Merge pull request drowe67#309 from DJ2LS/ls-fmin-fmax

New function: freedv_set_fmin_fmax

Author: drowe67

src/freedv_api.c

@@ -1372,6 +1372,33 @@ int freedv_get_bits_per_modem_frame       (struct freedv *f) {return f->bits_per
 int freedv_get_rx_status                  (struct freedv *f) {return f->rx_status;}
 void freedv_get_fsk_S_and_N               (struct freedv *f, float *S, float *N) { *S = f->fsk_S[0]; *N = f->fsk_N[0]; }
 
+
+/*---------------------------------------------------------------------------*\
+
+  FUNCTIONS...: freedv_set_tuning_range
+  AUTHOR......: Simon Lang - DJ2LS
+  DATE CREATED: 18 feb 2022
+  DEFAULT.....: fmin: -50.0Hz fmax: 50.0Hz
+  DESCRIPTION.:
+  
+  |<---fmin - | rx centre frequency | + fmax--->|
+  
+  Useful for handling frequency offsets, 
+  e.g. caused by an imprecise VFO, the trade off is more CPU power is required.  
+  
+\*---------------------------------------------------------------------------*/
+int freedv_set_tuning_range(struct freedv *freedv, float val_fmin, float val_fmax) {
+
+    if (is_ofdm_data_mode(freedv) && (strcmp(freedv->ofdm->data_mode, "burst") == 0)) {
+        freedv->ofdm->fmin = val_fmin;
+        freedv->ofdm->fmax = val_fmax;
+        return 1;
+    } else {
+        return 0;
+    }
+}
+
+
 int freedv_get_n_max_speech_samples(struct freedv *f) {
     /* When "passing through" demod samples to the speech output
        (e.g. no sync and squelch off) f->nin bounces around with

src/freedv_api.h

@@ -240,6 +240,7 @@ void freedv_set_phase_est_bandwidth_mode(struct freedv *f, int val);
 void freedv_set_eq                      (struct freedv *f, int val);
 void freedv_set_frames_per_burst        (struct freedv *f, int framesperburst);
 void freedv_passthrough_gain            (struct freedv *f, float g);
+int freedv_set_tuning_range             (struct freedv *freedv, float val_fmin, float val_fmax);
 
 // Get parameters -------------------------------------------------------------------------
 

src/ofdm.c

@@ -219,6 +219,8 @@ struct OFDM *ofdm_create(const struct OFDM_CONFIG *config) {
         ofdm->clip_en = false;
         ofdm->foff_limiter = false;
         ofdm->data_mode = "";
+        ofdm->fmin = -50.0;                       /* frequency minimum for ofdm acquisition range */
+        ofdm->fmax = 50.0;                        /* frequency maximum for ofdm acquisition range */
         memset(ofdm->tx_uw, 0, ofdm->nuwbits);
     } else {
         /* Use the users values */
@@ -252,6 +254,8 @@ struct OFDM *ofdm_create(const struct OFDM_CONFIG *config) {
         ofdm->clip_en = config->clip_en;
         memcpy(ofdm->tx_uw, config->tx_uw, ofdm->nuwbits);
         ofdm->data_mode = config->data_mode;
+        ofdm->fmin = config->fmin;              /* frequency minimum for ofdm acquisition range */
+        ofdm->fmax = config->fmax;              /* frequency maximum for ofdm acquisition range */
 
     }
 
@@ -297,6 +301,9 @@ struct OFDM *ofdm_create(const struct OFDM_CONFIG *config) {
     ofdm->config.clip_en = ofdm->clip_en;
     memcpy(ofdm->config.tx_uw, ofdm->tx_uw, ofdm->nuwbits);
     ofdm->config.data_mode = ofdm->data_mode;
+    ofdm->config.fmin = ofdm->fmin;
+    ofdm->config.fmax = ofdm->fmax;
+    
 
     /* Calculate sizes from config param */
 
@@ -421,6 +428,10 @@ struct OFDM *ofdm_create(const struct OFDM_CONFIG *config) {
     ofdm->nin = ofdm->samplesperframe;
     ofdm->mean_amp = 0.0f;
     ofdm->foff_metric = 0.0f;
+    
+    ofdm->fmin = -50.0f;
+    ofdm->fmax = 50.0f;
+    
     /*
      * Unique Word symbol placement.  Note we need to group the UW
      * bits so they fit into symbols.  The LDPC decoder works on
@@ -1158,9 +1169,9 @@ static void burst_acquisition_detector(struct OFDM *ofdm,
 
     float fmin, fmax, fstep;
     int tstep;
-    
+
     // initial search over coarse grid
-    tstep = 4; fstep = 5; fmin = -50.0; fmax = 50.0;
+    tstep = 4; fstep = 5; fmin = ofdm->fmin; fmax = ofdm->fmax;
     *timing_mx = est_timing_and_freq(ofdm, ct_est, foff_est,
                                  &rx[n], 2*ofdm->samplesperframe, 
                                  known_sequence, ofdm->samplesperframe,

src/ofdm_internal.h

@@ -106,6 +106,8 @@ struct OFDM_CONFIG {
     bool  clip_en;
     char mode[16];        /* OFDM mode in string form */
     char *data_mode;
+    float fmin;
+    float fmax;
 };
 
 struct OFDM {
@@ -165,6 +167,9 @@ struct OFDM {
     float tx_nlower;      /* TX lowest carrier freq */
     float rx_nlower;      /* RX lowest carrier freq */
     float doc;            /* division of radian circle */
+    
+    float fmin;
+    float fmax;
 
     // Pointers