# Example: GPS Position Logging Program """ Latitude and longitude are recorded as measurements. A script task runs periodically: * Task ensures the GPS is on * Task reads the position for the GPS and stores it into global variables Two measurements are associated with scripts: * One reads the latitude from the global variable * The other reads the longitude from the global variable * The measurements need to be scheduled right after the script task A Sat/XLink setup is associated with this module: `gps_tracker_setup.txt `_ """ import re from sl3 import * def convert_to_decimal_degrees(degrees, minutes, seconds): """ converts degrees minutes seconds into degrees with decimal places""" result = float(degrees) + float(minutes) / 60.0 + float(seconds) / (60 * 60); return result def gps_parse_lat_long(gps_status): """ Parses Satlink's STATUS GPS looking for the latitude and longitude. Example reply when no locati on:: GPS Sync in progress GPS tracking satellites Clock has NOT been synced to GPS. Signal Quality (SatID/Signal CNo): 1/46 3/46 6/43 11/38 17/45 18/36 19/40 22/42 24/37 28/43 at 2018/08/14 15:12:26 And with location:: GPS Sync in progress GPS acquiring almanac Last sync to GPS was at 2018/08/14 15:12:48 Last sync is valid till 2018/09/13 15:12:48 GPS was powered for 00::00:01:04 before it acquired satellite lock Lat N 38o 59' 50.01" Long W 77o 25' 24.46" Alt 134.6m(441.5ft) Signal Quality (SatID/Signal CNo): 1/44 3/45 6/41 11/34 17/45 18/35 19/39 22/41 24/34 28/41 at 2018/08/14 15:12:41 We want this line:: Lat N 38o 59' 50.01" Long W 77o 25' 24.46" Alt 134.6m(441.5ft) """ # split it into lines lines = gps_status.split("\r\n") # go through each line, looking for Lat and Long found = False for lat_long_line in lines: if ("Lat" in lat_long_line) and ("Long" in lat_long_line): found = True break if found: # strip leading whitespace clean_line = lat_long_line.lstrip() # split the string into tokens separated by space tokens = clean_line.split(' ') # this regular expression will match a number at the start of the string number_parse = re.compile(r"\d+\.*\d*") # parse and convert the numbers to ints and floats try: lat_deg = int(number_parse.match(tokens[2]).group(0)) lat_min = int(number_parse.match(tokens[3]).group(0)) lat_sec = float(number_parse.match(tokens[4]).group(0)) long_deg = int(number_parse.match(tokens[7]).group(0)) long_min = int(number_parse.match(tokens[8]).group(0)) long_sec = float(number_parse.match(tokens[9]).group(0)) # compute latitude latitude = convert_to_decimal_degrees(lat_deg, lat_min, lat_sec) # Latitude North means positive degrees, South means negative if "Lat S" in lat_long_line: latitude = -latitude # compute longitude longitude = convert_to_decimal_degrees(long_deg, long_min, long_sec) # Longitude West means negative degrees if "Long W" in lat_long_line: longitude = -longitude return latitude, longitude except ValueError: pass except IndexError: pass # if we got this far, our string did not contain the expected numbers return 0.0, 0.0 def gps_read_position(): """ Gets the current STATUS GPS and parses the location from it. :return: latitude, longitude :rtype: float, float """ # use the command line to read the gps status status = command_line("STATUS GPS", 4 * 1024) # pare the location from the status return gps_parse_lat_long(status ) def test_gps_read_position(): """ Verifies that gps_read_position works""" str1 = \ "GPS Sync in progress GPS acquiring almanac\r\n\ Last sync to GPS was at 2018/08/14 15:12:48\r\n\ Last sync is valid till 2018/09/13 15:12:48\r\n\ GPS was powered for 00::00:01:04 before it acquired satellite lock\r\n\ Lat N 38o 59' 50.01\" Long W 77o 25' 24.46\" Alt 134.6m(441.5ft)\r\n\ Signal Quality (SatID/Signal CNo): 1/44 3/45 6/41 11/34 17/45 18/35 19/39 22/41 24/34 28/41 at 2018/08/14 15:12:41\r\n\ " lat, long = gps_parse_lat_long(str1) # compare the floating point values by subtracting them and # verifying the difference is insignificant assert ((lat - 38.99723) < 0.001) assert ((long - -77.42346) < 0.001) str2 = "" lat, long = gps_parse_lat_long(str2) # compare the floating point values by subtracting them and # verifying the difference is insignificant assert (lat == 0.0) assert (long == 0.0) # we need to check the version of Satlink firmware version_needs_check = True """ In order to assure that both latitude and longitude are read at the same time, we will have a Satlink task read the GPS status and store the latitude and longitude globally.""" m_latitude = 0.0 m_longitude = 0.0 @TASK def gps_keep_on_and_read_position(): """ Task has two functions: * Make sure the GPS stays on all the time * Read the position from the GPS and store it in globals Task should be scheduled to run periodically, every 5 minutes. It should happen 30 seconds before the latitude and longitude meas. """ # The listen command will tell the system to keep GPS on command_line("!LISTEN 3600") # This command will tell the GPS to acquire time and location command_line("!GPS SYNC") # Give the GPS a chance to complete the position acquisition if not is_being_tested(): # if we are testing the scirpt, don't wait utime.sleep(25.0) # Read the GPS position and store it global m_latitude global m_longitude m_latitude, m_longitude = gps_read_position() # Requires Satlink version 2916 or newer global version_needs_check if version_needs_check: if ver()[2] < 2974: raise AssertionError("Upgrade Satlink firmware!") else: version_needs_check = False @MEASUREMENT def meas_latitude(inval): """Associate with a measurement to have it log latitude. The measurement should be setup as manual entry. Please note that this returns a result of zero until the task gps_keep_on_and_read_position is run""" return m_latitude @MEASUREMENT def meas_longitude(inval): """ Like meas_latitude, but for longitude""" return m_longitude @TXFORMAT def append_lat_long(standard): """Appened m_latitude and m_longitude to transmission.""" return "{} latitude= {:.6f}, longitude= {:.6f}".format(standard, m_latitude, m_longitude)