class Gps(Node):
ON = b"\x00\x01\x01\x01\x00\x00"
OFF = b"\x00\x00\x00\x00\x00\x00"
PORT = "/dev/ttyACM0"
BAUDRATE = 9600
TIMEOUT = 1
UBXONLY = False
def __init__(self):
super().__init__('gps')
# setup the GPS
self.declare_parameter('gps_baud', self.BAUDRATE)
self.declare_parameter('gps_port', self.PORT)
self.baud = self.get_parameter('gps_baud').value
self.port = self.get_parameter('gps_port').value
self.ubp = GPSReader(self.port, self.baud,
self.TIMEOUT, self.UBXONLY)
if not self.ubp.connect():
# TODO: raise custom error
self.get_logger().error(f"GPS Failed to connect on given port. Aborting")
return
self.ubp.config_timepulse_badly()
self.ubp.config_msg(self.ON)
# setup the ROS
self.declare_parameter('gps_top', 'gps')
self.declare_parameter('time_top', 'gps_time')
pub_top = self.get_parameter('gps_top').value
time_top = self.get_parameter('time_top').value
self.fix_pub = self.create_publisher(NavSatFix, pub_top, 10)
self.time_pub = self.create_publisher(TimeReference, time_top, 10)
# setup the gpio
GPIO.setmode(GPIO.BCM)
GPIO.setup(26, GPIO.IN, GPIO.PUD_UP)
GPIO.add_event_detect(26, GPIO.RISING,
callback=self.timepulse_callback, bouncetime=50)
def timepulse_callback(self, channel):
self.get_logger().info(f"{time.time()} Timepulse trigger")
gps_msg = NavSatFix()
timeref_msg = TimeReference()
msg_hdr = Header()
system_time = self.get_clock().now().to_msg()
msg_hdr.frame_id = 'base_link' # center of the plane
try:
ubx = self.ubp.read()
except IOError:
self.get_logger().warning("GPS disconnected. Attempting to reconnect.")
self.ubp = GPSReader(self.port, self.baud,
self.TIMEOUT, self.UBXONLY)
return
while ubx:
if (ubx.msg_cls + ubx.msg_id) == b"\x01\x07": # NAV_PVT
# <UBX(NAV-PVT, iTOW=16:50:32, year=2015, month=10, day=25, hour=16, min=50, second=48, valid=b'\xf0', tAcc=4294967295, nano=0, fixType=0, flags=b'\x00', flags2=b'$', numSV=0, lon=0, lat=0, height=0, hMSL=-17000, hAcc=4294967295, vAcc=4294967295, velN=0, velE=0, velD=0, gSpeed=0, headMot=0, sAcc=20000, headAcc=18000000, pDOP=9999, reserved1=65034815406080, headVeh=0, magDec=0, magAcc=0)>
msg_hdr.stamp = self._gen_timestamp_from_utc(ubx)
fix_stat = NavSatStatus()
if ubx.fixType == 0:
self.get_logger().warning(f"No fix yet.")
break
fix_stat.service = SERVICE_GPS
gps_msg.status = fix_stat
gps_msg.header = msg_hdr
gps_msg.latitude = float(ubx.lat)/10000000
gps_msg.longitude = float(ubx.lon)/10000000
gps_msg.altitude = float(ubx.height)/1000
timeref_msg.header = msg_hdr
timeref_msg.time_ref = system_time
timeref_msg.source = "GPS"
self.fix_pub.publish(gps_msg)
self.time_pub.publish(timeref_msg)
self.get_logger().info(f"Publishing gps message: ({timeref_msg.header.stamp.sec}.{timeref_msg.header.stamp.nanosec}): ({gps_msg.latitude}, {gps_msg.longitude}, {gps_msg.altitude})")
return
else:
self.get_logger().info(f"Other GPS MSG: {(ubx.msg_cls + ubx.msg_id)}")
ubx = self.ubp.read()
def _gen_timestamp_from_utc(self, ubx):
second = ubx.second
usecond = ubx.nano/1000
subtract_sec = False
if usecond < 0:
usecond = 1000000 + usecond
subtract_sec = True
utc = datetime.datetime(ubx.year, ubx.month, ubx.day, ubx.hour, ubx.min, second, int(usecond))
gps_time = utc.timestamp()
if subtract_sec:
gps_time -= 1
gps_stamp = self.get_clock().now().to_msg()
gps_stamp.sec = int(gps_time)
gps_stamp.nanosec = int((gps_time - int(gps_time))*1000000000)
return gps_stamp
