From a5ea08c5a3a2d3ecdfb1f5f8b4fffb1b2c3d0064 Mon Sep 17 00:00:00 2001
From: Calvin <calvin.mccoy@gmail.com>
Date: Tue, 9 Dec 2014 18:47:15 -0500
Subject: [PATCH] Intial commit: basic stream parsing with support for RMC,
VTG, and GGA sentences.
---
micropyGPS.py | 363 ++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 363 insertions(+)
create mode 100644 micropyGPS.py
diff --git a/micropyGPS.py b/micropyGPS.py
new file mode 100644
index 0000000..3664b55
--- /dev/null
+++ b/micropyGPS.py
@@ -0,0 +1,363 @@
+from struct import *
+
+# TODO:
+# GSA Sentence
+# GSV Sentence
+# Time Since First Fix
+# Time Since Last Good Fix
+# Statistics
+
+test_RMC = ['$GPRMC,081836,A,3751.65,S,14507.36,E,000.0,360.0,130998,011.3,E*62',
+ '$GPRMC,123519,A,4807.038,N,01131.000,E,022.4,084.4,230394,003.1,W*6A',
+ '$GPRMC,225446,A,4916.45,N,12311.12,W,000.5,054.7,191194,020.3,E*68',
+ '$GPRMC,180041.896,A,3749.1851,N,08338.7891,W,001.9,154.9,240911,,,A*7A',
+ '$GPRMC,180049.896,A,3749.1808,N,08338.7869,W,001.8,156.3,240911,,,A*70',
+ '$GPRMC,092751.000,A,5321.6802,N,00630.3371,W,0.06,31.66,280511,,,A*45']
+
+test_VTG = ['$GPVTG,232.9,T,,M,002.3,N,004.3,K,A*01']
+test_GGA = ['$GPGGA,180050.896,3749.1802,N,08338.7865,W,1,07,1.1,397.4,M,-32.5,M,,0000*6C']
+test_GSA = ['$GPGSA,A,3,07,11,28,24,26,08,17,,,,,,2.0,1.1,1.7*37']
+test_GSV = ['$GPGSV,3,1,12,28,72,355,39,01,52,063,33,17,51,272,44,08,46,184,38*74',
+ '$GPGSV,3,2,12,24,42,058,33,11,34,053,33,07,20,171,40,20,15,116,*71',
+ '$GPGSV,3,3,12,04,12,204,34,27,11,324,35,32,11,089,,26,10,264,40*7B']
+
+
+class MicroGPSpy(object):
+ """GPS NMEA Sentence Parser"""
+
+ def __init__(self, local_offset=0):
+ """Setup GPS Object Status Flags, Internal Data Registers, etc"""
+
+ #####################
+ # Object Status Flags
+ self.sentence_active = False
+ self.active_segment = 0
+ self.process_crc = False
+ self.gps_segments = []
+ self.crc_xor = 0
+
+ #####################
+ # Data From Sentences
+ # Time
+ self.timestamp = (0, 0, 0)
+ self.date = (0, 0, 0)
+ self.local_offset = local_offset
+
+ # Position/Motion
+ self.latitude = (0, 0.0, 'N')
+ self.longitude = (0, 0.0, 'W')
+ self.speed = (0.0, 0.0, 0.0)
+ self.course = 0.0
+ self.altitude = 0.0
+ self.geoid_height = 0.0
+
+ # GPS Info
+ self.sats_in_view = 0
+ self.sats_in_use = 0
+ self.hdop = 0.0
+ self.pdop = 0.0
+ self.vdop = 0.0
+ self.valid = False
+ self.fix_stat = 0
+ self.fix_type = 1
+
+ # Object Constants
+ self.__hemispheres = ('N', 'S', 'E', 'W')
+
+ # Recommended minimum specific GPS/Transit data
+ def gprmc(self):
+ """Parse Recommended Minimum Specific GPS/Transit data (RMC)Sentence. Updates UTC timestamp, latitude,
+ longitude, Course, Speed, and Date"""
+
+ # UTC Timestamp
+ try:
+ utc_string = self.gps_segments[1]
+ # Skip timestamp if receiver doesn't have one yet
+ if utc_string:
+ hours = int(utc_string[0:2]) + self.local_offset
+ minutes = int(utc_string[2:4])
+ seconds = float(utc_string[4:])
+ self.timestamp = (hours, minutes, seconds)
+ except ValueError:
+ return False
+
+ # Check Receiver Data Valid Flag
+ if self.gps_segments[2] == 'A': # Data from Receiver is valid
+
+ # Longitude / Latitude
+ try:
+ # Latitude
+ l_string = self.gps_segments[3]
+ lat_degs = int(l_string[0:2])
+ lat_mins = float(l_string[2:])
+ lat_hemi = self.gps_segments[4]
+
+ # Longitude
+ l_string = self.gps_segments[5]
+ lon_degs = int(l_string[0:3])
+ lon_mins = float(l_string[3:])
+ lon_hemi = self.gps_segments[6]
+ except ValueError:
+ return False
+
+ if lat_hemi not in self.__hemispheres:
+ return False
+
+ if lon_hemi not in self.__hemispheres:
+ return False
+
+ # Speed
+ try:
+ spd_knt = float(self.gps_segments[7])
+ except ValueError:
+ return False
+
+ # Date
+ try:
+ # NOTE!!! Date string is assumed to be year >=2000,
+ # Sentences recorded in 90s will display as 209X!!!
+ # FIXME if you want to parse old GPS logs or are time traveler
+ date_string = self.gps_segments[9]
+ day = date_string[0:2]
+ month = date_string[2:4]
+ year = date_string[4:6]
+ except ValueError:
+ return False
+
+ # Course
+ try:
+ course = self.gps_segments[8]
+ except ValueError:
+ return False
+
+ # TODO - Add Magnetic Variation
+
+ # Update Object Data
+ self.latitude = (lat_degs, lat_mins, lat_hemi)
+ self.longitude = (lon_degs, lon_mins, lon_hemi)
+ # Include mph and hm/h
+ self.speed = (spd_knt, spd_knt * 1.151, spd_knt * 1.852)
+ self.date = (day, month, year)
+ self.course = course
+ self.valid = True
+
+ else:
+ return False
+
+ return True
+
+ def gpvtg(self):
+ """Parse Track Made Good and Ground Speed (VTG) Sentence. Updates speed and course"""
+ try:
+ course = self.gps_segments[1]
+ spd_knt = float(self.gps_segments[5])
+ except ValueError:
+ return False
+
+ # Include mph and hm/h
+ self.speed = (spd_knt, spd_knt * 1.151, spd_knt * 1.852)
+ self.course = course
+ return True
+
+ def gpgga(self):
+ """Parse Global Positioning System Fix Data (GGA) Sentence. Updates UTC timestamp, latitude, longitude,
+ fix status, satellites in use, Horizontal Dilution of Precision (HDOP), altitude, and geoid height"""
+
+ # UTC Timestamp
+ try:
+ utc_string = self.gps_segments[1]
+ # Skip timestamp if receiver doesn't have on yet
+ if utc_string:
+ hours = int(utc_string[0:2]) + self.local_offset
+ minutes = int(utc_string[2:4])
+ seconds = float(utc_string[4:])
+ self.timestamp = (hours, minutes, seconds)
+ except ValueError:
+ return False
+
+ # Number of Satellites in Use
+ try:
+ self.sats_in_use = int(self.gps_segments[7])
+ except ValueError:
+ return False
+
+ # Horizontal Dilution of Precision
+ try:
+ self.hdop = float(self.gps_segments[8])
+ except ValueError:
+ return False
+
+ # Get Fix Status
+ try:
+ self.fix_stat = int(self.gps_segments[6])
+ except ValueError:
+ return False
+
+ # Process Location and Speed Data if Fix is GOOD
+ if self.fix_stat:
+
+ # Longitude / Latitude
+ try:
+ # Latitude
+ l_string = self.gps_segments[2]
+ lat_degs = int(l_string[0:2])
+ lat_mins = float(l_string[2:])
+ lat_hemi = self.gps_segments[3]
+
+ # Longitude
+ l_string = self.gps_segments[4]
+ lon_degs = int(l_string[0:3])
+ lon_mins = float(l_string[3:])
+ lon_hemi = self.gps_segments[5]
+ except ValueError:
+ return False
+
+ if lat_hemi not in self.__hemispheres:
+ return False
+
+ if lon_hemi not in self.__hemispheres:
+ return False
+
+ # Altitude / Height Above Geoid
+ try:
+ altitude = float(self.gps_segments[9])
+ geoid_height = float(self.gps_segments[11])
+ except ValueError:
+ return False
+
+ # Update Object Data
+ self.latitude = (lat_degs, lat_mins, lat_hemi)
+ self.longitude = (lon_degs, lon_mins, lon_hemi)
+ self.altitude = altitude
+ self.geoid_height = geoid_height
+
+ return True
+
+ def gpgsa(self):
+ pass
+
+ def gpgsv(self):
+ pass
+
+ def new_sentence(self):
+ """Adjust Object Flags in Preparation for a New Sentence"""
+ self.gps_segments = ['']
+ self.active_segment = 0
+ self.crc_xor = 0
+ self.sentence_active = True
+ self.process_crc = True
+
+ def update(self, new_char):
+ """Process a new input char and updates GPS object if necessary based on special characters ('$', ',', '*')
+ Function builds a list of received string that are validate by CRC prior to parsing by the appropriate
+ sentence function. Returns sentence type on successful parse, None otherwise"""
+
+ valid_sentence = False
+
+ # Validate new_char is a printable char
+ ascii_char = ord(new_char)
+
+ if 33 <= ascii_char <= 126:
+
+ # Check if a new string is starting ($)
+ if new_char == '$':
+ self.new_sentence()
+ return False
+
+ # Check if sentence is ending (*)
+ elif new_char == '*':
+ self.process_crc = False
+ self.active_segment += 1
+ self.gps_segments.append('')
+ return False
+
+ # Check if a section is ended (,), Create a new substring to feed
+ # characters to
+ elif new_char == ',':
+ self.active_segment += 1
+ self.gps_segments.append('')
+
+ # Store All Other printable character and check CRC when ready
+ else:
+ if self.sentence_active:
+ self.gps_segments[self.active_segment] += new_char
+
+ # When CRC input is disabled, sentence is nearly complete
+ if not self.process_crc:
+
+ if len(self.gps_segments[self.active_segment]) == 2:
+ try:
+ final_crc = int(self.gps_segments[self.active_segment], 16)
+ if self.crc_xor == final_crc:
+ valid_sentence = True
+ except ValueError:
+ pass # CRC Value was deformed and could not have been correct
+
+ # Update CRC
+ if self.process_crc:
+ self.crc_xor ^= ascii_char
+
+ # If a Valid Sentence Was received and it's a supported sentence, then
+ # parse it!!
+ if valid_sentence and self.gps_segments[0] in self.supported_sentences:
+
+ # Clear Active Processing Flag
+ self.sentence_active = False
+
+ # parse the Sentence Based on the message type, return True if
+ # parse is clean
+ if self.supported_sentences[self.gps_segments[0]](self):
+ # Let host know that the GPS object was updated by returning
+ # parsed sentence type
+ return self.gps_segments[0]
+
+ # Tell Host no new sentence was parsed
+ return None
+
+ # All the currently supported NMEA sentences
+ supported_sentences = {'GPRMC': gprmc, 'GPGGA': gpgga, 'GPVTG': gpvtg, 'GPGSA': gpgsa, 'GPGSV': gpgsv}
+
+
+if __name__ == "__main__":
+
+ my_gps = MicroGPSpy()
+ sentence = ''
+ for RMC_sentence in test_RMC:
+ for y in RMC_sentence:
+ sentence = my_gps.update(y)
+ print('Parsed a', sentence, 'Sentence')
+ print('Parsed Strings:', my_gps.gps_segments)
+ print('Sentence CRC Value:', hex(my_gps.crc_xor))
+ print('Longitude:', my_gps.longitude)
+ print('Latitude', my_gps.latitude)
+ print('UTC Timestamp:', my_gps.timestamp)
+ print('Speed:', my_gps.speed)
+ print('Date Stamp:', my_gps.date)
+ print('Course', my_gps.course)
+ print('Data is Valid', my_gps.valid)
+ print('')
+
+ for VTG_sentence in test_VTG:
+ for y in VTG_sentence:
+ sentence = my_gps.update(y)
+ print('Parsed a', sentence, 'Sentence')
+ print('Parsed Strings', my_gps.gps_segments)
+ print('Sentence CRC Value:', hex(my_gps.crc_xor))
+ print('Speed:', my_gps.speed)
+ print('Course', my_gps.course)
+ print('')
+
+ for GGA_sentence in test_GGA:
+ for y in GGA_sentence:
+ sentence = my_gps.update(y)
+ print('Parsed a', sentence, 'Sentence')
+ print('Parsed Strings', my_gps.gps_segments)
+ print('Sentence CRC Value:', hex(my_gps.crc_xor))
+ print('Longitude', my_gps.longitude)
+ print('Latitude', my_gps.latitude)
+ print('UTC Timestamp:', my_gps.timestamp)
+ print('Fix Status:', my_gps.fix_stat)
+ print('Altitude:', my_gps.altitude)
+ print('Height Above Geoid:', my_gps.geoid_height)
+ print('Horizontal Dilution of Precision:', my_gps.hdop)
+ print('Satellites in Use by Receiver:', my_gps.sats_in_use)