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#!/usr/bin/env python
#
# gpsprobe -- collect send-cycle and performance statistics on a GPS
from math import *
import time, os
import gps, gpsd, curses.ascii
class Baton:
"Ship progress indication to stderr."
def __init__(self, prompt, endmsg=None):
self.stream = sys.stderr
self.stream.write(prompt + "... \010")
self.stream.flush()
self.count = 0
self.endmsg = endmsg
self.time = time.time()
return
def twirl(self, ch=None):
if self.stream is None:
return
if ch:
self.stream.write(ch)
else:
self.stream.write("-/|\\"[self.count % 4])
self.stream.write("\010")
self.count = self.count + 1
self.stream.flush()
return
def end(self, msg=None):
if msg == None:
msg = self.endmsg
if self.stream:
self.stream.write("...(%2.2f sec) %s.\n" % (time.time() - self.time, msg))
return
def looks_like_NMEA(data):
if data.find("$GP") == -1:
return False
#sys.stderr.write("[%s]" % data)
# It's OK to have leading garbage, but not trailing garbage.
# Leading garbage may just mean the device hasn't settled yet.
# Trailing garbage means that the data accidentally looked like
# NMEA or that old data that really was NMEA happened to be sitting
# in the TTY buffer unread, but the new data we read is not
# sentences.
while not (curses.ascii.isprint(data[0]) or curses.ascii.isspace(data[0])):
data = data[1:]
if not data:
return False
#sys.stderr.write("(%s)" % data)
binary = filter(lambda x: not (curses.ascii.isprint(x) or curses.ascii.isspace(x)), data)
#sys.stderr.write("{"+repr(data)+"}")
return not binary
def looks_like_SiRF(data):
header = data.find("\xa0\xa2")
if header == -1:
return False
# We need a position/velocity/time message, SiRF type 0x02
if len(data) < header+5 or data[header+4] != chr(02):
return False
return True
triggers = {
"PRWIZCH": "# This GPS has a Rockwell Zodiac chipset.\n"
}
GE301 = "# GPVTG format indicates NMEA version >= 3.01.\n"
if __name__ == '__main__':
import sys, getopt
fixes = []
# Process options
(options, arguments) = getopt.getopt(sys.argv[1:], "hn:")
await = 100;
device="/dev/gps"
for (switch, val) in options:
if (switch == '-n'):
await = int(val)
elif (switch == '-h'):
sys.stderr.write("usage: gpsprobe [-h] [-n samplecount] [device]\n")
if arguments:
device = arguments[0]
intervals = {}
last_seen = {}
notifications = []
last_command = None
def roundoff(n):
# Round a time to hundredths of a second
return round(n*100) / 100.0
def register(trait):
if (trait) not in notifications:
notifications.append(trait)
def count(sentence):
global intervals, last_seen, last_command
baton.twirl()
# Toss out everything that doesn't look like well-formed NMEA
fields = sentence.split(",")
leader = fields[0]
if leader and leader[0] == '$':
leader = leader[1:]
else:
return
# Throw out everything but the leader in each GPGSV group
if leader == "GPGSV" and last_command == "GPGSV":
return
last_command = leader
# Record timings
now = time.time()
if not leader in intervals:
intervals[leader] = []
if leader in last_seen:
intervals[leader].append(roundoff(now - last_seen[leader]))
last_seen[leader] = now
# Watch for trigger strings
for string in triggers.keys():
if sentence.find(string) > -1:
register(triggers[string])
if leader == "GPVTG":
if fields[2] == 'T':
register(GE301)
else:
register("GPVTG format indicates NMEA version < 3.01.\n")
if leader == "GPRMC":
if len(fields) > 12 and fields[12] in "ADEMSN":
register("GPRMC format indicates NMEA version >= 2.3.\n")
else:
register("GPRMC format indicates NMEA version < 2.3.\n")
try:
# Step one: Check that we have read permission on the device
if not os.access(device, os.R_OK|os.W_OK):
sys.stderr.write(device + " nonexistent or inaccessible.\n")
sys.exit(0)
# Step two: Open and sync up with the device
dev = gpsd.gpsd(device=device)
if dev.activate() > -1:
sys.stderr.write("Found device at %dbps.\n" % dev.bps)
else:
sys.stderr.write("Couldn't acquire the device.\n")
sys.exit(0)
# Step three: Gather data
starttime = time.time()
dev.set_raw_hook(count)
sys.stderr.write("Gathering %d sentences will probably take about %d seconds.\n"%(await, (await*4800)/(3*dev.bps),))
countdown = await
baton = Baton("Gathering sentences", "done")
while countdown > 0:
if dev.poll() > 0 and dev.latlon_stamp.seen():
if not fixes:
fixtime = (time.time()-starttime,)
fixes.append((dev.latitude, dev.longitude))
baton.twirl()
countdown -= 1
baton.end()
del last_seen
# Step three: get command frequencies and the basic send cycle time
frequencies = {}
for (key, interval_list) in intervals.items():
frequencies[key] = {}
for interval in interval_list:
frequencies[key][interval] = frequencies[key].get(interval, 0) + 1
# filter out noise
for key in frequencies:
distribution = frequencies[key]
for interval in distribution.keys():
if distribution[interval] < 2:
del distribution[interval]
cycles = {}
for key in frequencies:
distribution = frequencies[key]
if len(frequencies[key].values()) == 1:
# The value is uniqe after filtering
cycles[key] = distribution.keys()[0]
else:
# Compute the mode
maxfreq = 0
for (interval, frequency) in distribution.items():
if distribution[interval] > maxfreq:
cycles[key] = interval
maxfreq = distribution[interval]
print "First fix in %f seconds." % fixtime
for key in cycles:
if len(frequencies[key].values()) == 1:
if cycles[key] == 1:
print "%s: is emitted once a second." % key
else:
print "%s: is emitted once every %d seconds." % (key, cycles[key])
else:
if cycles[key] == 1:
print "%s: is probably emitted once a second." % key
else:
print "%s: is probably emitted once every %d seconds." % (key, cycles[key])
sendcycle = min(*cycles.values())
if sendcycle == 1:
print "Send cycle is once per second."
else:
print "Send cycle is once per %d seconds." % sendcycle
# Step four: print out registered traits
sys.stdout.write("".join(notifications) + "\n")
except KeyboardInterrupt:
print "Aborted."
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