ov_dummy_device.py

"""
Reads GPS data from gpsfeed+ (https://sourceforge.net/projects/gpsfeed/), adds
some fake FLARM and OpenVario data and sends this on to XCSoar.
"""

import socket
import functools
import time
import datetime as dt


XCSOAR_PORT = 4353
GPSFEED_PORT = 2222


def calculate_nmea_checksum(raw_sentence):
    return (
        "%0.2X" %
        functools.reduce(lambda a, b: a ^ b, (ord(char) for char in raw_sentence))
    )

def flarm_stat(**kw):
    yield "PFLAU,1,1,1,1,2,-30,2,-32,300"

def flarm_target(**kw):
    lines = """
    PFLAA,0,-315,338,235,2,DDD335,201,,33,0.6,1
    PFLAA,0,-253,442,398,2,DDC194,195,,38,1.2,1
    PFLAA,0,-392,-6,326,2,DDAECF,294,,32,0.4,1
    PFLAA,0,-237,-70,315,2,DD8403,337,,24,2.3,1
    PFLAA,0,-435,238,229,2,DDAF22,228,,31,-1.8,1
    PFLAA,0,-1533,451,39,2,DDDC55,325,,27,-2.2,1
    PFLAA,0,-51,-68,328,2,DD94C2,21,,25,2.5,1
    PFLAA,0,-120,386,405,2,DDD8E9,142,,33,0.2,1
    PFLAU,6,1,2,1,0,144,0,235,446
    """
    for line in lines.splitlines():
        line = line.strip()
        if line:
            yield line


def ov_vario(**kw):
    yield "POV,E,+1.00"

def ov_alt_ias(**kw):
    yield "POV,P,1000.00,Q,40.00"

def format_nmea_msg(raw_sentence):
    return "${}*{}".format(raw_sentence, calculate_nmea_checksum(raw_sentence))


def main():
    xconn = None
    feedconn = None
    buffers = ""

    while True:
        if not xconn:
            try:
                xconn = socket.create_connection(('127.0.0.1', XCSOAR_PORT))
            except Exception as exc:
                print("failed to connect to XCSoar", exc)

        if not feedconn:
            try:
                # run gpsfeed+ somewhere (you can also run it on your PC if your OV device has network access)
                feedconn = socket.create_connection(('127.0.0.1', GPSFEED_PORT))
            except Exception as exc:
                print("failed to connect to gpsfeed", exc)

        try:
            if feedconn:
                buff = feedconn.recv(4096)
                if buffers:
                    buff = buffers + buff
                    buffers = ""
                buff_lines = buff.splitlines()
                for line in buff.splitlines(True):
                    if line.endswith("\r\n"):
                        buff_lines.append(line.strip())
                    else:  # only the last "line"
                        buffers = buffers + line

                if xconn:
                    for line in buff_lines:
                        xconn.send((line + "\r\n").encode())

                    #for msg_factory in [flarm_stat, flarm_target, ov_vario, ov_alt_ias]:
                    for msg_factory in [flarm_target]:
                        for msg in msg_factory():
                            xconn.send((format_nmea_msg(msg) + "\r\n").encode())
            time.sleep(0.1)
        except Exception as exc:
            print("send failed", exc)
            xconn = None
            feedconn = None
            buffers = ""

if __name__ == "__main__":
    main()