Complete WAV generation

src/Makefile

@@ -5,7 +5,7 @@ app: rds.o waveforms.o pi_fm_rds.o
 	$(CC) -o pi_fm_rds rds.o waveforms.o pi_fm_rds.o -lm
 
 rds_wav: rds.o waveforms.o rds_wav.o
-	$(CC) -o rds_wav rds_wav.o rds.o waveforms.o
+	$(CC) -o rds_wav rds_wav.o rds.o waveforms.o -lsndfile
 
 rds.o: rds.c waveforms.h
 	$(CC) $(CFLAGS) rds.c

src/generate_waveforms.py

@@ -24,12 +24,6 @@ header = u"""
 outc.write(header)
 outh.write(header)
 
-def format_number(x):
-    if abs(x) < 1e-10:
-        return u"0"
-    else:
-        return unicode(x)
-
 def generate_bit_in_context(pattern, name):
     offset = 240
     l = 96
@@ -44,7 +38,9 @@ def generate_bit_in_context(pattern, name):
     
     outc.write(u"float waveform_{name}[] = {{{values}}};\n\n".format(
         name = name,
-        values = u", ".join(map(format_number, out))))
+        values = u", ".join(map(unicode, out/3.))))
+        # note: need to limit the amplitude so as not to saturate when the biphase
+        # waveforms are summed
     
     outh.write(u"extern float waveform_{name}[{size}];\n".format(name=name, size=len(out)))
 

src/rds_wav.c

@@ -1,24 +1,76 @@
+/*
+    PiFmRds - FM/RDS transmitter for the Raspberry Pi
+    Copyright (C) 2014 Christophe Jacquet, F8FTK
+    
+    See https://github.com/ChristopheJacquet/PiFmRds
+    
+    rds_wav.c is a test program that writes a RDS baseband signal to a WAV
+    file. It requires libsndfile.
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+
 #include <stdio.h>
+#include <stdlib.h>
+#include <sndfile.h>
 
 #include "rds.h"
 
-#define LENGTH 100000
+#define LENGTH 114000
 
 /* Simple test program */
 int main(int argc, char **argv) {
-    set_rds_params(0x1234, "Hello!  World of the RaspberryPi!");
+    if(argc < 3) {
+        fprintf(stderr, "Error: missing argument.\n");
+        fprintf(stderr, "Syntax: rds_wav <out.wav> <text>\n");
+        return EXIT_FAILURE;
+    }
+    
+    set_rds_params(0x1234, argv[2]);
     
     float buffer[LENGTH];
-    int count = 0;
     
-    for(int j=0; j<20; j++) {
+    // Set the format of the output file
+    SNDFILE *outf;
+    SF_INFO sfinfo;
+    sfinfo.frames = LENGTH;
+    sfinfo.samplerate = 228000;
+    sfinfo.channels = 1;
+    sfinfo.format = SF_FORMAT_WAV | SF_FORMAT_PCM_16;
+    sfinfo.sections = 1;
+    sfinfo.seekable = 0;
+    
+    // Open the output file
+    if (! (outf = sf_open(argv[1], SFM_WRITE, &sfinfo))) {
+        fprintf(stderr, "Error: could not open output file %s.\n", argv[1]) ;
+        return EXIT_FAILURE;
+    }
+
+
+    for(int j=0; j<40; j++) {
         get_rds_samples(buffer, LENGTH);
 
-        fprintf(stderr, "Iteration %d count=%d\n", j, count);
-
-        for(int i=0; i<LENGTH; i++) {
-            printf("%c", (((int)(buffer[i]*50))));
-            count++;
+        if(sf_write_float(outf, buffer, LENGTH) != LENGTH) {
+            fprintf(stderr, "Error: writing to file %s.\n", argv[1]);
+            return EXIT_FAILURE;
         }
     }
+    
+    if(sf_close(outf) ) {
+        fprintf(stderr, "Error: closing file %s.\n", argv[1]);
+    }
+    
+    return EXIT_SUCCESS;
 }