% file: com8001r3.M
% modified: 9-3-02
% Author: MSS/Alain Zarembowitch
% 
%--------------------
% Generates baseband signal for the COM-8001 pattern generator
% Format is 2 (complex) * 10-bit (unsigned).
% Generate one sinewave and a QPSK modulated signal at frequency reference fc1 and fc2 respectively.
%--------------------
fs = 120000;			   % sampling rate 200 KHz typ.
nsamples = 400;	   % simulation duration, expressed as number of complex samples
nsamplespersymbol = 16;	% number of samples/symbol. sets the symbol rate = fs/nsamplespersymbol.
fc1 = 10000;				% sinewave1 in Hz
fc2 = 20000;			         % modulated signal center frequency in Hz
gain1 = 0.7				   % amplitude scaling factor 
gain2 = 0.7				   % amplitude scaling factor 


% for long simulations, store results in output file
[fid_o1,message]  = fopen('com8001r3.bin','w');
if(fid_o1 == -1)
   message
end


% initialization
last_i = 0;
last_q = 0;
current_i = 0;
current_q = 0;
b = dec2bin(0,10);
test1 = (1:nsamples);
test2 = (1:nsamples);


% synthesize square root raised cosine modulation
% 25 % rolloff, square root, (INTELSAT) 
% filter order N = 32
nfilter = 32;
symbol_rate = fs/nsamplespersymbol;
rolloff = 0.25;
coeff_txfil = Firrcos(nfilter, symbol_rate/2., rolloff, fs, 'rolloff', 'sqrt');
% store filter configuration at each sample
yii = zeros(nfilter,1);
yiq = zeros(nfilter,1);


%------------------------------------------------------
% MAIN LOOP
%------------------------------------------------------

% loop signal processing (cannot use vectors)
for j = 1:nsamples
	i = j;   
   
   % simulate the first sinewave
   phase1 = 2.*pi*fc1*(i-1)/fs;	% carrier phase
   carrier1_cos = cos(phase1);	
   carrier1_sin = sin(phase1);
   
   sigt1i = carrier1_cos*gain1;
   sigt1q = carrier1_sin*gain1;
   
   test1(i) = sigt1i;
   test2(i) = sigt1q;
   
   % simulate the second sinewave
   phase2 = 2.*pi*fc2*(i-1)/fs;	% carrier phase
   carrier2_cos = cos(phase2);	
   carrier2_sin = sin(phase2);
   
   test3(i) = carrier2_cos*gain2;
   test4(i) = carrier2_sin*gain2;
   
   % modulated 2nd carrier 
   % generate new random symbol if i = 1 modulo nsamplespersymbol
   % Generate PULSES, not square waveforms.
   if(mod(i,nsamplespersymbol) == 1) 
      bi = rand;
      if(bi > 0.5)
         ai = 1;
      else
         ai = -1;
      end
      bq = rand;
      if(bq > 0.5)
         aq = 1;
      else
         aq = -1;
      end
   else
      ai = 0;
      aq = 0;
   end  
  
   % implement transmit filtering on both in-phase and quadrature channels
   % uncomment this line
   [sigt2i, yfi] = filter(coeff_txfil, 1, ai, yii, 1);
   yii = yfi;
   [sigt2q, yfq] = filter(coeff_txfil, 1, aq, yiq, 1);
   yiq = yfq;
   
   test5(i) = sigt2i;
   test6(i) = sigt2q;
   
   
   % QPSK modulation
   sigt3i = gain2*((carrier2_cos * sigt2i) - (carrier2_sin * sigt2q));
   sigt3q = gain2*((carrier2_sin * sigt2i) + (carrier2_cos * sigt2q));

   test7(i) = sigt3i;
   test8(i) = sigt3q;
   
   
   % sum both signals. Scale to prevent overflow
   sigt4i = (sigt1i + sigt3i)/2.;
   sigt4q = (sigt1q + sigt3q)/2.;
   
   test9(i) = sigt4i;
   test10(i) = sigt4q;
   
   
   % convert samples to 10-bit unsigned format
   sigt4i = min(max((floor((sigt4i+1.)*511.5)),0.),1023);
   sigt4q = min(max((floor((sigt4q+1.)*511.5)),0.),1023);
   
   %invert bit order because of pinout
   a = dec2bin(sigt4i, 10);
   b(1) = a(10);
   b(2) = a(9);
   b(3) = a(8);
   b(4) = a(7);
   b(5) = a(6);
   b(6) = a(5);
   b(7) = a(4);
   b(8) = a(3);
   b(9) = a(2);
   b(10) = a(1);
   outputi = bin2dec(b);
   
   a = dec2bin(sigt4q, 10);
   b(1) = a(10);
   b(2) = a(9);
   b(3) = a(8);
   b(4) = a(7);
   b(5) = a(6);
   b(6) = a(5);
   b(7) = a(4);
   b(8) = a(3);
   b(9) = a(2);
   b(10) = a(1);
   outputq = bin2dec(b);
   
   
   % pack samples into byte-size format
   % wait until two complex samples are collected before writing into file (makes it easier to 
   % manage the byte alignments): 4 * 10-bits is a multiple of 8.
   if(mod(j,2) == 0)
      % even sample
      current_i = outputi;
      current_q = outputq;
      
      a = bitand(bitshift(last_q,-2), 255);
	   fprintf(fid_o1,'%c',a);
      a = bitand(bitor(bitshift(last_q,6),bitshift(last_i,-4)),255);
      fprintf(fid_o1,'%c',a);
      a = bitand(bitor(bitshift(last_i,4),bitshift(current_q,-6)),255);
      fprintf(fid_o1,'%c',a);
      a = bitand(bitor(bitshift(current_q,2),bitshift(current_i,-8)),255);
      fprintf(fid_o1,'%c',a);
      a = bitand(current_i,255);
      fprintf(fid_o1,'%c',a);
      
      % keep track of simulation progress
      if(mod(j,10000) == 0)
         j/10000
     	end;
      
   else
      % odd sample
	   % remember last sample
      last_i = outputi;
      last_q = outputq;
   end;
  
   
 end   

  subplot(5,1,1);
  title('first sine');
  plot(test1);
  hold on;
  plot(test2,'r');
  ylabel('')
  
  subplot(5,1,2);
  title('second sine');
  plot(test3);
  hold on;
  plot(test4,'r');
  ylabel('')
  
  subplot(5,1,3);
  title('modulated second signal');
  plot(test5);
  hold on;
  plot(test6,'r');
  ylabel('')

  subplot(5,1,4);
  title('QPSK modulation');
  plot(test7);
  hold on;
  plot(test8,'r');
  ylabel('')
  
  subplot(5,1,5);
  title('sum of first signal and QPSK modulated second signal');
  plot(test9);
  hold on;
  plot(test10,'r');
  xlabel('');
  ylabel('')

% close opened files
fclose(fid_o1);