usrp_nbfm_ptt.py

这是用python语言写的一个数字广播的信号处理工具包。利用它

        # print "key_down:", evt.m_keyCode
        if evt.m_keyCode == wx.WXK_SPACE and not(self.space_bar_pressed):
            self.space_bar_pressed = True
            self.set_transmit(True)

    def _on_key_up(self, evt):
        # print "key_up", evt.m_keyCode
        if evt.m_keyCode == wx.WXK_SPACE:
            self.space_bar_pressed = False
            self.set_transmit(False)

    def _on_kill_focus(self, evt):
        # if we lose the keyboard focus, turn off the transmitter
        self.space_bar_pressed = False
        self.set_transmit(False)
        

# ////////////////////////////////////////////////////////////////////////
#                           Transmit Path
# ////////////////////////////////////////////////////////////////////////

class transmit_path(gr.hier_block2):
    def __init__(self, subdev_spec, audio_input):
	gr.hier_block2.__init__(self, "transmit_path",
				gr.io_signature(0, 0, 0), # Input signature
				gr.io_signature(0, 0, 0)) # Output signature
				
        self.u = usrp.sink_c ()

        dac_rate = self.u.dac_rate();
        self.if_rate = 320e3                               # 320 kS/s
        self.usrp_interp = int(dac_rate // self.if_rate)
        self.u.set_interp_rate(self.usrp_interp)
        self.sw_interp = 10
        self.audio_rate = self.if_rate // self.sw_interp   #  32 kS/s

        self.audio_gain = 10
        self.normal_gain = 32000

        self.audio = audio.source(int(self.audio_rate), audio_input)
        self.audio_amp = gr.multiply_const_ff(self.audio_gain)

        lpf = gr.firdes.low_pass (1,                # gain
                                  self.audio_rate,            # sampling rate
                                  3800,               # low pass cutoff freq
                                  300,                # width of trans. band
                                  gr.firdes.WIN_HANN) # filter type 

        hpf = gr.firdes.high_pass (1,                # gain
                                  self.audio_rate,            # sampling rate
                                  325,               # low pass cutoff freq
                                  50,                # width of trans. band
                                  gr.firdes.WIN_HANN) # filter type 

        audio_taps = convolve(array(lpf),array(hpf))
        self.audio_filt = gr.fir_filter_fff(1,audio_taps)

        self.pl = blks2.ctcss_gen_f(self.audio_rate,123.0)
        self.add_pl = gr.add_ff()
        self.connect(self.pl,(self.add_pl,1))

        self.fmtx = blks2.nbfm_tx(self.audio_rate, self.if_rate)
        self.amp = gr.multiply_const_cc (self.normal_gain)

        # determine the daughterboard subdevice we're using
        if subdev_spec is None:
            subdev_spec = usrp.pick_tx_subdevice(self.u)
        self.u.set_mux(usrp.determine_tx_mux_value(self.u, subdev_spec))
        self.subdev = usrp.selected_subdev(self.u, subdev_spec)
        print "TX using", self.subdev.name()

        self.connect(self.audio, self.audio_amp, self.audio_filt,
                     (self.add_pl,0), self.fmtx, self.amp, self.u)

        self.set_gain(self.subdev.gain_range()[1])  # set max Tx gain


    def set_freq(self, target_freq):
        """
        Set the center frequency we're interested in.

        @param target_freq: frequency in Hz
        @rypte: bool

        Tuning is a two step process.  First we ask the front-end to
        tune as close to the desired frequency as it can.  Then we use
        the result of that operation and our target_frequency to
        determine the value for the digital up converter.  Finally, we feed
        any residual_freq to the s/w freq translater.
        """
        r = self.u.tune(self.subdev._which, self.subdev, target_freq)
        if r:
            # Use residual_freq in s/w freq translator
            return True

        return False

    def set_gain(self, gain):
        self.gain = gain
        self.subdev.set_gain(gain)

    def set_enable(self, enable):
        self.subdev.set_enable(enable)            # set H/W Tx enable
        if enable:
            self.amp.set_k (self.normal_gain)
        else:
            self.amp.set_k (0)



# ////////////////////////////////////////////////////////////////////////
#                           Receive Path
# ////////////////////////////////////////////////////////////////////////

class receive_path(gr.hier_block2):
    def __init__(self, subdev_spec, gain, audio_output):
	gr.hier_block2.__init__(self, "receive_path",
				gr.io_signature(0, 0, 0), # Input signature
				gr.io_signature(0, 0, 0)) # Output signature

        self.u = usrp.source_c ()
        adc_rate = self.u.adc_rate()

        self.if_rate = 256e3                         # 256 kS/s
        usrp_decim = int(adc_rate // self.if_rate)
        if_decim = 4
        self.u.set_decim_rate(usrp_decim)
        self.quad_rate = self.if_rate // if_decim    #  64 kS/s
        audio_decim = 2
        audio_rate = self.quad_rate // audio_decim   #  32 kS/s

        if subdev_spec is None:
            subdev_spec = usrp.pick_rx_subdevice(self.u)
        self.subdev = usrp.selected_subdev(self.u, subdev_spec)
        print "RX using", self.subdev.name()

        self.u.set_mux(usrp.determine_rx_mux_value(self.u, subdev_spec))

        # Create filter to get actual channel we want
        chan_coeffs = gr.firdes.low_pass (1.0,                # gain
                                          self.if_rate,       # sampling rate
                                          13e3,               # low pass cutoff freq
                                          4e3,                # width of trans. band
                                          gr.firdes.WIN_HANN) # filter type 

        print "len(rx_chan_coeffs) =", len(chan_coeffs)

        # Decimating Channel filter with frequency translation
        # complex in and out, float taps
        self.ddc = gr.freq_xlating_fir_filter_ccf(if_decim,       # decimation rate
                                                  chan_coeffs,    # taps
                                                  0,              # frequency translation amount
                                                  self.if_rate)   # input sample rate

        # instantiate the guts of the single channel receiver
        self.fmrx = blks2.nbfm_rx(audio_rate, self.quad_rate)

        # standard squelch block
        self.squelch = blks2.standard_squelch(audio_rate)

        # audio gain / mute block
        self._audio_gain = gr.multiply_const_ff(1.0)

        # sound card as final sink
        audio_sink = audio.sink (int(audio_rate), audio_output)
        
        # now wire it all together
        self.connect (self.u, self.ddc, self.fmrx, self.squelch, self._audio_gain, audio_sink)

        if gain is None:
            # if no gain was specified, use the mid-point in dB
            g = self.subdev.gain_range()
            gain = float(g[0]+g[1])/2

        self.enabled = True
        self.set_gain(gain)
        v = self.volume_range()
        self.set_volume((v[0]+v[1])/2)
        s = self.squelch_range()
        self.set_squelch((s[0]+s[1])/2)
        
        
    def volume_range(self):
        return (-20.0, 0.0, 0.5)

    def set_volume (self, vol):
        g = self.volume_range()
        self.volume = max(g[0], min(g[1], vol))
        self._update_audio_gain()

    def set_enable(self, enable):
        self.enabled = enable
        self._update_audio_gain()

    def _update_audio_gain(self):
        if self.enabled:
            self._audio_gain.set_k(10**(self.volume/10))
        else:
            self._audio_gain.set_k(0)

    def squelch_range(self):
        return self.squelch.squelch_range()
    
    def set_squelch(self, threshold):
        print "SQL =", threshold
        self.squelch.set_threshold(threshold)

    def threshold(self):
        return self.squelch.threshold()
    
    def set_freq(self, target_freq):
        """
        Set the center frequency we're interested in.

        @param target_freq: frequency in Hz
        @rypte: bool

        Tuning is a two step process.  First we ask the front-end to
        tune as close to the desired frequency as it can.  Then we use
        the result of that operation and our target_frequency to
        determine the value for the digital down converter in the
        FPGA.  Finally, we feed any residual_freq to the s/w freq
        translator.
        """
        r = self.u.tune(0, self.subdev, target_freq)
        if r:
            # Use residual_freq in s/w freq translater
            # print "residual_freq =", r.residual_freq
            self.ddc.set_center_freq(-r.residual_freq)
            return True

        return False

    def set_gain(self, gain):
        self.gain = gain
        self.subdev.set_gain(gain)


# ////////////////////////////////////////////////////////////////////////
#                                Main
# ////////////////////////////////////////////////////////////////////////

def main():
    app = stdgui2.stdapp(ptt_block, "NBFM Push to Talk")
    app.MainLoop()

if __name__ == '__main__':
    main()