[Commit-gnuradio] gnuradio-core/src/lib/general gr_correlate_acce...

[Thomas W. Rondeau]

CVSROOT:        /sources/gnuradio
Module name:    gnuradio-core
Changes by:     Thomas W. Rondeau <trondeau1122>        06/06/29 20:26:54

Modified files:
        src/lib/general: gr_correlate_access_code_bb.cc 
                         gr_correlate_access_code_bb.h 

Log message:
        fixed branching issue and cleaned up code in 
gr_correlate_access_code_bb.cc

CVSWeb URLs:
http://cvs.savannah.gnu.org/viewcvs/gnuradio-core/src/lib/general/gr_correlate_access_code_bb.cc?cvsroot=gnuradio&r1=1.4&r2=1.5
http://cvs.savannah.gnu.org/viewcvs/gnuradio-core/src/lib/general/gr_correlate_access_code_bb.h?cvsroot=gnuradio&r1=1.2&r2=1.3

Patches:
Index: gr_correlate_access_code_bb.cc
===================================================================
RCS file: 
/sources/gnuradio/gnuradio-core/src/lib/general/gr_correlate_access_code_bb.cc,v
retrieving revision 1.4
retrieving revision 1.5
diff -u -b -r1.4 -r1.5
--- gr_correlate_access_code_bb.cc      28 Jun 2006 18:30:38 -0000      1.4
+++ gr_correlate_access_code_bb.cc      29 Jun 2006 20:26:54 -0000      1.5
@@ -45,7 +45,7 @@
                   gr_make_io_signature (1, 1, sizeof(char)),
                   gr_make_io_signature (1, 1, sizeof(char))),
     d_data_reg(0), d_flag_reg(0), d_flag_bit(0), d_mask(0),
-    d_threshold(threshold), d_rotation(0)
+    d_threshold(threshold), d_flip(0)
 
 {
   if (!set_access_code(access_code)){
@@ -71,15 +71,13 @@
 
   d_flag_bit = 1LL << (64 - len);      // Where we or-in new flag values.
                                         // new data always goes in 
0x0000000000000001
-  d_access_code[0] = 0;
+  d_access_code = 0;
   for (unsigned i=0; i < 64; i++){
-    d_access_code[0] <<= 1;
+    d_access_code <<= 1;
     if (i < len)
-      d_access_code[0] |= access_code[i] & 1;  // look at LSB only
+      d_access_code |= access_code[i] & 1;     // look at LSB only
   }
 
-  d_access_code[1] = ~d_access_code[0]; // used for non-differential BPSK
-  
   return true;
 }
 
@@ -96,43 +94,33 @@
     // compute output value
     unsigned int t = 0;
 
-    // data bit   
-    switch(d_rotation)
-    {
-      case(0):
-      case(1): t |=  ((d_data_reg >> 63) & 0x1) << 0; break;
-      case(2): t |= !((d_data_reg >> 63) & 0x1) << 0; break;
-      default: throw std::out_of_range ("Access code flag out of range");
-    }
+    t |= d_flip ^ (((d_data_reg >> 63) & 0x1) << 0);
     t |= ((d_flag_reg >> 63) & 0x1) << 1;      // flag bit
     out[i] = t;
     
     // compute hamming distance between desired access code and current data
     unsigned long long wrong_bits = 0;
-    unsigned int nwrong = d_threshold+1, nwrong_temp = 0;
-    int new_flag = 0, new_flag_temp = 0;
+    unsigned int nwrong = d_threshold+1;
+    int new_flag = 0;
 
-    for(unsigned int j = 0; j < 2; j++)
-    {
-      wrong_bits  = (d_data_reg ^ d_access_code[j]) & d_mask;
-      nwrong_temp = gr_count_bits64(wrong_bits);
-      new_flag_temp = nwrong_temp <= d_threshold;
-      if(nwrong_temp < nwrong)
-       nwrong = nwrong_temp;
-      if(new_flag_temp)
-       new_flag = j+1;    // mark which access code correlated closest
-    }
+    wrong_bits  = (d_data_reg ^ d_access_code) & d_mask;
+    nwrong = gr_count_bits64(wrong_bits);
 
-    //if(new_flag) 
-    //  printf("%llx  :  %llx ==> %llx\n", d_access_code[0], d_access_code[1], 
d_data_reg);
+    // test for access code with up to threshold errors or its compelement
+    new_flag = (nwrong <= d_threshold) || (nwrong >= (64-d_threshold));
+
+#if 0   
+    if(new_flag) {
+      printf("%llx  ==>  %llx  :  d_flip=%u\n", d_access_code, d_data_reg, 
d_flip);
+    }
+#endif
 
     // shift in new data and new flag
     d_data_reg = (d_data_reg << 1) | (in[i] & 0x1);
     d_flag_reg = (d_flag_reg << 1);
     if (new_flag) {
-      d_rotation = new_flag;
       d_flag_reg |= d_flag_bit;
-      //printf("\nAccess Code Found, bad bits = %d\n", nwrong);
+      d_flip = nwrong >= (64-d_threshold);   // flip bits if this is true
     }
   }
 

Index: gr_correlate_access_code_bb.h
===================================================================
RCS file: 
/sources/gnuradio/gnuradio-core/src/lib/general/gr_correlate_access_code_bb.h,v
retrieving revision 1.2
retrieving revision 1.3
diff -u -b -r1.2 -r1.3
--- gr_correlate_access_code_bb.h       28 Jun 2006 18:30:38 -0000      1.2
+++ gr_correlate_access_code_bb.h       29 Jun 2006 20:26:54 -0000      1.3
@@ -54,7 +54,7 @@
   friend gr_correlate_access_code_bb_sptr 
   gr_make_correlate_access_code_bb (const std::string &access_code, int 
threshold);
  private:
-  unsigned long long d_access_code[2]; // access code to locate start of packet
+  unsigned long long d_access_code;    // access code to locate start of packet
                                         //   access code is left justified in 
the word
   unsigned long long d_data_reg;       // used to look for access_code
   unsigned long long d_flag_reg;       // keep track of decisions
@@ -62,7 +62,7 @@
   unsigned long long d_mask;           // masks access_code bits (top N bits 
are set where
                                         //   N is the number of bits in the 
access code)
   unsigned int      d_threshold;       // how many bits may be wrong in sync 
vector
-  unsigned int       d_rotation;        // derotate the phase of the input
+  unsigned int       d_flip;            // flip bits if 180 degress out of sync
 
 
  protected: