From bfc6f5dea0b16ddf5865623174f305389cc0f577 Mon Sep 17 00:00:00 2001
From: ha7ilm <retzlerandras@gmail.com>
Date: Sun, 30 Apr 2017 22:23:21 +0200
Subject: [PATCH] Working RRC filter design

---
 csdr.c    | 21 +++++++++++++--------
 libcsdr.c |  8 ++++----
 2 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/csdr.c b/csdr.c
index 0c415ee..5cc9f15 100755
--- a/csdr.c
+++ b/csdr.c
@@ -3039,22 +3039,26 @@ int main(int argc, char *argv[])
     {
         if(argc<=2) return badsyntax("required parameter <matched_filter_type> is missing.");
         matched_filter_type_t type = matched_filter_get_type_from_string(argv[2]);
-        int samples_per_symbol = 0;
 
+        int samples_per_symbol = 0;
         if(argc<=3) return badsyntax("required parameter <samples_per_symbol> is missing.");
         sscanf(argv[3],"%d",&samples_per_symbol);
 
         int num_taps = 0;
-        if(argc<=4 && type!=MATCHED_FILTER_COSINE) 
-            return badsyntax("required parameter <num_taps> is missing.");
-        sscanf(argv[4],"%d",&num_taps);
+        if(type!=MATCHED_FILTER_COSINE)
+        {
+            if(argc<=4) return badsyntax("required parameter <num_taps> is missing.");
+            sscanf(argv[4],"%d",&num_taps);
+        }
+        else num_taps = (2*samples_per_symbol)+1;
 
         float beta = 0;
-        if(argc<=5 && type==MATCHED_FILTER_RRC) 
-            return badsyntax("required parameter <beta> is missing.");
-        sscanf(argv[5],"%f",&beta);
+        if(type==MATCHED_FILTER_RRC)
+        {
+            if(argc<=5) return badsyntax("required parameter <beta> is missing.");
+            sscanf(argv[5],"%f",&beta);
+        }
 
-        if(type==MATCHED_FILTER_COSINE) num_taps = (2*samples_per_symbol)+1;
         float* taps = (float*)malloc(sizeof(float)*num_taps);
         switch(type)
         {
@@ -3065,6 +3069,7 @@ int main(int argc, char *argv[])
             firdes_cosine_f(taps, num_taps, samples_per_symbol);
             break;
         }
+        //fprintf(stderr, "beta = %f, num_taps = %d, samples_per_symbol = %d\n", beta, num_taps, samples_per_symbol);
 
         if(!sendbufsize(initialize_buffers())) return -2;
 
diff --git a/libcsdr.c b/libcsdr.c
index 89e4b10..ced77c1 100755
--- a/libcsdr.c
+++ b/libcsdr.c
@@ -2371,13 +2371,13 @@ int firdes_rrc_f(float* taps, int taps_length, int samples_per_symbol, float bet
 {
     //needs an odd taps_length
     int middle_i=taps_length/2;
-    taps[middle_i]=(1/samples_per_symbol)*(1+beta*(4/PI-1));
-    for(int i=1;i<taps_length/2;i++) 
+    taps[middle_i]=(1/(float)samples_per_symbol)*(1+beta*(4/PI-1));
+    for(int i=1;i<1+taps_length/2;i++) 
     {
         if(i==samples_per_symbol/(4*beta)) 
-            taps[middle_i+i]=taps[middle_i-i]=(beta/(samples_per_symbol*sqrt(2)))*((1+(2/PI))*sin(PI/(4*beta))+(1-(2/PI)*cos(PI/(4*beta))));
+            taps[middle_i+i]=taps[middle_i-i]=(beta/(samples_per_symbol*sqrt(2)))*((1+(2/PI))*sin(PI/(4*beta))+(1-(2/PI))*cos(PI/(4*beta)));
         else
-            taps[middle_i+i]=taps[middle_i-i]=(1/samples_per_symbol)*
+            taps[middle_i+i]=taps[middle_i-i]=(1/(float)samples_per_symbol)*
                 (sin(PI*(i/(float)samples_per_symbol)*(1-beta)) + 4*beta*(i/(float)samples_per_symbol)*cos(PI*(i/(float)samples_per_symbol)*(1+beta)))/
                 (PI*(i/(float)samples_per_symbol)*(1-powf(4*beta*(i/(float)samples_per_symbol),2)));
     }