Allow non-standard frequencies and frequency deviations

README.md

@@ -56,6 +56,7 @@ All arguments are optional:
 * `-rt` specifies the radiotext (RT) to be transmitted. Limit: 64 characters. Example: `-rt 'Hello, world!'`.
 * `-ctl` specifies a named pipe (FIFO) to use as a control channel to change PS and RT at run-time (see below).
 * `-ppm` specifies your Raspberry Pi's oscillator error in parts per million (ppm), see below.
+* `-dev` specifies the frequency deviation (in KHz). Example `-dev 25.0`.
 
 By default the PS changes back and forth between `Pi-FmRds` and a sequence number, starting at `00000000`. The PS changes around one time per second.
 
@@ -166,6 +167,7 @@ The samples are played by `pi_fm_rds.c` that is adapted from Richard Hirst's [Pi
 
 ## History
 
+* 2014-11-08: support for non-standard frequencies and frequency deviations
 * 2014-11-01: support for toggling the Traffic Announcement (TA) flag at run-time
 * 2014-10-19: bugfix (cleanly stop the DMA engine when the specified file does not exist, or it's not possible to read from stdin)
 * 2014-08-04: bugfix (ppm now uses floats)

src/pi_fm_rds.c

@@ -156,7 +156,6 @@
 
 // The deviation specifies how wide the signal is. Use 25.0 for WBFM
 // (broadcast radio) and about 3.5 for NBFM (walkie-talkie style radio)
-#define DEVIATION        25.0
 
 
 typedef struct {
@@ -217,13 +216,23 @@ static void
 fatal(char *fmt, ...)
 {
     va_list ap;
-
+    fprintf(stderr,"ERROR: ");
     va_start(ap, fmt);
     vfprintf(stderr, fmt, ap);
     va_end(ap);
     terminate(0);
 }
 
+static void
+warn(char *fmt, ...)
+{
+    va_list ap;
+    fprintf(stderr,"WARNING: ");
+    va_start(ap, fmt);
+    vfprintf(stderr, fmt, ap);
+    va_end(ap);
+}
+
 static uint32_t
 mem_virt_to_phys(void *virt)
 {
@@ -271,7 +280,7 @@ map_peripheral(uint32_t base, uint32_t len)
 #define DATA_SIZE 5000
 
 
-int tx(uint32_t carrier_freq, char *audio_file, uint16_t pi, char *ps, char *rt, float ppm, char *control_pipe) {
+int tx(uint32_t carrier_freq, char *audio_file, uint16_t pi, char *ps, char *rt, float ppm, char *control_pipe, float deviation) {
     int i, fd, pid;
     char pagemap_fn[64];
 
@@ -492,7 +501,7 @@ int tx(uint32_t carrier_freq, char *audio_file, uint16_t pi, char *ps, char *rt,
                 data_index = 0;
             }
 
-            float dval = data[data_index] * (DEVIATION / 10.);
+            float dval = data[data_index] * (deviation / 10.);
             data_index++;
             data_len--;
 
@@ -521,6 +530,7 @@ int main(int argc, char **argv) {
     char *rt = "PiFmRds: live FM-RDS transmission from the RaspberryPi";
     uint16_t pi = 0x1234;
     float ppm = 0;
+    float deviation = 25.0;
 
 
     // Parse command-line arguments
@@ -537,7 +547,7 @@ int main(int argc, char **argv) {
             i++;
             carrier_freq = 1e6 * atof(param);
             if(carrier_freq < 87500000 || carrier_freq > 108000000)
-                fatal("Incorrect frequency specification. Must be in megahertz, of the form 107.9\n");
+                warn("Frequency should be in megahertz between 87.5 and 108.0, but is %f MHz\n",atof(param));
         } else if(strcmp("-pi", arg)==0 && param != NULL) {
             i++;
             pi = (uint16_t) strtol(param, NULL, 16);
@@ -553,14 +563,17 @@ int main(int argc, char **argv) {
         } else if(strcmp("-ctl", arg)==0 && param != NULL) {
             i++;
             control_pipe = param;
+        } else if(strcmp("-dev", arg)==0 && param != NULL) {
+            i++;
+            deviation = atof(param);
         } else {
             fatal("Unrecognised argument: %s\n"
             "Syntax: pi_fm_rds [-freq freq] [-audio file] [-ppm ppm_error] [-pi pi_code]\n"
-            "                  [-ps ps_text] [-rt rt_text] [-ctl control_pipe]\n", arg);
+            "                  [-ps ps_text] [-rt rt_text] [-ctl control_pipe] [-dev deviation]\n", arg);
         }
     }
 
-    int errcode = tx(carrier_freq, audio_file, pi, ps, rt, ppm, control_pipe);
+    int errcode = tx(carrier_freq, audio_file, pi, ps, rt, ppm, control_pipe, deviation);
 
     terminate(errcode);
 }