Started model FSK to be ported to C

git-svn-id: https://svn.code.sf.net/p/freetel/code@2475 01035d8c-6547-0410-b346-abe4f91aad63

diff --git a/codec2-dev/octave/ya_fsk.m b/codec2-dev/octave/ya_fsk.m
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+% yafsk.m
+% Yet-another-FSK
+% Brady O'Brien 20 October 2015
+%
+% This is a model for the first attempt at a C FSK modem. Based on fsk_horus and maybe a little fsk4.
+% First revision will just be 2fsk
+% [x] - Modem init and struct def
+% [x] - Direct SDR modulator, probably not FM based
+% [.] - Direct SDR non-coherent demodulator
+%    [ ] - Core demodulation routine
+%    [ ] - Timing offset estimation
+%    [ ] - Freq. offset estimation
+%    [ ] - Bit slip, maybe
+% [ ] - The C port
+% [ ] - Some stuff to verify the C port
+
+%clear all;
+fm
+
+%Basic parameters for a simple FSK modem
+fsk_setup_info.Rs = 2400;  % Symbol rate
+fsk_setup_info.nfsk = 2;      % Number of unique symbols. Must be 2.
+fsk_setup_info.Fs = 48000; % Sample frequency
+fsk_setup_info.Fsym = fsk_setup_info.Rs; %Symbol spacing
+fsk_setup_info.txmap = @(bits) bits+1; %Map TX bits to 2fsk symbols
+fsk_setup_info.rxmap = @(syms) syms==2; %Map 2fsk RX symbols to bits
+
+
+function states = yafsk_init(fsk_config)
+  Fs = states.Fs = fsk_config.Fs;
+  Rs = states.Rs = fsk_config.Rs;
+  nfsk = states.nfsk = fsk_config.nfsk;
+  Ts = states.Ts = Fs/Rs;
+  Fsym = states.Fsym = fsk_config.Fsym;
+  states.config = fsk_config;
+
+  if nfsk != 2
+    error("Gotta be 2fsk")
+  endif
+ 
+  %Symbol frequencies. Fixed to intervals of Fsym.
+  states.fsyms = [-(Fsym/2) (Fsym/2)];
+  states.tx_phase = 0;
+endfunction
+
+function tx = yafsk_mod(states,bits)
+  Ts = states.Ts;
+  Fs = states.Fs;
+  fsyms = states.fsyms;
+  tx_phase = states.tx_phase;
+  %Map bits into symbols
+  syms = states.config.txmap(bits);
+  tx = zeros(1,Ts*length(syms));
+  
+  for ii = (1:length(syms))
+    cur_sym_f = fsyms(syms(ii));
+    for jj = (1:Ts)
+        tx_phase = tx_phase + jj*2*pi*cur_sym_f/Fs;
+        tx(ii+jj) = exp(j*tx_phase)
+    end
+
+    %Correct phase
+    if(tx_phase > 2*pi)
+        tx_phase = tx_phase - 2*pi;
+    elseif(tx_phase < -2*pi);
+        tx_phase = tx_phase + 2*pi
+    endif
+  end
+  states.tx_phase = tx_phase;
+endfunction
+
+function bits = yafsk_demod(states,stream)
+  
+endfunction
+
+
+
+
+