Hello @Geraud
I am just going to do a pull request to complete the script nmeaoutput.py with the virtual port integration.
Here is what the python script looks like:
#!/usr/bin/python3
"""
Read position from Water Linked Underwater GPS convert to NMEA and send to serial
port or on UDP socket
"""
from __future__ import print_function
import requests
import argparse
import json
import time
from math import floor
import socket
import serial
import sys
import subprocess
import os
def get_data(url, stderr=False):
try:
r = requests.get(url, timeout=0.2)
except requests.exceptions.RequestException as exc:
if stderr:
print("Exception occured {}".format(exc))
return None
if r.status_code != requests.codes.ok:
if stderr:
print("Got error {}: {}".format(r.status_code, r.text))
return None
return r.json()
def get_global_position(base_url):
return get_data("{}/api/v1/position/global".format(base_url))
def get_master_position(base_url):
return get_data("{}/api/v1/position/master".format(base_url))
def gen_gga(time_t, lat, lng, fix_quality, num_sats, hdop, alt_m, geoidal_sep_m, dgps_age_sec=None, dgps_ref_id=None):
# Code is adapted from https://gist.github.com/JoshuaGross/d39fd69b1c17926a44464cb25b0f9828
hhmmssss = '%02d%02d%02d%s' % (time_t.tm_hour, time_t.tm_min, time_t.tm_sec, '.%02d' if 0 != 0 else '')
lat_abs = abs(lat)
lat_deg = lat_abs
lat_min = (lat_abs - floor(lat_deg)) * 60
lat_sec = round((lat_min - floor(lat_min)) * 1000)
lat_pole_prime = 'S' if lat < 0 else 'N'
lat_format = '%02d%02d.%03d' % (lat_deg, lat_min, lat_sec)
lng_abs = abs(lng)
lng_deg = lng_abs
lng_min = (lng_abs - floor(lng_deg)) * 60
lng_sec = round((lng_min - floor(lng_min)) * 1000)
lng_pole_prime = 'W' if lng < 0 else 'E'
lng_format = '%03d%02d.%03d' % (lng_deg, lng_min, lng_sec)
dgps_format = '%s,%s' % ('%.1f' % dgps_age_sec if dgps_age_sec is not None else '', '%04d' % dgps_ref_id if dgps_ref_id is not None else '')
result = 'GPGGA,%s,%s,%s,%s,%s,%d,%02d,%.1f,%.1f,M,%.1f,M,%s' % (hhmmssss, lat_format, lat_pole_prime, lng_format, lng_pole_prime, fix_quality, num_sats, hdop, alt_m, geoidal_sep_m, dgps_format)
crc = 0
for c in result:
crc = crc ^ ord(c)
crc = crc & 0xFF
return '$%s*%0.2X' % (result, crc)
def send_udp(sock, ip, port, message):
sock.sendto(message, (ip, port))
#Create a virtual port in the computer. Valid for linux with socat installed.
class VirtualPort:
def __init__(self, password, origin='/dev/ttyS8', end='/dev/ttyS9'):
self.origin = origin
self.end=end
self.p = subprocess.Popen(['/bin/bash', '-c', 'echo %s|sudo -S sudo socat PTY,link=%s PTY,link=%s' % (password, self.origin, self.end)], preexec_fn=os.setpgrp)
time.sleep(1) #Wait for process to start
subprocess.call(['/bin/bash', '-c', 'echo %s|sudo -S sudo chmod 666 %s' % (password, self.origin)])
subprocess.call(['/bin/bash', '-c', 'echo %s|sudo -S sudo chmod 666 %s' % (password, self.end)])
return
def stop(self):
os.killpg(self.p.pid, signal.SIGTERM)
return
def write(self, message):
message = "echo \"" + message + "\" > " + self.origin
subprocess.call(["/bin/bash", "-c", message])
return
def main():
parser = argparse.ArgumentParser(description=__doc__)
parser.add_argument('-u', '--url', help='IP/URL of Underwater GPS kit. Typically http://192.168.2.94', type=str, default='http://demo.waterlinked.com')
parser.add_argument('-m', '--master', help='Print master position insstead of global', action="store_true")
parser.add_argument("-v", "--verbose", help="Print NMEA sentences", action="store_true")
# UDP options
parser.add_argument('-i', '--ip', help="Enable UDP output by specifying IP address to send UDP packets. Default disabled", type=str, default='')
parser.add_argument('-p', '--port', help="Port to send UDP packet", type=int, default=5000)
# Serial port options
parser.add_argument('-s', '--serial', help="Enable serial port output by specifying port to use. Example: '/dev/ttyUSB0' or 'COM1' Default disabled", type=str, default='')
parser.add_argument('-b', '--baud', help="Serial port baud rate", type=int, default=9600)
#Virtual port options
parser.add_argument('-w', '--password', help='Password to execute sudo commands', type=str, default='')
parser.add_argument('-o', '--origin', help='Virtual port to write in', type=str, default='/dev/ttyS7')
parser.add_argument('-e', '--end', help='Virtual port where to read from', type=str, default='/dev/ttyS9')
args = parser.parse_args()
if not (args.ip or args.serial or args.password):
parser.print_help()
print("ERROR: Please specify either serial port to use, ip address to use or a password to create a virtual port")
sys.exit(1)
print("Using base_url: {}".format(args.url))
ser = None
if args.serial:
print("Serial port: {}".format(args.serial))
ser = serial.Serial(args.serial, args.baud)
sock = None
if args.ip:
print("UDP: {} {}".format(args.ip, args.port))
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
virtualPort = None
if args.password:
print("Sending data from virtual port '{}' to '{}'".format(args.origin, args.end))
virtualPort = VirtualPort(args.password, args.origin, args.end)
while True:
if args.master:
pos = get_master_position(args.url)
else:
pos = get_global_position(args.url)
if pos:
#print("Current global position lat:{} lon:{}".format(pos["lat"], pos["lon"]))
sentence = gen_gga(time.gmtime(), pos["lat"], pos["lon"], 1, 0, 0, 0, 0) #added 1 argument to fixed quality or position was rejected by other software
if args.verbose:
print(sentence)
if sock:
send_udp(sock, args.ip, args.port, sentence)
if ser:
ser.write(sentence + "\n")
if virtualPort:
#Add \ to make the simbol $ writable
dollar_sentence = '\\' + sentence
virtualPort.write(dollar_sentence)
time.sleep(0.2)
if __name__ == "__main__":
main()
More specifically responding to your question, to create a virtual port I used socat.
To install it in linux write in a terminal:
$ sudo apt-get update && sudo apt-get install socat
And after to create two connected virtual ports write:
$ sudo socat PTY PTY
You can check the creation of two virtual ports by running from another terminal:
$ ls /dev/pts*
Before and after executing socat. You will see the apparition of two ports, in my case 4 and 18:
My app only reads from ttyS_X ports so I created a link with:
$ sudo socat PTY,link=/dev/ttyS8 PTY,link=/dev/ttyS9
Finally you have to edit permissions to write and read in the ports so run from a second terminal:
$ sudo chmod 666 /dev/ttyS8
$ sudo chmod 666 /dev/ttyS9
You can check the communication by writing on this second terminal:
$ cat < /dev/ttyS9
and on a third new one:
$ echo "Hello World" > /dev/ttyS8
Note: this is also necessary even if you do not create the link. If you use the pts/X ports you also have to edit permisions to write or read:
$ sudo chmod 666 /dev/pts/18
$ sudo chmod 666 /dev/pts/4
Note2: You must keep open the socat terminal to maintain communication. When you close it or press ctrl+c the process is interrupted and the virtual ports destroyed.
Regards,
Alex
