    q3q3 = q3 * q3;
+}
+
+void NonlinearSO3AHRSupdate(float gx, float gy, float gz, float ax, float ay, float az, float mx, float my, float mz, float twoKp, float twoKi, float dt) {
+	float recipNorm;
+	float halfex = 0.0f, halfey = 0.0f, halfez = 0.0f;
+
+	//! Make filter converge to initial solution faster
+	//! This function assumes you are in static position.
+	//! WARNING : in case air reboot, this can cause problem. But this is very
+	//!	      unlikely happen.
+	if(bFilterInit == false)
+	{
+		NonlinearSO3AHRSinit(ax,ay,az,mx,my,mz);
+		bFilterInit = true;
+	}
+        	
+	//! If magnetometer measurement is available, use it.
+	if((mx == 0.0f) && (my == 0.0f) && (mz == 0.0f)) {
+		float hx, hy, hz, bx, bz;
+		float halfwx, halfwy, halfwz;
+	
+		// Normalise magnetometer measurement
+		// Will sqrt work better? PX4 system is powerful enough?
+    		recipNorm = invSqrt(mx * mx + my * my + mz * mz);
+    		mx *= recipNorm;
+    		my *= recipNorm;
+    		mz *= recipNorm;
+    
+    		// Reference direction of Earth's magnetic field
+    		hx = 2.0f * (mx * (0.5f - q2q2 - q3q3) + my * (q1q2 - q0q3) + mz * (q1q3 + q0q2));
+    		hy = 2.0f * (mx * (q1q2 + q0q3) + my * (0.5f - q1q1 - q3q3) + mz * (q2q3 - q0q1));
+		hz = 2 * mx * (q1q3 - q0q2) + 2 * my * (q2q3 + q0q1) + 2 * mz * (0.5 - q1q1 - q2q2);
+    		bx = sqrt(hx * hx + hy * hy);
+    		bz = hz;
+    
+    		// Estimated direction of magnetic field
+    		halfwx = bx * (0.5f - q2q2 - q3q3) + bz * (q1q3 - q0q2);
+    		halfwy = bx * (q1q2 - q0q3) + bz * (q0q1 + q2q3);
+    		halfwz = bx * (q0q2 + q1q3) + bz * (0.5f - q1q1 - q2q2);
+    
+    		// Error is sum of cross product between estimated direction and measured direction of field vectors
+    		halfex += (my * halfwz - mz * halfwy);
+    		halfey += (mz * halfwx - mx * halfwz);
+    		halfez += (mx * halfwy - my * halfwx);
+	}
+
+	// Compute feedback only if accelerometer measurement valid (avoids NaN in accelerometer normalisation)
+	if(!((ax == 0.0f) && (ay == 0.0f) && (az == 0.0f))) {
+		float halfvx, halfvy, halfvz;
+	
+		// Normalise accelerometer measurement
+		recipNorm = invSqrt(ax * ax + ay * ay + az * az);
+		ax *= recipNorm;
+		ay *= recipNorm;
+		az *= recipNorm;
+
+		// Estimated direction of gravity and magnetic field
+		halfvx = q1q3 - q0q2;
+		halfvy = q0q1 + q2q3;
+		halfvz = q0q0 - 0.5f + q3q3;
+	
+		// Error is sum of cross product between estimated direction and measured direction of field vectors
+		halfex += ay * halfvz - az * halfvy;
+		halfey += az * halfvx - ax * halfvz;
+		halfez += ax * halfvy - ay * halfvx;
+	}
+
+	// Apply feedback only when valid data has been gathered from the accelerometer or magnetometer
+	if(halfex != 0.0f && halfey != 0.0f && halfez != 0.0f) {
+		// Compute and apply integral feedback if enabled
+		if(twoKi > 0.0f) {
+			gyro_bias[0] += twoKi * halfex * dt;	// integral error scaled by Ki
+			gyro_bias[1] += twoKi * halfey * dt;
+			gyro_bias[2] += twoKi * halfez * dt;
+			gx += gyro_bias[0];	// apply integral feedback
+			gy += gyro_bias[1];
+			gz += gyro_bias[2];
+		}
+		else {
+			gyro_bias[0] = 0.0f;	// prevent integral windup
+			gyro_bias[1] = 0.0f;
+			gyro_bias[2] = 0.0f;
+		}
+
+		// Apply proportional feedback
+		gx += twoKp * halfex;
+		gy += twoKp * halfey;
+		gz += twoKp * halfez;
+	}
+	
+	//! Integrate rate of change of quaternion
+#if 0
+	gx *= (0.5f * dt);		// pre-multiply common factors
+	gy *= (0.5f * dt);
+	gz *= (0.5f * dt);
+#endif 
+
+	// Time derivative of quaternion. q_dot = 0.5*q\otimes omega.
+	//! q_k = q_{k-1} + dt*\dot{q}
+	//! \dot{q} = 0.5*q \otimes P(\omega)
+	dq0 = 0.5f*(-q1 * gx - q2 * gy - q3 * gz);
+	dq1 = 0.5f*(q0 * gx + q2 * gz - q3 * gy);
+	dq2 = 0.5f*(q0 * gy - q1 * gz + q3 * gx);
+	dq3 = 0.5f*(q0 * gz + q1 * gy - q2 * gx); 
+
+	q0 += dt*dq0;
+	q1 += dt*dq1;
+	q2 += dt*dq2;
+	q3 += dt*dq3;
+	
+	// Normalise quaternion
+	recipNorm = invSqrt(q0 * q0 + q1 * q1 + q2 * q2 + q3 * q3);
+	q0 *= recipNorm;
+	q1 *= recipNorm;
+	q2 *= recipNorm;
+	q3 *= recipNorm;
+
+	// Auxiliary variables to avoid repeated arithmetic
+        q0q0 = q0 * q0;
+       	q0q1 = q0 * q1;
+       	q0q2 = q0 * q2;
+       	q0q3 = q0 * q3;
+       	q1q1 = q1 * q1;
+       	q1q2 = q1 * q2;
+   	q1q3 = q1 * q3;
+       	q2q2 = q2 * q2;
+       	q2q3 = q2 * q3;
+       	q3q3 = q3 * q3;   
+}
+
+void send_uart_byte(char c)
+{
+	write(uart,&c,1);
+}
+
+void send_uart_bytes(uint8_t *data, int length)
+{
+	write(uart,data,(size_t)(sizeof(uint8_t)*length));
+}
+
+void send_uart_float(float f) {
+  uint8_t * b = (uint8_t *) &f;
+
+  //! Assume float is 4-bytes
+  for(int i=0; i<4; i++) {
+    
+    uint8_t b1 = (b[i] >> 4) & 0x0f;
+    uint8_t b2 = (b[i] & 0x0f);
+    
+    uint8_t c1 = (b1 < 10) ? ('0' + b1) : 'A' + b1 - 10;
+    uint8_t c2 = (b2 < 10) ? ('0' + b2) : 'A' + b2 - 10;
+    
+    send_uart_bytes(&c1,1);
+    send_uart_bytes(&c2,1);
+  }
+}
+
+void send_uart_float_arr(float *arr, int length)
+{
+	for(int i=0;i<length;++i)
+	{
+		send_uart_float(arr[i]);
+		send_uart_byte(',');
+	}
+}
+
+int open_uart(int baud, const char *uart_name, struct termios *uart_config_original, bool *is_usb)
+{
+	int speed;
+	
+	switch (baud) {
+        case 0:      speed = B0;      break;
+        case 50:     speed = B50;     break;
+        case 75:     speed = B75;     break;
+        case 110:    speed = B110;    break;
+        case 134:    speed = B134;    break;
+        case 150:    speed = B150;    break;
+        case 200:    speed = B200;    break;
+        case 300:    speed = B300;    break;
+        case 600:    speed = B600;    break;
+        case 1200:   speed = B1200;   break;
+        case 1800:   speed = B1800;   break;
+        case 2400:   speed = B2400;   break;
+        case 4800:   speed = B4800;   break;
+        case 9600:   speed = B9600;   break;
+        case 19200:  speed = B19200;  break;
+        case 38400:  speed = B38400;  break;
+        case 57600:  speed = B57600;  break;
+        case 115200: speed = B115200; break;
+        case 230400: speed = B230400; break;
+        case 460800: speed = B460800; break;
+        case 921600: speed = B921600; break;
+        default:
+                printf("ERROR: Unsupported baudrate: %d\n\tsupported examples:\n\n\t9600\n19200\n38400\n57600\n115200\n230400\n460800\n921600\n\n", baud);
+                return -EINVAL;
+        }
+
+	printf("[so3_comp_filt] UART is %s, baudrate is %d\n", uart_name, baud);
+        uart = open(uart_name, O_RDWR | O_NOCTTY);
+
+	/* Try to set baud rate */
+        struct termios uart_config;
+        int termios_state;
+        *is_usb = false;
+
+	/* make some wild guesses including that USB serial is indicated by either /dev/ttyACM0 or /dev/console */
+        if (strcmp(uart_name, "/dev/ttyACM0") != OK && strcmp(uart_name, "/dev/console") != OK) {
+                /* Back up the original uart configuration to restore it after exit */
+                if ((termios_state = tcgetattr(uart, uart_config_original)) < 0) {
+                        printf("ERROR getting baudrate / termios config for %s: %d\n", uart_name, termios_state);
+                        close(uart);
+                        return -1;
+                }
+
+                /* Fill the struct for the new configuration */
+                tcgetattr(uart, &uart_config);
+
+                /* Clear ONLCR flag (which appends a CR for every LF) */
+                uart_config.c_oflag &= ~ONLCR;
+
+                /* Set baud rate */
+                if (cfsetispeed(&uart_config, speed) < 0 || cfsetospeed(&uart_config, speed) < 0) {
+                        printf("ERROR setting baudrate / termios config for %s: %d (cfsetispeed, cfsetospeed)\n", uart_name, termios_state);
+                        close(uart);
+                        return -1;
+                }
+
+
+                if ((termios_state = tcsetattr(uart, TCSANOW, &uart_config)) < 0) {
+                        printf("ERROR setting baudrate / termios config for %s (tcsetattr)\n", uart_name);
+                        close(uart);
+                        return -1;
+                }
+
+        } else {
+                *is_usb = true;
+        }
+
+        return uart;
+}
+
+/*
+ * [Rot_matrix,x_aposteriori,P_aposteriori] = attitudeKalmanfilter(dt,z_k,x_aposteriori_k,P_aposteriori_k,knownConst)
+ */
+
+/*
+ * EKF Attitude Estimator main function.
+ *
+ * Estimates the attitude recursively once started.
+ *
+ * @param argc number of commandline arguments (plus command name)
+ * @param argv strings containing the arguments
+ */
+int attitude_estimator_so3_comp_thread_main(int argc, char *argv[])
+{
+
+const unsigned int loop_interval_alarm = 6500;	// loop interval in microseconds
+
+	//! Serial debug related
+	int ch;
+	struct termios uart_config_original;
+	bool usb_uart;
+	bool debug_mode = false;
+	char *device_name = "/dev/ttyS2";
+	baudrate = 115200;
+
+	//! Time constant
+	float dt = 0.005f;
+	
+	/* output euler angles */
+	float euler[3] = {0.0f, 0.0f, 0.0f};
+
+	float Rot_matrix[9] = {1.f,  0,  0,
+			      0,  1.f,  0,
+			      0,  0,  1.f
+			     };		/**< init: identity matrix */
+
+	float acc[3] = {0.0f, 0.0f, 0.0f};
+	float gyro[3] = {0.0f, 0.0f, 0.0f};
+	float mag[3] = {0.0f, 0.0f, 0.0f};
+
+	/* work around some stupidity in task_create's argv handling */
+	argc -= 2;
+	argv += 2;
+
+	//! -d <device_name>, default : /dev/ttyS2
+	//! -b <baud_rate>,   default : 115200
+	while ((ch = getopt(argc,argv,"d:b:")) != EOF){
+		switch(ch){
+			case 'b':
+				baudrate = strtoul(optarg, NULL, 10);
+				if(baudrate == 0)
+					printf("invalid baud rate '%s'",optarg);
+				break;
+			case 'd':
+				device_name = optarg;
+				debug_mode = true;
+				break;
+			default:
+				usage("invalid argument");
+		}
+	}
+
+	if(debug_mode){
+		printf("Opening debugging port for 3D visualization\n");
+		uart = open_uart(baudrate, device_name, &uart_config_original, &usb_uart);
+		if (uart < 0)
+                	printf("could not open %s", device_name);
+		else
+			printf("Open port success\n");
+	}
+
+	// print text
+	printf("Nonlinear SO3 Attitude Estimator initialized..\n\n");
+	fflush(stdout);
+
+	int overloadcounter = 19;
+
+	/* store start time to guard against too slow update rates */
+	uint64_t last_run = hrt_absolute_time();
+
+	struct sensor_combined_s raw;
+	memset(&raw, 0, sizeof(raw));
+
+	//! Initialize attitude vehicle uORB message.
+	struct vehicle_attitude_s att;
+	memset(&att, 0, sizeof(att));
+
+	struct vehicle_status_s state;
+	memset(&state, 0, sizeof(state));
+
+	uint64_t last_data = 0;
+	uint64_t last_measurement = 0;
+
+	/* subscribe to raw data */
+	int sub_raw = orb_subscribe(ORB_ID(sensor_combined));
+	/* rate-limit raw data updates to 200Hz */
+	orb_set_interval(sub_raw, 4);
+
+	/* subscribe to param changes */
+	int sub_params = orb_subscribe(ORB_ID(parameter_update));
+
+	/* subscribe to system state*/
+	int sub_state = orb_subscribe(ORB_ID(vehicle_status));
+
+	/* advertise attitude */
+	orb_advert_t pub_att = orb_advertise(ORB_ID(vehicle_attitude), &att);
+
+	int loopcounter = 0;
+	int printcounter = 0;
+
+	thread_running = true;
+
+	/* advertise debug value */
+	// struct debug_key_value_s dbg = { .key = "", .value = 0.0f };
+	// orb_advert_t pub_dbg = -1;
+
+	float sensor_update_hz[3] = {0.0f, 0.0f, 0.0f};
+	// XXX write this out to perf regs
+
+	/* keep track of sensor updates */
+	uint32_t sensor_last_count[3] = {0, 0, 0};
+	uint64_t sensor_last_timestamp[3] = {0, 0, 0};
+
+	struct attitude_estimator_so3_comp_params so3_comp_params;
+	struct attitude_estimator_so3_comp_param_handles so3_comp_param_handles;
+
+	/* initialize parameter handles */
+	parameters_init(&so3_comp_param_handles);
+
+	uint64_t start_time = hrt_absolute_time();
+	bool initialized = false;
+
+	float gyro_offsets[3] = { 0.0f, 0.0f, 0.0f };
+	unsigned offset_count = 0;
+
+	/* register the perf counter */
+	perf_counter_t so3_comp_loop_perf = perf_alloc(PC_ELAPSED, "attitude_estimator_so3_comp");
+
+	/* Main loop*/
+	while (!thread_should_exit) {
+
+		struct pollfd fds[2];
+		fds[0].fd = sub_raw;
+		fds[0].events = POLLIN;
+		fds[1].fd = sub_params;
+		fds[1].events = POLLIN;
+		int ret = poll(fds, 2, 1000);
+
+		if (ret < 0) {
+			/* XXX this is seriously bad - should be an emergency */
+		} else if (ret == 0) {
+			/* check if we're in HIL - not getting sensor data is fine then */
+			orb_copy(ORB_ID(vehicle_status), sub_state, &state);
+
+			if (!state.flag_hil_enabled) {
+				fprintf(stderr,
+					"[att so3_comp] WARNING: Not getting sensors - sensor app running?\n");
+			}
+
+		} else {
+
+			/* only update parameters if they changed */
+			if (fds[1].revents & POLLIN) {
+				/* read from param to clear updated flag */
+				struct parameter_update_s update;
+				orb_copy(ORB_ID(parameter_update), sub_params, &update);
+
+				/* update parameters */
+				parameters_update(&so3_comp_param_handles, &so3_comp_params);
+			}
+
+			/* only run filter if sensor values changed */
+			if (fds[0].revents & POLLIN) {
+
+				/* get latest measurements */
+				orb_copy(ORB_ID(sensor_combined), sub_raw, &raw);
+
+				if (!initialized) {
+
+					gyro_offsets[0] += raw.gyro_rad_s[0];
+					gyro_offsets[1] += raw.gyro_rad_s[1];
+					gyro_offsets[2] += raw.gyro_rad_s[2];
+					offset_count++;
+
+					if (hrt_absolute_time() - start_time > 3000000LL) {
+						initialized = true;
+						gyro_offsets[0] /= offset_count;
+						gyro_offsets[1] /= offset_count;
+						gyro_offsets[2] /= offset_count;
+					}
+
+				} else {
+
+					perf_begin(so3_comp_loop_perf);
+
+					/* Calculate data time difference in seconds */
+					dt = (raw.timestamp - last_measurement) / 1000000.0f;
+					last_measurement = raw.timestamp;
+					uint8_t update_vect[3] = {0, 0, 0};
+
+					/* Fill in gyro measurements */
+					if (sensor_last_count[0] != raw.gyro_counter) {
+						update_vect[0] = 1;
+						sensor_last_count[0] = raw.gyro_counter;
+						sensor_update_hz[0] = 1e6f / (raw.timestamp - sensor_last_timestamp[0]);
+						sensor_last_timestamp[0] = raw.timestamp;
+					}
+
+					gyro[0] =  raw.gyro_rad_s[0] - gyro_offsets[0];
+					gyro[1] =  raw.gyro_rad_s[1] - gyro_offsets[1];
+					gyro[2] =  raw.gyro_rad_s[2] - gyro_offsets[2];
+
+					/* update accelerometer measurements */
+					if (sensor_last_count[1] != raw.accelerometer_counter) {
+						update_vect[1] = 1;
+						sensor_last_count[1] = raw.accelerometer_counter;
+						sensor_update_hz[1] = 1e6f / (raw.timestamp - sensor_last_timestamp[1]);
+						sensor_last_timestamp[1] = raw.timestamp;
+					}
+
+					acc[0] = raw.accelerometer_m_s2[0];
+					acc[1] = raw.accelerometer_m_s2[1];
+					acc[2] = raw.accelerometer_m_s2[2];
+
+					/* update magnetometer measurements */
+					if (sensor_last_count[2] != raw.magnetometer_counter) {
+						update_vect[2] = 1;
+						sensor_last_count[2] = raw.magnetometer_counter;
+						sensor_update_hz[2] = 1e6f / (raw.timestamp - sensor_last_timestamp[2]);
+						sensor_last_timestamp[2] = raw.timestamp;
+					}
+
+					mag[0] = raw.magnetometer_ga[0];
+					mag[1] = raw.magnetometer_ga[1];
+					mag[2] = raw.magnetometer_ga[2];
+
+					uint64_t now = hrt_absolute_time();
+					unsigned int time_elapsed = now - last_run;
+					last_run = now;
+
+					if (time_elapsed > loop_interval_alarm) {
+						//TODO: add warning, cpu overload here
+						// if (overloadcounter == 20) {
+						// 	printf("CPU OVERLOAD DETECTED IN ATTITUDE ESTIMATOR EKF (%lu > %lu)\n", time_elapsed, loop_interval_alarm);
+						// 	overloadcounter = 0;
+						// }
+
+						overloadcounter++;
+					}
+
+					static bool const_initialized = false;
+
+					/* initialize with good values once we have a reasonable dt estimate */
+					if (!const_initialized && dt < 0.05f && dt > 0.005f) {
+						dt = 0.005f;
+						parameters_update(&so3_comp_param_handles, &so3_comp_params);
+						const_initialized = true;
+					}
+
+					/* do not execute the filter if not initialized */
+					if (!const_initialized) {
+						continue;
+					}
+
+					uint64_t timing_start = hrt_absolute_time();
+
+					// NOTE : Accelerometer is reversed.
+					// Because proper mount of PX4 will give you a reversed accelerometer readings.
+					NonlinearSO3AHRSupdate(gyro[0],gyro[1],gyro[2],-acc[0],-acc[1],-acc[2],mag[0],mag[1],mag[2],so3_comp_params.Kp,so3_comp_params.Ki, dt);
+
+					// Convert q->R.
+					Rot_matrix[0] = q0q0 + q1q1 - q2q2 - q3q3;// 11
+        				Rot_matrix[1] = 2.0 * (q1*q2 + q0*q3);	// 12
+        				Rot_matrix[2] = 2.0 * (q1*q3 - q0*q2);	// 13
+        				Rot_matrix[3] = 2.0 * (q1*q2 - q0*q3);	// 21
+        				Rot_matrix[4] = q0q0 - q1q1 + q2q2 - q3q3;// 22
+        				Rot_matrix[5] = 2.0 * (q2*q3 + q0*q1);	// 23
+        				Rot_matrix[6] = 2.0 * (q1*q3 + q0*q2);	// 31
+        				Rot_matrix[7] = 2.0 * (q2*q3 - q0*q1);	// 32
+        				Rot_matrix[8] = q0q0 - q1q1 - q2q2 + q3q3;// 33
+
+					//1-2-3 Representation.
+					//Equation (290) 
+					//Representing Attitude: Euler Angles, Unit Quaternions, and Rotation Vectors, James Diebel.
+					// Existing PX4 EKF code was generated by MATLAB which uses coloum major order matrix.
+					euler[0] = atan2f(Rot_matrix[5], Rot_matrix[8]);	//! Roll
+					euler[1] = -asinf(Rot_matrix[2]);	//! Pitch
+					euler[2] = atan2f(Rot_matrix[1],Rot_matrix[0]);		//! Yaw
+					
+					/* swap values for next iteration, check for fatal inputs */
+					if (isfinite(euler[0]) && isfinite(euler[1]) && isfinite(euler[2])) {
+						/* Do something */
+					} else {
+						/* due to inputs or numerical failure the output is invalid, skip it */
+						continue;
+					}
+
+					if (last_data > 0 && raw.timestamp - last_data > 12000) printf("[attitude estimator so3_comp] sensor data missed! (%llu)\n", raw.timestamp - last_data);
+
+					last_data = raw.timestamp;
+
+					/* send out */
+					att.timestamp = raw.timestamp;
+
+					// XXX Apply the same transformation to the rotation matrix
+					att.roll = euler[0] - so3_comp_params.roll_off;
+					att.pitch = euler[1] - so3_comp_params.pitch_off;
+					att.yaw = euler[2] - so3_comp_params.yaw_off;
+
+					//! Euler angle rate. But it needs to be investigated again.
+					/*
+					att.rollspeed = 2.0f*(-q1*dq0 + q0*dq1 - q3*dq2 + q2*dq3);
+					att.pitchspeed = 2.0f*(-q2*dq0 + q3*dq1 + q0*dq2 - q1*dq3);
+					att.yawspeed = 2.0f*(-q3*dq0 -q2*dq1 + q1*dq2 + q0*dq3);
+					*/
+					att.rollspeed = gyro[0];
+					att.pitchspeed = gyro[1];
+					att.yawspeed = gyro[2];
+
+					att.rollacc = 0;
+					att.pitchacc = 0;
+					att.yawacc = 0;
+
+					//! Quaternion
+					att.q[0] = q0;
+					att.q[1] = q1;
+					att.q[2] = q2;
+					att.q[3] = q3;
+					att.q_valid = true;
+
+					/* TODO: Bias estimation required */
+					memcpy(&att.rate_offsets, &(gyro_bias), sizeof(att.rate_offsets));
+
+					/* copy rotation matrix */
+					memcpy(&att.R, Rot_matrix, sizeof(Rot_matrix));
+					att.R_valid = true;
+
+					if (isfinite(att.roll) && isfinite(att.pitch) && isfinite(att.yaw)) {
+						// Broadcast
+						orb_publish(ORB_ID(vehicle_attitude), pub_att, &att);
+
+					} else {
+						warnx("NaN in roll/pitch/yaw estimate!");
+					}
+
+					perf_end(so3_comp_loop_perf);
+
+					//! This will print out debug packet to visualization software
+					if(debug_mode)
+					{
+						float quat[4];
+						quat[0] = q0;
+						quat[1] = q1;
+						quat[2] = q2;
+						quat[3] = q3;
+						send_uart_float_arr(quat,4);
+						send_uart_byte('\n');
+					}
+				}
+			}
+		}
+
+		loopcounter++;
+	}// while
+
+	thread_running = false;
+
+	/* Reset the UART flags to original state */
+        if (!usb_uart)
+                tcsetattr(uart, TCSANOW, &uart_config_original);
+
+	return 0;
+}
diff --git a/src/modules/attitude_estimator_so3_comp/attitude_estimator_so3_comp_params.c b/src/modules/attitude_estimator_so3_comp/attitude_estimator_so3_comp_params.c
new file mode 100755
index 000000000..f962515df
--- /dev/null
+++ b/src/modules/attitude_estimator_so3_comp/attitude_estimator_so3_comp_params.c
@@ -0,0 +1,63 @@
+/*
+ * Author: Hyon Lim <limhyon@gmail.com, hyonlim@snu.ac.kr>
+ *
+ * @file attitude_estimator_so3_comp_params.c
+ *
+ * Implementation of nonlinear complementary filters on the SO(3).
+ * This code performs attitude estimation by using accelerometer, gyroscopes and magnetometer.
+ * Result is provided as quaternion, 1-2-3 Euler angle and rotation matrix.
+ * 
+ * Theory of nonlinear complementary filters on the SO(3) is based on [1].
+ * Quaternion realization of [1] is based on [2].
+ * Optmized quaternion update code is based on Sebastian Madgwick's implementation.
+ * 
+ * References
+ *  [1] Mahony, R.; Hamel, T.; Pflimlin, Jean-Michel, "Nonlinear Complementary Filters on the Special Orthogonal Group," Automatic Control, IEEE Transactions on , vol.53, no.5, pp.1203,1218, June 2008
+ *  [2] Euston, M.; Coote, P.; Mahony, R.; Jonghyuk Kim; Hamel, T., "A complementary filter for attitude estimation of a fixed-wing UAV," Intelligent Robots and Systems, 2008. IROS 2008. IEEE/RSJ International Conference on , vol., no., pp.340,345, 22-26 Sept. 2008
+ */
+
+#include "attitude_estimator_so3_comp_params.h"
+
+/* This is filter gain for nonlinear SO3 complementary filter */
+/* NOTE : How to tune the gain? First of all, stick with this default gain. And let the quad in stable place.
+   Log the steady state reponse of filter. If it is too slow, increase SO3_COMP_KP.
+   If you are flying from ground to high altitude in short amount of time, please increase SO3_COMP_KI which
+   will compensate gyro bias which depends on temperature and vibration of your vehicle */
+PARAM_DEFINE_FLOAT(SO3_COMP_KP, 1.0f); //! This parameter will give you about 15 seconds convergence time.
+                                       //! You can set this gain higher if you want more fast response.
+                                       //! But note that higher gain will give you also higher overshoot.
+PARAM_DEFINE_FLOAT(SO3_COMP_KI, 0.05f); //! This gain will incorporate slow time-varying bias (e.g., temperature change)
+					//! This gain is depend on your vehicle status.
+
+/* offsets in roll, pitch and yaw of sensor plane and body */
+PARAM_DEFINE_FLOAT(ATT_ROLL_OFFS, 0.0f);
+PARAM_DEFINE_FLOAT(ATT_PITCH_OFFS, 0.0f);
+PARAM_DEFINE_FLOAT(ATT_YAW_OFFS, 0.0f);
+
+int parameters_init(struct attitude_estimator_so3_comp_param_handles *h)
+{
+	/* Filter gain parameters */
+	h->Kp = 	param_find("SO3_COMP_KP");
+	h->Ki = 	param_find("SO3_COMP_KI");
+
+	/* Attitude offset (WARNING: Do not change if you do not know what exactly this variable wil lchange) */
+	h->roll_off  =	param_find("ATT_ROLL_OFFS");
+	h->pitch_off =	param_find("ATT_PITCH_OFFS");
+	h->yaw_off   =	param_find("ATT_YAW_OFFS");
+
+	return OK;
+}
+
+int parameters_update(const struct attitude_estimator_so3_comp_param_handles *h, struct attitude_estimator_so3_comp_params *p)
+{
+	/* Update filter gain */
+	param_get(h->Kp, &(p->Kp));
+	param_get(h->Ki, &(p->Ki));
+
+	/* Update attitude offset */
+	param_get(h->roll_off, &(p->roll_off));
+	param_get(h->pitch_off, &(p->pitch_off));
+	param_get(h->yaw_off, &(p->yaw_off));
+
+	return OK;
+}
diff --git a/src/modules/attitude_estimator_so3_comp/attitude_estimator_so3_comp_params.h b/src/modules/attitude_estimator_so3_comp/attitude_estimator_so3_comp_params.h
new file mode 100755
index 000000000..f00695630
--- /dev/null
+++ b/src/modules/attitude_estimator_so3_comp/attitude_estimator_so3_comp_params.h
@@ -0,0 +1,44 @@
+/*
+ * Author: Hyon Lim <limhyon@gmail.com, hyonlim@snu.ac.kr>
+ *
+ * @file attitude_estimator_so3_comp_params.h
+ *
+ * Implementation of nonlinear complementary filters on the SO(3).
+ * This code performs attitude estimation by using accelerometer, gyroscopes and magnetometer.
+ * Result is provided as quaternion, 1-2-3 Euler angle and rotation matrix.
+ * 
+ * Theory of nonlinear complementary filters on the SO(3) is based on [1].
+ * Quaternion realization of [1] is based on [2].
+ * Optmized quaternion update code is based on Sebastian Madgwick's implementation.
+ * 
+ * References
+ *  [1] Mahony, R.; Hamel, T.; Pflimlin, Jean-Michel, "Nonlinear Complementary Filters on the Special Orthogonal Group," Automatic Control, IEEE Transactions on , vol.53, no.5, pp.1203,1218, June 2008
+ *  [2] Euston, M.; Coote, P.; Mahony, R.; Jonghyuk Kim; Hamel, T., "A complementary filter for attitude estimation of a fixed-wing UAV," Intelligent Robots and Systems, 2008. IROS 2008. IEEE/RSJ International Conference on , vol., no., pp.340,345, 22-26 Sept. 2008
+ */
+
+#include <systemlib/param/param.h>
+
+struct attitude_estimator_so3_comp_params {
+	float Kp;
+	float Ki;
+	float roll_off;
+	float pitch_off;
+	float yaw_off;
+};
+
+struct attitude_estimator_so3_comp_param_handles {
+	param_t Kp, Ki;
+	param_t roll_off, pitch_off, yaw_off;
+};
+
+/**
+ * Initialize all parameter handles and values
+ *
+ */
+int parameters_init(struct attitude_estimator_so3_comp_param_handles *h);
+
+/**
+ * Update all parameters
+ *
+ */
+int parameters_update(const struct attitude_estimator_so3_comp_param_handles *h, struct attitude_estimator_so3_comp_params *p);
diff --git a/src/modules/attitude_estimator_so3_comp/module.mk b/src/modules/attitude_estimator_so3_comp/module.mk
new file mode 100644
index 000000000..92f43d920
--- /dev/null
+++ b/src/modules/attitude_estimator_so3_comp/module.mk
@@ -0,0 +1,8 @@
+#
+# Attitude estimator (Nonlinear SO3 complementary Filter)
+#
+
+MODULE_COMMAND	 = attitude_estimator_so3_comp
+
+SRCS		 = attitude_estimator_so3_comp_main.cpp \
+		   attitude_estimator_so3_comp_params.c
diff --git a/src/modules/fixedwing_backside/fixedwing_backside_main.cpp b/src/modules/fixedwing_backside/fixedwing_backside_main.cpp
index e21990c92..c3d57a85a 100644
--- a/src/modules/fixedwing_backside/fixedwing_backside_main.cpp
+++ b/src/modules/fixedwing_backside/fixedwing_backside_main.cpp
@@ -47,6 +47,7 @@
 #include <systemlib/systemlib.h>
 #include <controllib/fixedwing.hpp>
 #include <systemlib/param/param.h>
+#include <systemlib/err.h>
 #include <drivers/drv_hrt.h>
 #include <math.h>
 
@@ -80,7 +81,7 @@ usage(const char *reason)
 	if (reason)
 		fprintf(stderr, "%s\n", reason);
 
-	fprintf(stderr, "usage: control_demo {start|stop|status} [-p <additional params>]\n\n");
+	fprintf(stderr, "usage: fixedwing_backside {start|stop|status} [-p <additional params>]\n\n");
 	exit(1);
 }
 
@@ -101,13 +102,13 @@ int fixedwing_backside_main(int argc, char *argv[])
 	if (!strcmp(argv[1], "start")) {
 
 		if (thread_running) {
-			printf("control_demo already running\n");
+			warnx("already running");
 			/* this is not an error */
 			exit(0);
 		}
 
 		thread_should_exit = false;
-		deamon_task = task_spawn("control_demo",
+		deamon_task = task_spawn("fixedwing_backside",
 					 SCHED_DEFAULT,
 					 SCHED_PRIORITY_MAX - 10,
 					 5120,
@@ -128,10 +129,10 @@ int fixedwing_backside_main(int argc, char *argv[])
 
 	if (!strcmp(argv[1], "status")) {
 		if (thread_running) {
-			printf("\tcontrol_demo app is running\n");
+			warnx("is running");
 
 		} else {
-			printf("\tcontrol_demo app not started\n");
+			warnx("not started");
 		}
 
 		exit(0);
@@ -144,7 +145,7 @@ int fixedwing_backside_main(int argc, char *argv[])
 int control_demo_thread_main(int argc, char *argv[])
 {
 
-	printf("[control_Demo] starting\n");
+	warnx("starting");
 
 	using namespace control;
 
@@ -156,7 +157,7 @@ int control_demo_thread_main(int argc, char *argv[])
 		autopilot.update();
 	}
 
-	printf("[control_demo] exiting.\n");
+	warnx("exiting.");
 
 	thread_running = false;
 
@@ -165,6 +166,6 @@ int control_demo_thread_main(int argc, char *argv[])
 
 void test()
 {
-	printf("beginning control lib test\n");
+	warnx("beginning control lib test");
 	control::basicBlocksTest();
 }
diff --git a/src/modules/gpio_led/gpio_led.c b/src/modules/gpio_led/gpio_led.c
index a80bf9cb8..43cbe74c7 100644
--- a/src/modules/gpio_led/gpio_led.c
+++ b/src/modules/gpio_led/gpio_led.c
@@ -48,6 +48,7 @@
 #include <nuttx/wqueue.h>
 #include <nuttx/clock.h>
 #include <systemlib/systemlib.h>
+#include <systemlib/err.h>
 #include <uORB/uORB.h>
 #include <uORB/topics/vehicle_status.h>
 #include <poll.h>
@@ -64,6 +65,7 @@ struct gpio_led_s {
 };
 
 static struct gpio_led_s gpio_led_data;
+static bool gpio_led_started = false;
 
 __EXPORT int gpio_led_main(int argc, char *argv[]);
 
@@ -75,31 +77,54 @@ int gpio_led_main(int argc, char *argv[])
 {
 	int pin = GPIO_EXT_1;
 
-	if (argc > 1) {
-		if (!strcmp(argv[1], "-p")) {
-			if (!strcmp(argv[2], "1")) {
-				pin = GPIO_EXT_1;
+	if (argc < 2) {
+		errx(1, "no argument provided. Try 'start' or 'stop' [-p 1/2]");
 
-			} else if (!strcmp(argv[2], "2")) {
-				pin = GPIO_EXT_2;
+	} else {
 
-			} else {
-				printf("[gpio_led] Unsupported pin: %s\n", argv[2]);
+		/* START COMMAND HANDLING */
+		if (!strcmp(argv[1], "start")) {
+
+			if (argc > 2) {
+				if (!strcmp(argv[1], "-p")) {
+					if (!strcmp(argv[2], "1")) {
+						pin = GPIO_EXT_1;
+
+					} else if (!strcmp(argv[2], "2")) {
+						pin = GPIO_EXT_2;
+
+					} else {
+						warnx("[gpio_led] Unsupported pin: %s\n", argv[2]);
+						exit(1);
+					}
+				}
+			}
+
+			memset(&gpio_led_data, 0, sizeof(gpio_led_data));
+			gpio_led_data.pin = pin;
+			int ret = work_queue(LPWORK, &gpio_led_data.work, gpio_led_start, &gpio_led_data, 0);
+
+			if (ret != 0) {
+				warnx("[gpio_led] Failed to queue work: %d\n", ret);
 				exit(1);
+
+			} else {
+				gpio_led_started = true;
 			}
-		}
-	}
 
-	memset(&gpio_led_data, 0, sizeof(gpio_led_data));
-	gpio_led_data.pin = pin;
-	int ret = work_queue(LPWORK, &gpio_led_data.work, gpio_led_start, &gpio_led_data, 0);
+			exit(0);
 
-	if (ret != 0) {
-		printf("[gpio_led] Failed to queue work: %d\n", ret);
-		exit(1);
-	}
+			/* STOP COMMAND HANDLING */
+
+		} else if (!strcmp(argv[1], "stop")) {
+			gpio_led_started = false;
 
-	exit(0);
+			/* INVALID COMMAND */
+
+		} else {
+			errx(1, "unrecognized command '%s', only supporting 'start' or 'stop'", argv[1]);
+		}
+	}
 }
 
 void gpio_led_start(FAR void *arg)
@@ -110,7 +135,7 @@ void gpio_led_start(FAR void *arg)
 	priv->gpio_fd = open(GPIO_DEVICE_PATH, 0);
 
 	if (priv->gpio_fd < 0) {
-		printf("[gpio_led] GPIO: open fail\n");
+		warnx("[gpio_led] GPIO: open fail\n");
 		return;
 	}
 
@@ -125,11 +150,11 @@ void gpio_led_start(FAR void *arg)
 	int ret = work_queue(LPWORK, &priv->work, gpio_led_cycle, priv, 0);
 
 	if (ret != 0) {
-		printf("[gpio_led] Failed to queue work: %d\n", ret);
+		warnx("[gpio_led] Failed to queue work: %d\n", ret);
 		return;
 	}
 
-	printf("[gpio_led] Started, using pin GPIO_EXT%i\n", priv->pin);
+	warnx("[gpio_led] Started, using pin GPIO_EXT%i\n", priv->pin);
 }
 
 void gpio_led_cycle(FAR void *arg)
@@ -187,5 +212,6 @@ void gpio_led_cycle(FAR void *arg)
 		priv->counter = 0;
 
 	/* repeat cycle at 5 Hz*/
-	work_queue(LPWORK, &priv->work, gpio_led_cycle, priv, USEC2TICK(200000));
+	if (gpio_led_started)
+		work_queue(LPWORK, &priv->work, gpio_led_cycle, priv, USEC2TICK(200000));
 }
diff --git a/src/modules/px4iofirmware/mixer.cpp b/src/modules/px4iofirmware/mixer.cpp
index 0b8ed6dc5..a2193b526 100644
--- a/src/modules/px4iofirmware/mixer.cpp
+++ b/src/modules/px4iofirmware/mixer.cpp
@@ -294,8 +294,7 @@ mixer_handle_text(const void *buffer, size_t length)
 	case F2I_MIXER_ACTION_APPEND:
 		isr_debug(2, "append %d", length);
 
-		/* check for overflow - this is really fatal */
-		/* XXX could add just what will fit & try to parse, then repeat... */
+		/* check for overflow - this would be really fatal */
 		if ((mixer_text_length + text_length + 1) > sizeof(mixer_text)) {
 			r_status_flags &= ~PX4IO_P_STATUS_FLAGS_MIXER_OK;
 			return;
@@ -314,8 +313,13 @@ mixer_handle_text(const void *buffer, size_t length)
 		/* if anything was parsed */
 		if (resid != mixer_text_length) {
 
-			/* ideally, this should test resid == 0 ? */
-			r_status_flags |= PX4IO_P_STATUS_FLAGS_MIXER_OK;
+			/* only set mixer ok if no residual is left over */
+			if (resid == 0) {
+				r_status_flags |= PX4IO_P_STATUS_FLAGS_MIXER_OK;
+			} else {
+				/* not yet reached the end of the mixer, set as not ok */
+				r_status_flags &= ~PX4IO_P_STATUS_FLAGS_MIXER_OK;
+			}
 
 			isr_debug(2, "used %u", mixer_text_length - resid);
 
@@ -338,11 +342,13 @@ mixer_set_failsafe()
 {
 	/* 
 	 * Check if a custom failsafe value has been written,
-	 * else use the opportunity to set decent defaults.
+	 * or if the mixer is not ok and bail out.
 	 */
-	if (r_setup_arming & PX4IO_P_SETUP_ARMING_FAILSAFE_CUSTOM)
+	if ((r_setup_arming & PX4IO_P_SETUP_ARMING_FAILSAFE_CUSTOM) ||
+		!(r_status_flags & PX4IO_P_STATUS_FLAGS_MIXER_OK))
 		return;
 
+	/* set failsafe defaults to the values for all inputs = 0 */
 	float	outputs[IO_SERVO_COUNT];
 	unsigned mixed;
 
diff --git a/src/systemcmds/mixer/mixer.c b/src/systemcmds/mixer/mixer.c
index 55c4f0836..e642ed067 100644
--- a/src/systemcmds/mixer/mixer.c
+++ b/src/systemcmds/mixer/mixer.c
@@ -88,8 +88,8 @@ load(const char *devname, const char *fname)
 {
 	int		dev;
 	FILE		*fp;
-	char		line[80];
-	char		buf[512];
+	char		line[120];
+	char		buf[2048];
 
 	/* open the device */
 	if ((dev = open(devname, 0)) < 0)