Added configurable phase inversion to M17 demodulator. Forced enabling of phase inversion for MD3x0 VHF radios.

openrtx/include/protocols/M17/M17Demodulator.h

@@ -109,6 +109,13 @@ public:
      */
     bool isLocked();
 
+    /**
+     * Invert baseband signal phase before decoding.
+     *
+     * @param status: if set to true signal phase is inverted.
+     */
+    void invertPhase(const bool status);
+
 private:
 
     /**
@@ -150,6 +157,7 @@ private:
     bool         newFrame;         ///< A new frame has been fully decoded.
     int16_t      basebandBridge[M17_BRIDGE_SIZE] = { 0 }; ///< Bridge buffer
     int16_t      phase;            ///< Phase of the signal w.r.t. sampling
+    bool         invPhase;         ///< Invert signal phase
 
     /*
      * State variables

openrtx/include/rtx/rtx.h

@@ -57,6 +57,7 @@ typedef struct
 
     char     source_address[10];      /**< M17 call source address  */
     char     destination_address[10]; /**< M17 call routing address */
+    bool     invertRxPhase;           /**< M17 RX phase inversion   */
 }
 rtxStatus_t;
 

openrtx/src/core/threads.c

@@ -103,12 +103,13 @@ void *ui_task(void *arg)
             rtx_cfg.rxTone = ctcss_tone[state.channel.fm.rxTone];
             rtx_cfg.txToneEn = state.channel.fm.txToneEn;
             rtx_cfg.txTone = ctcss_tone[state.channel.fm.txTone];
-            pthread_mutex_unlock(&rtx_mutex);
 
             // Copy new M17 source and destination addresses
             strncpy(rtx_cfg.source_address, state.settings.callsign, 10);
             strncpy(rtx_cfg.destination_address, state.m17_data.dst_addr, 10);
 
+            pthread_mutex_unlock(&rtx_mutex);
+
             rtx_configure(&rtx_cfg);
             sync_rtx = false;
         }

openrtx/src/protocols/M17/M17Demodulator.cpp

@@ -435,6 +435,7 @@ bool M17Demodulator::update()
         for(size_t i = 0; i < baseband.len; i++)
         {
             float elem = static_cast< float >(baseband.data[i]);
+            if(invPhase) elem = 0.0f - elem;
             baseband.data[i]  = static_cast< int16_t >(M17::rrc_24k(elem));
         }
 
@@ -574,3 +575,8 @@ bool M17Demodulator::update()
 
     return newFrame;
 }
+
+void M17Demodulator::invertPhase(const bool status)
+{
+    invPhase = status;
+}

openrtx/src/rtx/OpMode_M17.cpp

@@ -66,6 +66,12 @@ void OpMode_M17::update(rtxStatus_t *const status, const bool newCfg)
 {
     (void) newCfg;
 
+    // Force inversion of RX phase for MD3x0 VHF radios
+    #ifdef PLATFORM_MD3x0
+    const hwInfo_t* hwinfo = platform_getHwInfo();
+    status->invertRxPhase |= hwinfo->vhf_band;
+    #endif
+
     // Main FSM logic
     switch(status->opStatus)
     {
@@ -135,6 +141,7 @@ void OpMode_M17::rxState(rtxStatus_t *const status)
     {
         decoder.reset();
         demodulator.startBasebandSampling();
+        demodulator.invertPhase(status->invertRxPhase);
 
         audio_enableAmp();
         codec_startDecode(SINK_SPK);

openrtx/src/rtx/rtx.cpp

@@ -58,6 +58,7 @@ void rtx_init(pthread_mutex_t *m)
     rtxStatus.rxTone        = 0;
     rtxStatus.txToneEn      = 0;
     rtxStatus.txTone        = 0;
+    rtxStatus.invertRxPhase = false;
     currMode = &noMode;
 
     /*