From: drowe67 <drowe67@01035d8c-6547-0410-b346-abe4f91aad63>
Date: Tue, 6 Mar 2018 21:33:09 +0000 (+0000)
Subject: added some cmd line options and examples, getting reas repatability across gqrx and... 
X-Git-Url: http://git.whiteaudio.com/gitweb/?a=commitdiff_plain;h=76372dde9f483b0791a1ed0a1848015dc3df8b5b;p=freetel-svn-tracking.git

added some cmd line options and examples, getting reas repatability across gqrx and cmd line methods

git-svn-id: https://svn.code.sf.net/p/freetel/code@3405 01035d8c-6547-0410-b346-abe4f91aad63
---

diff --git a/codec2-dev/octave/nf_from_stdio.m b/codec2-dev/octave/nf_from_stdio.m
index fb58dd97..13aabf87 100644
--- a/codec2-dev/octave/nf_from_stdio.m
+++ b/codec2-dev/octave/nf_from_stdio.m
@@ -2,37 +2,103 @@
 % David Rowe Mar 2018
 
 #{
+
   Calculate NF in real time from 16 bit real samples from stdin
-#}
 
-N = 48000;
-Pin_dB = -100;
+  1/ When used with UDP feature of gqrx in USB mode:
+
+    $ nc -ul 7355 | octave --no-gui -qf nf_from_stdio.m
+
+  2/ Using command line tools:
+
+  a) Airspy:
+  
+    $ airspy_rx -a 6000000 -l 14 -m 15 -v 15 -r - -f 434.998 -b 1 | \
+      csdr convert_s16_f | csdr fir_decimate_cc 50 | csdr convert_f_s16 | \
+      octave --no-gui -qf ~/codec2-dev/octave/nf_from_stdio.m 120000 complex
+
+  a) HackRF:
+  
+    Term 1:
+
+    $ ~/codec2-dev/octave$ nc -ul 7355 | octave --no-gui -qf nf_from_stdio.m 80000 complex
+
+    Term 2:
+    
+    $ hackrf_transfer -r - -f 434995000 -s 4000000 -a 1 -p 1 -l 40 -g 32 | \
+      csdr convert_s8_f | csdr fir_decimate_cc 50 | csdr convert_f_s16 | \
+      nc localhost -u 735
+   
+  TODO:
+    [ ] work out why noise power st bounces around so much, signal power seems stable
+    [ ] reduce CPU load, in particular of plotting
+#}
 
 graphics_toolkit ("gnuplot")
 
-[s,c] = fread(stdin, N, "short");
+% command line arguments
+
+arg_list = argv ();
+if nargin == 0
+  printf("\nusage: %s FsHz [real|complex] [testToneLeveldBm]\n\n", program_name());
+  exit(0);
+end
+
+Fs = str2num(arg_list{1});
+shorts_per_sample = 1;
+
+if nargin == 2
+  if strcmp(arg_list{2}, "real")
+    shorts_per_sample = 1;
+  end
+  if strcmp(arg_list{2}, "complex")
+    shorts_per_sample = 2;
+  end
+end
+  
+Pin_dB = -100; % level of input test tone
+if nargin == 3
+  Pin_dB = str2num(arg_list{3});
+end
+
+printf("Fs: %d shorts_per_sample: %d Pin_dB: %f\n", Fs, shorts_per_sample, Pin_dB);
+
+[s,c] = fread(stdin, shorts_per_sample*Fs, "short");
 
 while c
-  S = fft(s.*hanning(N));
+  if shorts_per_sample == 2
+    s = s(1:2:end)+j*s(2:2:end);
+  end
+  S = fft(s.*hanning(Fs));
   SdB = 20*log10(abs(S));
-  figure(1); plot(real(s)); axis([0 N -3E4 3E4]);
+  figure(1); plot(real(s)); axis([0 Fs -3E4 3E4]);
   figure(2); plot(SdB); axis([0 12000 40 160]);
 
   % assume sine wave is between 2000 and 4000 Hz, and dominates energy in that
   % region.  Noise is between 5000 - 10000 Hz
   
-  sig_st = 2000; sig_en = 4000;
-  noise_st = 5000; noise_en = 10000;
+  sig_st = 2000; sig_en = 5000;
+  noise_st = 6000; noise_en = 10000;
+
+  % find peak and sum power a few bins either side, this ensure we don't capture
+  % too much noise as well
+  
+  [pk pk_pos] = max(abs(S));
+  if pk_pos > 5
+    Pout_dB1 = 10*log10(sum(abs(S(pk_pos-5:pk_pos+5)).^2));     % Rx output power with test signal
+  else
+    Pout_dB1 = 0;
+  end
   
-  Pout_dB = 10*log10(var(S(sig_st:sig_en)));      % Rx output power with test signal
-  G_dB    = Pout_dB - Pin_dB;                     % Gain of Rx                           
-  Nout_dB = 10*log10(var(S(noise_st:noise_en)));  % Rx output power with noise
-  Nin_dB  = Nout_dB - G_dB;                       % Rx input power with noise
-  No_dB   = Nin_dB - 10*log10(noise_en-noise_st); % Rx input power with noise in 1Hz bandwidth
-  NF_dB   = No_dB + 174;                          % compare to thermal noise to get NF
-  printf("Pout: %4.1f  Nout: %4.1f G: %4.1f  No: %4.1f NF: %3.1f dB\n", Pout_dB, Nout_dB, G_dB, No_dB, NF_dB);
+  Pout_dB = 10*log10(sum(abs(S(sig_st:sig_en)).^2));      % Rx output power with test signal
+  G_dB    = Pout_dB - Pin_dB;                             % Gain of Rx                           
+  Nout_dB = 10*log10(sum(abs(S(noise_st:noise_en)).^2)/(noise_en-noise_st));  % Rx output power with noise 
+  Nin_dB  = Nout_dB - G_dB;                               % Rx input power with noise
+  No_dB   = Nin_dB; %- 10*log10(noise_en-noise_st);       % Rx input power with noise in 1Hz bandwidth
+  NF_dB   = No_dB + 174;                                  % compare to thermal noise to get NF
+  printf("Pout: %4.1f  %d %4.1f Nout: %4.1f G: %4.1f  No: %4.1f NF: %3.1f dB\n", Pout_dB, pk_pos, Pout_dB1, Nout_dB, G_dB, No_dB, NF_dB);
 
   pause(2);
-  [s,c] = fread(stdin, N, "short");
+  [s,c] = fread(stdin, shorts_per_sample*Fs, "short");
 endwhile