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#!/usr/bin/env python2
# -*- coding: utf-8 -*-
# Virtual Um-interface (fake transceiver)
# Simple TDMA frame clock generator
#
# (C) 2017 by Vadim Yanitskiy <axilirator@gmail.com>
#
# All Rights Reserved
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
import signal
import time
import sys
from threading import Timer
from udp_link import UDPLink
COPYRIGHT = \
"Copyright (C) 2017 by Vadim Yanitskiy <axilirator@gmail.com>\n" \
"License GPLv2+: GNU GPL version 2 or later " \
"<http://gnu.org/licenses/gpl.html>\n" \
"This is free software: you are free to change and redistribute it.\n" \
"There is NO WARRANTY, to the extent permitted by law.\n"
class CLCKGen:
# GSM TDMA definitions
SEC_DELAY_US = 1000 * 1000
GSM_SUPERFRAME = 2715648
GSM_FRAME_US = 4615.0
# Average loop back delay
LO_DELAY_US = 90.0
# State variables
timer = None
def __init__(self, clck_links, clck_start = 0, ind_period = 102):
self.clck_links = clck_links
self.ind_period = ind_period
self.clck_src = clck_start
# Calculate counter time
self.ctr_interval = self.GSM_FRAME_US - self.LO_DELAY_US
self.ctr_interval /= self.SEC_DELAY_US
self.ctr_interval *= self.ind_period
def start(self):
# Send the first indication
self.send_clck_ind()
def stop(self):
# Stop pending timer
if self.timer is not None:
self.timer.cancel()
self.timer = None
def send_clck_ind(self):
# Keep clock cycle
if self.clck_src % self.GSM_SUPERFRAME >= 0:
self.clck_src %= self.GSM_SUPERFRAME
# We don't need to send so often
if self.clck_src % self.ind_period == 0:
# Create UDP payload
payload = "IND CLOCK %u\0" % self.clck_src
# Send indication to all UDP links
for link in self.clck_links:
link.send(payload)
# Debug print
print("[T] %s" % payload)
# Increase frame count
self.clck_src += self.ind_period
# Schedule a new indication
self.timer = Timer(self.ctr_interval, self.send_clck_ind)
self.timer.start()
# Just a wrapper for independent usage
class Application:
def __init__(self):
# Set up signal handlers
signal.signal(signal.SIGINT, self.sig_handler)
# Print copyright
print(COPYRIGHT)
def run(self):
self.link = UDPLink("127.0.0.1", 5800, 5700)
self.clck = CLCKGen([self.link], ind_period = 51)
self.clck.start()
def sig_handler(self, signum, frame):
print("Signal %d received" % signum)
if signum is signal.SIGINT:
self.clck.stop()
self.link.shutdown()
if __name__ == '__main__':
app = Application()
app.run()
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