diff --git a/python/trx/radio_if.py b/python/trx/radio_if.py
index 689f074..9e97277 100644
--- a/python/trx/radio_if.py
+++ b/python/trx/radio_if.py
@@ -2,9 +2,10 @@
 # -*- coding: utf-8 -*-
 
 # GR-GSM based transceiver
-# Follow graph implementation
+# Extending a GRC flowgraph gr-gsm/examples/trx_radio_if/radio_if_grc.grc
 #
 # (C) 2016-2017 by Vadim Yanitskiy <axilirator@gmail.com>
+# (C) 2017      by Piotr Krysik <ptrkrysik@gmail.com>
 #
 # All Rights Reserved
 #
@@ -22,229 +23,37 @@
 # with this program; if not, write to the Free Software Foundation, Inc.,
 # 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 
-import pmt
-import time
-import grgsm
-import osmosdr
+from grgsm.trx import radio_if_grc
 
-from math import pi
-
-from gnuradio.filter import firdes
-from gnuradio import digital
-from gnuradio import blocks
-from gnuradio import uhd
-from gnuradio import gr
-
-
-# HACK: should be implemented in C++!
-import numpy as np
-
-class burst_type_filter(gr.sync_block):
-    def __init__(self, burst_types=[]):
-        gr.sync_block.__init__(
-            self,
-            name='Burst type filter',
-            in_sig=[],
-            out_sig=[]
-        )
-        self.burst_types = burst_types
-        self.message_port_register_in(pmt.intern("bursts_in"))
-        self.message_port_register_out(pmt.intern("bursts_out"))
-        self.set_msg_handler(pmt.intern("bursts_in"), self.filter)
-
-    def filter(self, msg):
-        burst_with_header = pmt.to_python(pmt.cdr(msg))
-        burst = burst_with_header[-148:]
-        header = np.ndarray.tolist(burst_with_header[0:-148])
-        burst_type = header[12]
-        if burst_type in self.burst_types:
-            self.message_port_pub(pmt.intern("bursts_out"), msg)
-
-class burst_to_fn_time(gr.basic_block):
-    def __init__(self):  # only default arguments here
-        gr.basic_block.__init__(
-            self,
-            name='Burst to fn_time',
-            in_sig=[],
-            out_sig=[]
-        )
-        self.message_port_register_in(pmt.intern("bursts_in"))
-        self.message_port_register_out(pmt.intern("fn_time_out"))
-        self.set_msg_handler(pmt.intern("bursts_in"), self.convert)
-
-    def convert(self, msg):
-        fn_time = pmt.dict_ref(pmt.car(msg),pmt.intern("fn_time"),pmt.PMT_NIL)
-        fn_time_msg = pmt.dict_add(pmt.make_dict(), pmt.intern("fn_time"), fn_time)
-        if pmt.to_python(fn_time) is not None:
-            self.message_port_pub(pmt.intern("fn_time_out"), fn_time_msg)
-
-class radio_if(gr.top_block):
-	# PHY specific variables
-	rx_freq = 935e6
-	tx_freq = 890e6
-
+class radio_if(radio_if_grc):
 	# Application state flags
 	trx_started = False
 
-	# GSM timings
-	delay_correction = 285.616e-6
-	ul_dl_shift = -(6.0/1625000*(156.25)*3)
-
 	def __init__(self, phy_args, phy_sample_rate,
 			phy_rx_gain, phy_tx_gain, phy_ppm,
 			phy_rx_antenna, phy_tx_antenna,
-			trx_remote_addr, trx_base_port):
+			trx_remote_addr, trx_base_port,
+			phy_tx_freq=938900000,
+			phy_rx_freq=938900000-45e6,
+			delay_correction=285.616e-6,
+			uplink_shift=-(6.0/1625000*(156.25)*3),
+			timing_advance=0):
 
 		print("[i] Init Radio interface")
 
-		# PHY specific variables
-		self.rx_gain = phy_rx_gain
-		self.tx_gain = phy_tx_gain
-
-		gr.top_block.__init__(self, "GR-GSM TRX")
-
-		# TRX Burst Interface
-		self.trx_burst_if = grgsm.trx_burst_if(
-			trx_remote_addr, str(trx_base_port))
-
-
-		# RX path definition
-		self.phy_src = uhd.usrp_source(phy_args,
-			uhd.stream_args(cpu_format="fc32",
-				channels=range(1)))
-
-		self.phy_src.set_center_freq(self.rx_freq, 0)
-		self.phy_src.set_antenna(phy_rx_antenna, 0)
-		self.phy_src.set_samp_rate(phy_sample_rate)
-		self.phy_src.set_bandwidth(650e3, 0)
-		self.phy_src.set_gain(phy_rx_gain)
-
-		self.gsm_input = grgsm.gsm_input(
-			ppm = phy_ppm - int(phy_ppm), osr = 4,
-			fc = self.rx_freq, samp_rate_in = phy_sample_rate)
-
-		self.gsm_receiver = grgsm.receiver(4, ([0]), ([]))
-
-		self.gsm_clck_ctrl = grgsm.clock_offset_control(
-			self.rx_freq, phy_sample_rate, osr = 4)
-
-		self.ts_filter = grgsm.burst_timeslot_filter(0)
-		self.ts_filter.set_policy(grgsm.FILTER_POLICY_DROP_ALL)
-
-		# Connections
-		self.connect(
-			(self.phy_src, 0),
-			(self.gsm_input, 0))
-
-		self.connect(
-			(self.gsm_input, 0),
-			(self.gsm_receiver, 0))
-
-		self.msg_connect(
-			(self.gsm_receiver, 'C0'),
-			(self.ts_filter, 'in'))
-
-		self.msg_connect(
-			(self.ts_filter, 'out'),
-			(self.trx_burst_if, 'bursts'))
-
-		self.msg_connect(
-			(self.gsm_receiver, 'measurements'),
-			(self.gsm_clck_ctrl, 'measurements'))
-
-		self.msg_connect(
-			(self.gsm_clck_ctrl, 'ctrl'),
-			(self.gsm_input, 'ctrl_in'))
-
-
-		# TX Path Definition
-		self.phy_sink = uhd.usrp_sink(phy_args,
-			uhd.stream_args(cpu_format="fc32",
-				channels=range(1)), "packet_len")
-
-		self.phy_sink.set_antenna(phy_tx_antenna, 0)
-		self.phy_sink.set_samp_rate(phy_sample_rate)
-		self.phy_sink.set_center_freq(self.tx_freq, 0)
-		self.phy_sink.set_gain(self.tx_gain)
-
-		self.tx_time_setter = grgsm.txtime_setter(
-			0xffffffff, 0, 0, 0, 0, 0,
-			self.delay_correction + self.ul_dl_shift)
-
-		self.tx_burst_proc = grgsm.preprocess_tx_burst()
-
-		self.pdu_to_tagged_stream = blocks.pdu_to_tagged_stream(
-			blocks.byte_t, 'packet_len')
-
-		self.gmsk_mod = grgsm.gsm_gmsk_mod(
-			BT = 4, pulse_duration = 4, sps = 4)
-
-		self.burst_shaper = digital.burst_shaper_cc(
-			(firdes.window(firdes.WIN_HANN, 16, 0)),
-			0, 20, False, "packet_len")
-
-		# Connections
-		self.msg_connect(
-			(self.trx_burst_if, 'bursts'),
-			(self.tx_time_setter, 'bursts_in'))
-
-		self.msg_connect(
-			(self.tx_time_setter, 'bursts_out'),
-			(self.tx_burst_proc, 'bursts_in'))
-
-		self.msg_connect(
-			(self.tx_burst_proc, 'bursts_out'),
-			(self.pdu_to_tagged_stream, 'pdus'))
-
-		self.connect(
-			(self.pdu_to_tagged_stream, 0),
-			(self.gmsk_mod, 0))
-
-		self.connect(
-			(self.gmsk_mod, 0),
-			(self.burst_shaper, 0))
-
-		self.connect(
-			(self.burst_shaper, 0),
-			(self.phy_sink, 0))
-
-
-		# RX & TX synchronization
-		self.bt_filter = burst_type_filter([3])
-		self.burst_to_fn_time = burst_to_fn_time()
-
-		# Connections
-		self.msg_connect(
-			(self.gsm_receiver, 'C0'),
-			(self.bt_filter, 'bursts_in'))
-
-		self.msg_connect(
-			(self.bt_filter, 'bursts_out'),
-			(self.burst_to_fn_time, 'bursts_in'))
-
-		self.msg_connect(
-			(self.burst_to_fn_time, 'fn_time_out'),
-			(self.tx_time_setter, 'fn_time'))
+		radio_if_grc.__init__(self,
+			samp_rate=phy_sample_rate, 
+			tx_gain=phy_tx_gain, rx_gain=phy_rx_gain,
+			tx_freq=phy_tx_freq, rx_freq=phy_rx_freq,
+			osr=4, ppm=phy_ppm, 
+			trx_base_port=str(trx_base_port),
+			trx_remote_addr=trx_remote_addr,
+			delay_correction=delay_correction,
+			uplink_shift=uplink_shift,
+			timing_advance=timing_advance)
 
 	def shutdown(self):
 		print("[i] Shutdown Radio interface")
 		self.stop()
 		self.wait()
 
-	def set_rx_freq(self, fc):
-		self.phy_src.set_center_freq(fc, 0)
-		self.gsm_clck_ctrl.set_fc(fc)
-		self.gsm_input.set_fc(fc)
-		self.rx_freq = fc
-
-	def set_tx_freq(self, fc):
-		self.phy_sink.set_center_freq(fc, 0)
-		self.tx_freq = fc
-
-	def set_rx_gain(self, gain):
-		self.phy_src.set_gain(gain, 0)
-		self.rx_gain = gain
-
-	def set_tx_gain(self, gain):
-		self.phy_sink.set_gain(gain, 0)
-		self.tx_gain = gain