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[Discuss-gnuradio] About receiver physical layer of Benchmark

From: Hassaan Ajaz
Subject: [Discuss-gnuradio] About receiver physical layer of Benchmark
Date: Mon, 26 Apr 2010 22:59:38 +0500

I am basically trying to develop a Cooperative MIMO test-bed.
So my problem is regarding the physical layer of benchmark for gmsk
The basic flow graph of benchmark for receiver is
USRP--->Channel Filter--->Quadrature Demod--->Clock recovery--->Slicer--->Correlator--->Framer sink

Now what I am trying to do is to put a msg sink after the clock recovery block in the file pkt.py by first removing slicer from gmsk.py and then adding the following code in pkt.py

PROBLEM WITH CODE:The code does not show any syntax errors but it does not receive anything at all. Kindly help.

class demod_pkts(gr.hier_block2):
    Wrap an arbitrary digital demodulator in our packet handling framework.

    The input is complex baseband.  When packets are demodulated, they are passed to the
    app via the callback.

    def __init__(self, demodulator, access_code=None, callback=None, threshold=-1):
    Hierarchical block for demodulating and deframing packets.

    The input is the complex modulated signal at baseband.
        Demodulated packets are sent to the handler.

        @param demodulator: instance of demodulator class (gr_block or hier_block2)
        @type demodulator: complex baseband in
        @param access_code: AKA sync vector
        @type access_code: string of 1's and 0's
        @param callback:  function of two args: ok, payload
        @type callback: ok: bool; payload: string
        @param threshold: detect access_code with up to threshold bits wrong (-1 -> use default)
        @type threshold: int

    gr.hier_block2.__init__(self, "demod_pkts",
                gr.io_signature(1, 1, gr.sizeof_gr_complex), # Input signature
                gr.io_signature(0, 0, 0))                    # Output signature

        self._demodulator = demodulator
        if access_code is None:
            access_code = packet_utils.default_access_code
        if not packet_utils.is_1_0_string(access_code):
            raise ValueError, "Invalid access_code %r. Must be string of 1's and 0's" % (access_code,)
        self._access_code = access_code

        if threshold == -1:
            threshold = 12              # FIXME raise exception

        self._rcvd_pktq = gr.msg_queue()          # holds packets from the PHY
        self._msg_sink=gr.message_sink(gr.sizeof_float,self._rcvd_pktq,True) #have tried with both Dont_block true and false. No effect
        #self.framer_sink = gr.framer_sink_1(self._rcvd_pktq)
        self.connect(self, self._demodulator, self._msg_sink)    #HERE I have removed the access correlator onwards connection
        self._watcher = _queue_watcher_thread(self._rcvd_pktq, callback)     #the received queue is then sent to the class queue watcher

class _queue_watcher_thread(_threading.Thread):
    def __init__(self, rcvd_pktq, callback):
        self.rcvd_pktq = rcvd_pktq
        self.callback = callback
    self.keep_running = True
        self._combine=combiner(self.callback)  #class defined after next few lines

    def run(self):
        while self.keep_running:
            msg = self.rcvd_pktq.delete_head()
            #ok, payload = packet_utils.unmake_packet(msg.to_string(), int(msg.arg1()))
            self._combine.proc_pkt(msg)            #here i have called the function that inserts the FLOAT msg into the msg source queue in the class combiner

class combiner(gr.hier_block2):
    def __init__(self,callback):
    gr.hier_block2.__init__(self, "combiner",
                gr.io_signature(0, 0, 0),                    # Input signature
                gr.io_signature(0, 0, 0)) # Output signature

        self.call = callback
        self.slicer = gr.binary_slicer_fb()
        self.framer_sink = gr.framer_sink_1(self.msgqq)
        self.correlator = gr.correlate_access_code_bb(packet_utils.default_access_code, 12)
        self.connect(self.msgsrc, self.slicer, self.correlator,self.framer_sink)   #this is the source where i inserted the msg and the connection with remaining modules

    def proc_pkt(self, msge):

class _que_watcher_thread(_threading.Thread):
    def __init__(self, rcvd_pktq, callback):
        self.rcvd_pktq = rcvd_pktq
        self.callback = callback
        self.keep_running = True

    def run(self):
        while self.keep_running:
            msg = self.rcvd_pktq.delete_head()
            ok, payload = packet_utils.unmake_packet(msg.to_string(), int(msg.arg1()))
            if self.callback:
                self.callback(ok, payload)

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