Merged with newer, cleaned up code, fixed the checksum error

apps/drivers/drv_gps.h

@@ -54,8 +54,6 @@ typedef enum {
 } gps_driver_mode_t;
 
 
-
-
 /*
  * ObjDev tag for GPS data.
  */

apps/drivers/gps/gps.cpp

@@ -33,7 +33,7 @@
 
 /**
  * @file gps.cpp
- * Driver for the GPS on UART6
+ * Driver for the GPS on a serial port
  */
 
 #include <nuttx/config.h>
@@ -107,46 +107,41 @@ public:
 
 private:
 
-	int				_task_should_exit;
-	int				_serial_fd;					///< serial interface to GPS
-	unsigned			_baudrate;
-	unsigned			_baudrates_to_try[NUMBER_OF_BAUDRATES];
-	uint8_t				_send_buffer[SEND_BUFFER_LENGTH];
-	perf_counter_t			_sample_perf;
-	perf_counter_t			_comms_errors;
-	perf_counter_t			_buffer_overflows;
-	volatile int			_task;						///< worker task
+	bool				_task_should_exit;						///< flag to make the main worker task exit
+	int					_serial_fd;								///< serial interface to GPS
+	unsigned			_baudrate;								///< current baudrate
+	unsigned			_baudrates_to_try[NUMBER_OF_BAUDRATES]; ///< try different baudrates that GPS could be set to
+	volatile int		_task;									///< worker task
+	bool				_config_needed;							///< flag to signal that configuration of GPS is needed
+	bool 				_baudrate_changed;						///< flag to signal that the baudrate with the GPS has changed
+	bool				_mode_changed;							///< flag that the GPS mode has changed
+	gps_driver_mode_t	_mode;									///< current mode
+	GPS_Helper			*_Helper;								///< Class for either UBX, MTK or NMEA helper
+	struct vehicle_gps_position_s _report;						///< uORB topic for gps position
+	orb_advert_t		_report_pub;							///< uORB pub for gps position
+	float				_rate;									///< position update rate
 
-	bool				_response_received;
-	bool				_config_needed;
-	bool 				_baudrate_changed;
-	bool				_mode_changed;
-	bool				_healthy;
-	gps_driver_mode_t		_mode;
-	unsigned 			_messages_received;
-	float				_rate;						///< position update rate
-
-	GPS_Helper			*_Helper;					///< class for either UBX, MTK or NMEA helper
-
-	struct vehicle_gps_position_s	_report;					///< the current GPS report
-	orb_advert_t			_report_pub;					///< the publication topic, only valid on first valid GPS module message
-
-	void				recv();
 
+	/**
+	 * Try to configure the GPS, handle outgoing communication to the GPS
+	 */
 	void				config();
 
+	/**
+	 * Trampoline to the worker task
+	 */
 	static void			task_main_trampoline(void *arg);
 
 
 	/**
-	 * Worker task.
+	 * Worker task: main GPS thread that configures the GPS and parses incoming data, always running
 	 */
 	void				task_main(void);
 
 	/**
-	 * Set the module baud rate
+	 * Set the baudrate of the UART to the GPS
 	 */
-	int				set_baudrate(unsigned baud);
+	int					set_baudrate(unsigned baud);
 
 	/**
 	 * Send a reset command to the GPS
@@ -176,12 +171,10 @@ GPS::GPS() :
 	_config_needed(true),
 	_baudrate_changed(false),
 	_mode_changed(true),
-	_healthy(false),
 	_mode(GPS_DRIVER_MODE_UBX),
-	_messages_received(0),
 	_Helper(nullptr),
-	_rate(0.0f),
-	_report_pub(-1)
+	_report_pub(-1),
+	_rate(0.0f)
 {
 	/* we need this potentially before it could be set in task_main */
 	g_dev = this;
@@ -216,7 +209,7 @@ GPS::init()
 	if (CDev::init() != OK)
 		goto out;
 
-	/* start the IO interface task */
+	/* start the GPS driver worker task */
 	_task = task_create("gps", SCHED_PRIORITY_SLOW_DRIVER, 2048, (main_t)&GPS::task_main_trampoline, nullptr);
 
 	if (_task < 0) {
@@ -275,17 +268,22 @@ void
 GPS::config()
 {
 	int length = 0;
+	uint8_t	send_buffer[SEND_BUFFER_LENGTH];
 
-	_Helper->configure(_config_needed, _baudrate_changed, _baudrate, _send_buffer, length, SEND_BUFFER_LENGTH);
+	_Helper->configure(_config_needed, _baudrate_changed, _baudrate, send_buffer, length, SEND_BUFFER_LENGTH);
 
-	/* the message needs to be sent at the old baudrate */
+	/* The config message is sent sent at the old baudrate */
 	if (length > 0) {
-		if (length != ::write(_serial_fd, _send_buffer, length)) {
+
+		if (length != ::write(_serial_fd, send_buffer, length)) {
 			debug("write config failed");
 			return;
 		}
 	}
 
+	/* Sometimes the baudrate needs to be changed, for instance UBX with factory settings are changed
+	 * from 9600 to 38400
+	 */
 	if (_baudrate_changed) {
 		set_baudrate(_baudrate);
 		_baudrate_changed = false;
@@ -304,11 +302,10 @@ GPS::task_main()
 	log("starting");
 
 	/* open the serial port */
-	_serial_fd = ::open("/dev/ttyS3", O_RDWR);
+	_serial_fd = ::open("/dev/ttyS3", O_RDWR); //TODO make the device dynamic depending on startup parameters
 
-	uint8_t buf[256];
-	int baud_i = 0;
-	uint64_t time_before_configuration;
+	/* buffer to read from the serial port */
+	uint8_t buf[32];
 
 	if (_serial_fd < 0) {
 		log("failed to open serial port: %d", errno);
@@ -326,16 +323,16 @@ GPS::task_main()
 	/* lock against the ioctl handler */
 	lock();
 
-
+	unsigned baud_i = 0;
 	_baudrate = _baudrates_to_try[baud_i];
 	set_baudrate(_baudrate);
 
-	time_before_configuration = hrt_absolute_time();
+	uint64_t time_before_configuration = hrt_absolute_time();
 
 	uint64_t last_rate_measurement = hrt_absolute_time();
 	unsigned last_rate_count = 0;
 
-	/* loop handling received serial bytes */
+	/* loop handling received serial bytes and also configuring in between */
 	while (!_task_should_exit) {
 
 		if (_mode_changed) {
@@ -364,14 +361,17 @@ GPS::task_main()
 			_mode_changed = false;
 		}
 
+		/* If a configuration does not finish in the config timeout, change the baudrate */
 		if (_config_needed && time_before_configuration + CONFIG_TIMEOUT < hrt_absolute_time()) {
 			baud_i = (baud_i+1)%NUMBER_OF_BAUDRATES;
 			_baudrate = _baudrates_to_try[baud_i];
 			set_baudrate(_baudrate);
+			_Helper->reset();
 			time_before_configuration = hrt_absolute_time();
 		}
 
-
+		/* during configuration, the timeout should be small, so that we can send config messages in between parsing,
+		 * but during normal operation, it should never timeout because updates should arrive with 5Hz */
 		int poll_timeout;
 		if (_config_needed) {
 			poll_timeout = 50;
@@ -409,11 +409,21 @@ GPS::task_main()
 
 				/* pass received bytes to the packet decoder */
 				int j;
+				int ret_parse = 0;
 				for (j = 0; j < count; j++) {
-					_messages_received += _Helper->parse(buf[j], &_report);
+					ret_parse += _Helper->parse(buf[j], &_report);
 				}
-				if (_messages_received > 0) {
-					if (_config_needed == true) {
+
+				if (ret_parse < 0) {
+					/* This means something went wrong in the parser, let's reconfigure */
+					if (!_config_needed) {
+						_config_needed = true;
+						debug("Lost GPS module");
+					}
+					config();
+				} else if (ret_parse > 0) {
+					/* Looks like we got a valid position update, stop configuring and publish it */
+					if (_config_needed) {
 						_config_needed = false;
 						debug("Found GPS module");
 					}
@@ -424,8 +434,6 @@ GPS::task_main()
 					} else {
 						_report_pub = orb_advertise(ORB_ID(vehicle_gps_position), &_report);
 					}
-
-					_messages_received = 0;
 					last_rate_count++;
 
 					/* measure update rate every 5 seconds */
@@ -435,10 +443,10 @@ GPS::task_main()
 						last_rate_count = 0;
 					}
 				}
+				/* else if ret_parse == 0: just keep parsing */
 			}
 		}
 	}
-out:
 	debug("exiting");
 
 	::close(_serial_fd);
@@ -469,7 +477,6 @@ GPS::set_baudrate(unsigned baud)
 		warnx("ERROR: Unsupported baudrate: %d\n", baud);
 		return -EINVAL;
 	}
-
 	struct termios uart_config;
 	int termios_state;
 
@@ -482,24 +489,26 @@ GPS::set_baudrate(unsigned baud)
 	uart_config.c_cflag &= ~(CSTOPB | PARENB);
 
 	/* set baud rate */
-	if (cfsetispeed(&uart_config, speed) < 0 || cfsetospeed(&uart_config, speed) < 0) {
-		warnx("ERROR setting config: %d (cfsetispeed, cfsetospeed)\n", termios_state);
+	if ((termios_state = cfsetispeed(&uart_config, speed)) < 0) {
+		warnx("ERROR setting config: %d (cfsetispeed)\n", termios_state);
+		return -1;
+	}
+	if ((termios_state = cfsetospeed(&uart_config, speed)) < 0) {
+		warnx("ERROR setting config: %d (cfsetospeed)\n", termios_state);
 		return -1;
 	}
-
-
 	if ((termios_state = tcsetattr(_serial_fd, TCSANOW, &uart_config)) < 0) {
 		warnx("ERROR setting baudrate (tcsetattr)\n");
 		return -1;
 	}
-
 	/* XXX if resetting the parser here, ensure it does exist (check for null pointer) */
+	return 0;
 }
 
 void
 GPS::cmd_reset()
 {
-	_healthy = false;
+	_config_needed = true;
 }
 
 void
@@ -524,10 +533,12 @@ GPS::print_info()
 	warnx("baudrate: %d, status: %s", _baudrate, (_config_needed) ? "NOT OK" : "OK");
 	if (_report.timestamp != 0) {
 		warnx("position lock: %dD, last update %4.2f seconds ago", (int)_report.fix_type,
-			((float)(hrt_absolute_time() - _report.timestamp) / 1000000.0f));
+			(double)((float)(hrt_absolute_time() - _report.timestamp) / 1000000.0f));
 		warnx("lat: %d, lon: %d, alt: %d", _report.lat, _report.lon, _report.alt);
 		warnx("update rate: %6.2f Hz", (double)_rate);
 	}
+
+	usleep(100000);
 }
 
 /**
@@ -583,6 +594,9 @@ fail:
 	errx(1, "driver start failed");
 }
 
+/**
+ * Stop the driver.
+ */
 void
 stop()
 {

apps/drivers/gps/gps_helper.h

@@ -40,8 +40,9 @@
 class GPS_Helper
 {
 public:
-	virtual void			configure(bool&, bool&, unsigned&, uint8_t*, int&, const unsigned) = 0;
-	virtual int 			parse(uint8_t, struct vehicle_gps_position_s*) = 0;
+	virtual void			reset() = 0;
+	virtual void			configure(bool &config_needed, bool &baudrate_changed, unsigned &baudrate, uint8_t *buffer, int &length, const unsigned max_length) = 0;
+	virtual int 			parse(uint8_t b, struct vehicle_gps_position_s *gps_position) = 0;
 };
 
 #endif /* GPS_HELPER_H */

apps/drivers/gps/ubx.cpp

@@ -48,36 +48,41 @@
 
 
 UBX::UBX() :
-_waited(0),
 _config_state(UBX_CONFIG_STATE_PRT),
+_waiting_for_ack(false),
 _new_nav_posllh(false),
 _new_nav_timeutc(false),
 _new_nav_dop(false),
 _new_nav_sol(false),
 _new_nav_velned(false)
 {
-	decodeInit();
-	_waiting_for_ack = false;
+	reset();
 }
 
 UBX::~UBX()
 {
 }
 
+void
+UBX::reset()
+{
+	decodeInit();
+	_config_state = UBX_CONFIG_STATE_PRT;
+	_waiting_for_ack = false;
+}
+
 void
 UBX::configure(bool &config_needed, bool &baudrate_changed, unsigned &baudrate, uint8_t *buffer, int &length, const unsigned max_length)
 {
-	/* make sure the buffer to write the message is long enough */
+	/* make sure the buffer, where the message is written to, is long enough */
 	assert(sizeof(type_gps_bin_cfg_prt_packet_t)+2 <= max_length);
 
-	/* try again after 10 times */
-	if (_waited > 10) {
-		_waiting_for_ack = false;
-	}
-
+	/* Only send a new config message when we got the ACK of the last one,
+	 * otherwise we might not configure all the messages because the ACK comes from an older/previos CFD command
+	 * reason being that the ACK only includes CFG-MSG but not to which NAV MSG it belongs.
+	 */
 	if (!_waiting_for_ack) {
 		_waiting_for_ack = true;
-		_waited = 0;
 		if (_config_state == UBX_CONFIG_STATE_CONFIGURED) {
 			config_needed = false;
 			length = 0;
@@ -85,10 +90,15 @@ UBX::configure(bool &config_needed, bool &baudrate_changed, unsigned &baudrate,
 			_waiting_for_ack = false;
 			return;
 		} else if (_config_state == UBX_CONFIG_STATE_PRT) {
-			/* send a CFT-PRT message to define set ubx protocol and leave the baudrate as is, we just want an ACK-ACK from this */
+
+			/* Send a CFG-PRT message to set the UBX protocol for in and out
+			 * and leave the baudrate as it is, we just want an ACK-ACK from this
+			 */
 			type_gps_bin_cfg_prt_packet_t cfg_prt_packet;
+			/* Set everything else of the packet to 0, otherwise the module wont accept it */
 			memset(&cfg_prt_packet, 0, sizeof(cfg_prt_packet));
 
+			/* Define the package contents, don't change the baudrate */
 			cfg_prt_packet.clsID		= UBX_CLASS_CFG;
 			cfg_prt_packet.msgID		= UBX_MESSAGE_CFG_PRT;
 			cfg_prt_packet.length		= UBX_CFG_PRT_LENGTH;
@@ -98,18 +108,20 @@ UBX::configure(bool &config_needed, bool &baudrate_changed, unsigned &baudrate,
 			cfg_prt_packet.inProtoMask	= UBX_CFG_PRT_PAYLOAD_INPROTOMASK;
 			cfg_prt_packet.outProtoMask	= UBX_CFG_PRT_PAYLOAD_OUTPROTOMASK;
 
+			/* Calculate the checksum now */
 			addChecksumToMessage((uint8_t*)&cfg_prt_packet, sizeof(cfg_prt_packet));
 
+			/* Start with the two sync bytes */
 			buffer[0] = UBX_SYNC1;
 			buffer[1] = UBX_SYNC2;
+			/* Copy it to the buffer that will be written back in the main gps driver */
 			memcpy(&(buffer[2]), &cfg_prt_packet, sizeof(cfg_prt_packet));
+			/* Set the length of the packet (plus the 2 sync bytes) */
 			length = sizeof(cfg_prt_packet)+2;
 
 		} else if (_config_state == UBX_CONFIG_STATE_PRT_NEW_BAUDRATE) {
 
-//			printf("Send change of baudrate now\n");
-
-			/* send a CFT-PRT message to define set ubx protocol and and baudrate, now let's try to switch the baudrate */
+			/* Send a CFG-PRT message again, this time change the baudrate */
 			type_gps_bin_cfg_prt_packet_t cfg_prt_packet;
 			memset(&cfg_prt_packet, 0, sizeof(cfg_prt_packet));
 
@@ -129,18 +141,15 @@ UBX::configure(bool &config_needed, bool &baudrate_changed, unsigned &baudrate,
 			memcpy(&(buffer[2]), &cfg_prt_packet, sizeof(cfg_prt_packet));
 			length = sizeof(cfg_prt_packet)+2;
 
-			/* detection when the baudrate has been changed in the first step */
+			/* If the new baudrate will be different from the current one, we should report that back to the driver */
 			if (UBX_CFG_PRT_PAYLOAD_BAUDRATE != baudrate) {
-				/* set a flag and exit */
 				baudrate=UBX_CFG_PRT_PAYLOAD_BAUDRATE;
 				baudrate_changed = true;
-				_config_state = UBX_CONFIG_STATE_RATE;
-				_waiting_for_ack = false;
-				return;
+				/* Don't wait for an ACK, we're switching baudrate and we might never get,
+				 * after that, start fresh */
+				reset();
 			}
 
-
-
 		} else if (_config_state == UBX_CONFIG_STATE_RATE) {
 
 			/* send a CFT-RATE message to define update rate */
@@ -162,9 +171,9 @@ UBX::configure(bool &config_needed, bool &baudrate_changed, unsigned &baudrate,
 			length = sizeof(cfg_rate_packet)+2;
 
 		} else if (_config_state == UBX_CONFIG_STATE_NAV5) {
-			/* send a NAV5 message to set the options for the internal estimator */
+			/* send a NAV5 message to set the options for the internal filter */
 			type_gps_bin_cfg_nav5_packet_t cfg_nav5_packet;
-			memset(&cfg_nav5_packet, 0, sizeof(cfg_nav5_packet)); //set everything to 0
+			memset(&cfg_nav5_packet, 0, sizeof(cfg_nav5_packet));
 
 			cfg_nav5_packet.clsID        = UBX_CLASS_CFG;
 			cfg_nav5_packet.msgID        = UBX_MESSAGE_CFG_NAV5;
@@ -181,15 +190,16 @@ UBX::configure(bool &config_needed, bool &baudrate_changed, unsigned &baudrate,
 			length = sizeof(cfg_nav5_packet)+2;
 
 		} else {
-			/* catch the remaining config states here */
+			/* Catch the remaining config states here, they all need the same packet type */
 
 			type_gps_bin_cfg_msg_packet_t cfg_msg_packet;
-			memset(&cfg_msg_packet, 0, sizeof(cfg_msg_packet)); //set everything to 0
+			memset(&cfg_msg_packet, 0, sizeof(cfg_msg_packet));
 
 			cfg_msg_packet.clsID        = UBX_CLASS_CFG;
 			cfg_msg_packet.msgID        = UBX_MESSAGE_CFG_MSG;
 			cfg_msg_packet.length       = UBX_CFG_MSG_LENGTH;
-			cfg_msg_packet.rate[1]      = UBX_CFG_MSG_PAYLOAD_RATE1;
+			/* Choose fast 5Hz rate for all messages except SVINFO which is big and not important */
+			cfg_msg_packet.rate[1]      = UBX_CFG_MSG_PAYLOAD_RATE1_5HZ;
 
 			switch (_config_state) {
 				case UBX_CONFIG_STATE_MSG_NAV_POSLLH:
@@ -207,7 +217,8 @@ UBX::configure(bool &config_needed, bool &baudrate_changed, unsigned &baudrate,
 				case UBX_CONFIG_STATE_MSG_NAV_SVINFO:
 					cfg_msg_packet.msgClass_payload = UBX_CLASS_NAV;
 					cfg_msg_packet.msgID_payload = UBX_MESSAGE_NAV_SVINFO;
-					cfg_msg_packet.rate[1] = 5;
+					/* For satelites info 1Hz is enough */
+					cfg_msg_packet.rate[1] = UBX_CFG_MSG_PAYLOAD_RATE1_1HZ;
 					break;
 				case UBX_CONFIG_STATE_MSG_NAV_SOL:
 					cfg_msg_packet.msgClass_payload = UBX_CLASS_NAV;
@@ -232,16 +243,14 @@ UBX::configure(bool &config_needed, bool &baudrate_changed, unsigned &baudrate,
 			memcpy(&(buffer[2]), &cfg_msg_packet, sizeof(cfg_msg_packet));
 			length = sizeof(cfg_msg_packet)+2;
 		}
-	} else {
-		_waited++;
 	}
 }
 
 int
-UBX::parse(uint8_t b, struct vehicle_gps_position_s* gps_position)
+UBX::parse(uint8_t b, struct vehicle_gps_position_s *gps_position)
 {
+	/* if no error happens and no new report is ready yet, ret will stay 0 */
 	int ret = 0;
-	//printf("Received char: %c\n", b);
 
 	switch (_decode_state) {
 		/* First, look for sync1 */
@@ -373,6 +382,7 @@ UBX::parse(uint8_t b, struct vehicle_gps_position_s* gps_position)
 				default: //should not happen because we set the class
 					warnx("UBX Error, we set a class that we don't know");
 					decodeInit();
+					ret = -1;
 					break;
 				}
 				break;
@@ -415,8 +425,6 @@ UBX::parse(uint8_t b, struct vehicle_gps_position_s* gps_position)
 
 								// Reset state machine to decode next packet
 								decodeInit();
-								return ret;
-
 								break;
 							}
 
@@ -441,8 +449,6 @@ UBX::parse(uint8_t b, struct vehicle_gps_position_s* gps_position)
 
 								// Reset state machine to decode next packet
 								decodeInit();
-								return ret;
-
 								break;
 							}
 
@@ -466,8 +472,6 @@ UBX::parse(uint8_t b, struct vehicle_gps_position_s* gps_position)
 
 								// Reset state machine to decode next packet
 								decodeInit();
-								return ret;
-
 								break;
 							}
 
@@ -501,8 +505,6 @@ UBX::parse(uint8_t b, struct vehicle_gps_position_s* gps_position)
 
 								// Reset state machine to decode next packet
 								decodeInit();
-								return ret;
-
 								break;
 							}
 
@@ -594,8 +596,6 @@ UBX::parse(uint8_t b, struct vehicle_gps_position_s* gps_position)
 
 								// Reset state machine to decode next packet
 								decodeInit();
-								return ret;
-
 								break;
 							}
 
@@ -615,7 +615,6 @@ UBX::parse(uint8_t b, struct vehicle_gps_position_s* gps_position)
 
 									gps_position->counter++;
 
-
 									_new_nav_velned = true;
 
 								} else {
@@ -624,8 +623,6 @@ UBX::parse(uint8_t b, struct vehicle_gps_position_s* gps_position)
 
 								// Reset state machine to decode next packet
 								decodeInit();
-								return ret;
-
 								break;
 							}
 
@@ -718,7 +715,6 @@ UBX::parse(uint8_t b, struct vehicle_gps_position_s* gps_position)
 
 							// Reset state machine to decode next packet
 							decodeInit();
-							return ret;
 
 							break;
 						}
@@ -730,7 +726,7 @@ UBX::parse(uint8_t b, struct vehicle_gps_position_s* gps_position)
 							//Check if checksum is valid
 							if (_rx_ck_a == packet->ck_a && _rx_ck_b == packet->ck_b) {
 
-								warnx("UBX: NO ACK");
+								warnx("UBX: Received: Not Acknowledged");
 								ret = 1;
 
 							} else {
@@ -751,11 +747,12 @@ UBX::parse(uint8_t b, struct vehicle_gps_position_s* gps_position)
 							break;
 						}
 					} // end if _rx_count high enough
-					if (_rx_count < RECV_BUFFER_SIZE) {
+					else if (_rx_count < RECV_BUFFER_SIZE) {
 						_rx_count++;
 					} else {
-						warnx("buffer overflow");
+						warnx("buffer full, restarting");
 						decodeInit();
+						ret = -1;
 					}
 				break;
 		default:
@@ -765,13 +762,16 @@ UBX::parse(uint8_t b, struct vehicle_gps_position_s* gps_position)
 	/* return 1 when position updates and the remaining packets updated at least once */
 	if(_new_nav_posllh &&_new_nav_timeutc && _new_nav_dop && _new_nav_sol && _new_nav_velned) {
 
+		/* Add timestamp to finish the report */
 		gps_position->timestamp = hrt_absolute_time();
-		ret = 1;
+		/* Reset the flags */
 		_new_nav_posllh = false;
-		// _new_nav_timeutc = false;
-		// _new_nav_dop = false;
-		// _new_nav_sol = false;
-		// _new_nav_velned = false;
+		_new_nav_timeutc = false;
+		_new_nav_dop = false;
+		_new_nav_sol = false;
+		_new_nav_velned = false;
+
+		ret = 1;
 	}
 
 	return ret;
@@ -807,6 +807,7 @@ UBX::addChecksumToMessage(uint8_t* message, const unsigned length)
 		ck_a = ck_a + message[i];
 		ck_b = ck_b + ck_a;
 	}
+	/* The checksum is written to the last to bytes of a message */
 	message[length-2] = ck_a;
 	message[length-1] = ck_b;
 }

apps/drivers/gps/ubx.h

@@ -40,16 +40,17 @@
 
 #include "gps_helper.h"
 
-#define UBX_NO_OF_MESSAGES 7								/**< Read 7 UBX GPS messages */
 
 #define UBX_SYNC1 0xB5
 #define UBX_SYNC2 0x62
 
-//UBX Protocol definitions (this is the subset of the messages that are parsed)
+/* ClassIDs (the ones that are used) */
 #define UBX_CLASS_NAV 0x01
 //#define UBX_CLASS_RXM 0x02
 #define UBX_CLASS_ACK 0x05
 #define UBX_CLASS_CFG 0x06
+
+/* MessageIDs (the ones that are used) */
 #define UBX_MESSAGE_NAV_POSLLH 0x02
 #define UBX_MESSAGE_NAV_SOL 0x06
 #define UBX_MESSAGE_NAV_TIMEUTC 0x21
@@ -65,11 +66,11 @@
 #define UBX_MESSAGE_CFG_RATE 0x08
 
 #define UBX_CFG_PRT_LENGTH 20
-#define UBX_CFG_PRT_PAYLOAD_PORTID 0x01         /**< port 1 */
+#define UBX_CFG_PRT_PAYLOAD_PORTID 0x01         /**< UART1 */
 #define UBX_CFG_PRT_PAYLOAD_MODE 0x000008D0     /**< 0b0000100011010000: 8N1 */
 #define UBX_CFG_PRT_PAYLOAD_BAUDRATE 38400      /**< always choose 38400 as GPS baudrate */
-#define UBX_CFG_PRT_PAYLOAD_INPROTOMASK 0x01    /**< ubx in */
-#define UBX_CFG_PRT_PAYLOAD_OUTPROTOMASK 0x01   /**< ubx out */
+#define UBX_CFG_PRT_PAYLOAD_INPROTOMASK 0x01    /**< UBX in */
+#define UBX_CFG_PRT_PAYLOAD_OUTPROTOMASK 0x01   /**< UBX out */
 
 #define UBX_CFG_RATE_LENGTH 6
 #define UBX_CFG_RATE_PAYLOAD_MEASRATE 200		/**< 200ms for 5Hz */
@@ -83,30 +84,30 @@
 #define UBX_CFG_NAV5_PAYLOAD_FIXMODE 2          /**< 1: 2D only, 2: 3D only, 3: Auto 2D/3D */
 
 #define UBX_CFG_MSG_LENGTH 8
-#define UBX_CFG_MSG_PAYLOAD_RATE1 0x01 			/**< {0x00, 0x01, 0x00, 0x00, 0x00, 0x00} UART1 chosen */
-
+#define UBX_CFG_MSG_PAYLOAD_RATE1_5HZ 0x01 		/**< {0x00, 0x01, 0x00, 0x00, 0x00, 0x00} the second entry is for UART1 */
+#define UBX_CFG_MSG_PAYLOAD_RATE1_1HZ 0x05		/**< {0x00, 0x05, 0x00, 0x00, 0x00, 0x00} the second entry is for UART1 */
 
 // ************
 /** the structures of the binary packets */
 #pragma pack(push, 1)
 
 typedef struct {
-	uint32_t time_milliseconds; // GPS Millisecond Time of Week
-	int32_t lon;  // Longitude * 1e-7, deg
-	int32_t lat; // Latitude * 1e-7, deg
-	int32_t height;  // Height above Ellipsoid, mm
-	int32_t height_msl;  // Height above mean sea level, mm
-	uint32_t hAcc;  // Horizontal Accuracy Estimate, mm
-	uint32_t vAcc;  // Vertical Accuracy Estimate, mm
+	uint32_t time_milliseconds;		/**<  GPS Millisecond Time of Week */
+	int32_t lon;					/**<  Longitude * 1e-7, deg */
+	int32_t lat;					/**<  Latitude * 1e-7, deg */
+	int32_t height;					/**<  Height above Ellipsoid, mm */
+	int32_t height_msl;				/**<  Height above mean sea level, mm */
+	uint32_t hAcc;  				/**< Horizontal Accuracy Estimate, mm */
+	uint32_t vAcc;  				/**< Vertical Accuracy Estimate, mm */
 	uint8_t ck_a;
 	uint8_t ck_b;
 } gps_bin_nav_posllh_packet_t;
 
 typedef struct {
-	uint32_t time_milliseconds; // GPS Millisecond Time of Week
-	int32_t time_nanoseconds; // Fractional Nanoseconds remainder of rounded ms above, range -500000 .. 500000
-	int16_t week; // GPS week (GPS time)
-	uint8_t gpsFix; //GPS Fix: 0 = No fix, 1 = Dead Reckoning only, 2 = 2D fix, 3 = 3d-fix, 4 = GPS + dead reckoning, 5 = time only fix
+	uint32_t time_milliseconds; 	/**< GPS Millisecond Time of Week */
+	int32_t time_nanoseconds;		/**< Fractional Nanoseconds remainder of rounded ms above, range -500000 .. 500000 */
+	int16_t week;					/**< GPS week (GPS time) */
+	uint8_t gpsFix;					/**< GPS Fix: 0 = No fix, 1 = Dead Reckoning only, 2 = 2D fix, 3 = 3d-fix, 4 = GPS + dead reckoning, 5 = time only fix */
 	uint8_t flags;
 	int32_t ecefX;
 	int32_t ecefY;
@@ -125,50 +126,50 @@ typedef struct {
 } gps_bin_nav_sol_packet_t;
 
 typedef struct {
-	uint32_t time_milliseconds; // GPS Millisecond Time of Week
-	uint32_t time_accuracy;  //Time Accuracy Estimate, ns
-	int32_t time_nanoseconds; //Nanoseconds of second, range -1e9 .. 1e9 (UTC)
-	uint16_t year; //Year, range 1999..2099 (UTC)
-	uint8_t month; //Month, range 1..12 (UTC)
-	uint8_t day; //Day of Month, range 1..31 (UTC)
-	uint8_t hour; //Hour of Day, range 0..23 (UTC)
-	uint8_t min; //Minute of Hour, range 0..59 (UTC)
-	uint8_t sec; //Seconds of Minute, range 0..59 (UTC)
-	uint8_t valid_flag; //Validity Flags (see ubx documentation)
+	uint32_t time_milliseconds;		/**< GPS Millisecond Time of Week */
+	uint32_t time_accuracy; 		/**< Time Accuracy Estimate, ns */
+	int32_t time_nanoseconds; 		/**< Nanoseconds of second, range -1e9 .. 1e9 (UTC) */
+	uint16_t year; 					/**< Year, range 1999..2099 (UTC) */
+	uint8_t month; 					/**< Month, range 1..12 (UTC) */
+	uint8_t day; 					/**< Day of Month, range 1..31 (UTC) */
+	uint8_t hour; 					/**< Hour of Day, range 0..23 (UTC) */
+	uint8_t min; 					/**< Minute of Hour, range 0..59 (UTC) */
+	uint8_t sec; 					/**< Seconds of Minute, range 0..59 (UTC) */
+	uint8_t valid_flag; 			/**< Validity Flags (see ubx documentation) */
 	uint8_t ck_a;
 	uint8_t ck_b;
 } gps_bin_nav_timeutc_packet_t;
 
 typedef struct {
-	uint32_t time_milliseconds; // GPS Millisecond Time of Week
-	uint16_t gDOP; //Geometric DOP (scaling 0.01)
-	uint16_t pDOP; //Position DOP (scaling 0.01)
-	uint16_t tDOP; //Time DOP (scaling 0.01)
-	uint16_t vDOP; //Vertical DOP (scaling 0.01)
-	uint16_t hDOP; //Horizontal DOP (scaling 0.01)
-	uint16_t nDOP; //Northing DOP (scaling 0.01)
-	uint16_t eDOP; //Easting DOP (scaling 0.01)
+	uint32_t time_milliseconds; 	/**<  GPS Millisecond Time of Week */
+	uint16_t gDOP; 					/**< Geometric DOP (scaling 0.01) */
+	uint16_t pDOP; 					/**< Position DOP (scaling 0.01) */
+	uint16_t tDOP; 					/**< Time DOP (scaling 0.01) */
+	uint16_t vDOP; 					/**< Vertical DOP (scaling 0.01) */
+	uint16_t hDOP; 					/**< Horizontal DOP (scaling 0.01) */
+	uint16_t nDOP; 					/**< Northing DOP (scaling 0.01) */
+	uint16_t eDOP; 					/**< Easting DOP (scaling 0.01) */
 	uint8_t ck_a;
 	uint8_t ck_b;
 } gps_bin_nav_dop_packet_t;
 
 typedef struct {
-	uint32_t time_milliseconds; // GPS Millisecond Time of Week
-	uint8_t numCh; //Number of channels
+	uint32_t time_milliseconds; 	/**<  GPS Millisecond Time of Week */
+	uint8_t numCh; 					/**< Number of channels */
 	uint8_t globalFlags;
 	uint16_t reserved2;
 
 } gps_bin_nav_svinfo_part1_packet_t;
 
 typedef struct {
-	uint8_t chn; //Channel number, 255 for SVs not assigned to a channel
-	uint8_t svid; //Satellite ID
+	uint8_t chn; 					/**< Channel number, 255 for SVs not assigned to a channel */
+	uint8_t svid; 					/**< Satellite ID */
 	uint8_t flags;
 	uint8_t quality;
-	uint8_t cno; //Carrier to Noise Ratio (Signal Strength), dbHz
-	int8_t elev; //Elevation in integer degrees
-	int16_t azim; //Azimuth in integer degrees
-	int32_t prRes; //Pseudo range residual in centimetres
+	uint8_t cno; 					/**< Carrier to Noise Ratio (Signal Strength), dbHz */
+	int8_t elev; 					/**< Elevation in integer degrees */
+	int16_t azim; 					/**< Azimuth in integer degrees */
+	int32_t prRes; 					/**< Pseudo range residual in centimetres */
 
 } gps_bin_nav_svinfo_part2_packet_t;
 
@@ -192,9 +193,9 @@ typedef struct {
 } gps_bin_nav_velned_packet_t;
 
 //typedef struct {
-//	int32_t time_milliseconds; // Measurement integer millisecond GPS time of week
-//	int16_t week; //Measurement GPS week number
-//	uint8_t numVis; //Number of visible satellites
+//	int32_t time_milliseconds; 		/**< Measurement integer millisecond GPS time of week */
+//	int16_t week; 					/**< Measurement GPS week number */
+//	uint8_t numVis;					/**< Number of visible satellites */
 //
 //	//... rest of package is not used in this implementation
 //
@@ -210,7 +211,6 @@ typedef struct {
 typedef struct {
 	uint8_t clsID;
 	uint8_t msgID;
-
 	uint8_t ck_a;
 	uint8_t ck_b;
 } gps_bin_ack_nak_packet_t;
@@ -340,17 +340,27 @@ class UBX : public GPS_Helper
 public:
 	UBX();
 	~UBX();
-
-	void				configure(bool&, bool&, unsigned&, uint8_t*, int&, const unsigned);
+	void				reset(void);
+	void				configure(bool &config_needed, bool &baudrate_changed, unsigned &baudrate, uint8_t *buffer, int &length, const unsigned max_length);
 	int 				parse(uint8_t, struct vehicle_gps_position_s*);
 
 private:
+	/**
+	 * Reset the parse state machine for a fresh start
+	 */
 	void				decodeInit(void);
+
+	/**
+	 * While parsing add every byte (except the sync bytes) to the checksum
+	 */
 	void				addByteToChecksum(uint8_t);
+
+	/**
+	 * Add the two checksum bytes to an outgoing message
+	 */
 	void				addChecksumToMessage(uint8_t*, const unsigned);
-	unsigned			_waited;
-	bool 				_waiting_for_ack;
 	ubx_config_state_t	_config_state;
+	bool 				_waiting_for_ack;
 	ubx_decode_state_t	_decode_state;
 	uint8_t				_rx_buffer[RECV_BUFFER_SIZE];
 	unsigned			_rx_count;