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Software/Python/grove_gps/GroveGPS.py

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+import serial, time
+import smbus
+import math
+import RPi.GPIO as GPIO
+import struct
+import sys
+ 
+ser = serial.Serial('/dev/ttyAMA0',  9600, timeout = 0)	#Open the serial port at 9600 baud
+ser.flush()
+ 
+def readlineCR():
+    rv = ""
+    while True:
+        time.sleep(0.001)	# This is the critical part.  A small pause 
+        					# works really well here.
+        ch = ser.read()        
+        rv += ch
+        if ch=='\r' or ch=='':
+            return rv
+ 
+class GPS:
+	#The GPS module used is a Grove GPS module http://www.seeedstudio.com/depot/Grove-GPS-p-959.html
+	inp=[]
+	# Refer to SIM28 NMEA spec file http://www.seeedstudio.com/wiki/images/a/a0/SIM28_DATA_File.zip
+	GGA=[]
+ 
+	#Read data from the GPS
+	def read(self):	
+		while True:
+			# GPS.inp=ser.readline()
+			GPS.inp = readlineCR().strip()
+			if GPS.inp[:6] =='$GPGGA': # GGA data , packet 1, has all the data we need
+				break
+			time.sleep(0.1)
+		try:
+			ind=GPS.inp.index('$GPGGA',5,len(GPS.inp))	#Sometimes multiple GPS data packets come into the stream. Take the data only after the last '$GPGGA' is seen
+			GPS.inp=GPS.inp[ind:]
+		except ValueError:
+			print ""
+		GPS.GGA=GPS.inp.split(",")	#Split the stream into individual parts
+		return [GPS.GGA]
+ 
+	#Split the data into individual elements
+	def vals(self):
+		time=GPS.GGA[1]
+		lat=GPS.GGA[2]
+		lat_ns=GPS.GGA[3]
+		long=GPS.GGA[4]
+		long_ew=GPS.GGA[5]
+		fix=GPS.GGA[6]
+		sats=GPS.GGA[7]
+		alt=GPS.GGA[9]
+		return [time,fix,sats,alt,lat,lat_ns,long,long_ew]
+ 
+g=GPS()
+f=open("gps_data.csv",'w')	#Open file to log the data
+f.write("name,latitude,longitude\n")	#Write the header to the top of the file
+ind=0
+while True:
+	try:
+		x=g.read()	#Read from GPS
+		[t,fix,sats,alt,lat,lat_ns,long,long_ew]=g.vals()	#Get the individial values
+		print "Time:",t,"Fix status:",fix,"Sats in view:",sats,"Altitude",alt,"Lat:",lat,lat_ns,"Long:",long,long_ew
+		s=str(t)+","+str(float(lat)/100)+","+str(float(long)/100)+"\n"	
+		f.write(s)	#Save to file
+		time.sleep(2)
+	except IndexError:
+		print "Unable to read"
+	except KeyboardInterrupt:
+		f.close()
+		print "Exiting"
+		sys.exit(0)
+	except:
+		print "Raw String appears to be empty."