Corrected RRC gain and changed HR_C5000 modulation factor and input gain to have the correct 2.4kHz deviation when transmitting M17 with an MD3x0 radio

openrtx/include/protocols/M17/M17Modulator.h

@@ -116,7 +116,7 @@ private:
     static constexpr float  M17_RRC_GAIN          = 15000.0f;
     static constexpr float  M17_RRC_OFFSET        = 11500.0f;
     #else
-    static constexpr float  M17_RRC_GAIN          = 7168.0f;
+    static constexpr float  M17_RRC_GAIN          = 23000.0f;
     static constexpr float  M17_RRC_OFFSET        = 0.0f;
     #endif
 

openrtx/src/protocols/M17/M17Modulator.cpp

@@ -100,8 +100,8 @@ void M17Modulator::generateBaseband()
     for(size_t i = 0; i < M17_FRAME_SAMPLES_48K; i++)
     {
         float elem    = static_cast< float >(idleBuffer[i]);
-        idleBuffer[i] = static_cast< int16_t >((M17::rrc_48k(elem) * M17_RRC_GAIN)
-                                                - M17_RRC_OFFSET);
+        elem          = M17::rrc_48k(elem * M17_RRC_GAIN) - M17_RRC_OFFSET;
+        idleBuffer[i] = static_cast< int16_t >(elem);
     }
 }
 

platform/drivers/baseband/HR_Cx000.h

@@ -142,7 +142,7 @@ public:
     inline void setModFactor(const uint8_t mf)
     {
         writeReg(M::CONFIG, 0x35, mf);      // FM modulation factor
-        writeReg(M::CONFIG, 0x3F, 0x04);    // FM Limiting modulation factor (HR_C6000)
+        writeReg(M::CONFIG, 0x3F, 0x07);    // FM Limiting modulation factor (HR_C6000)
     }
 
     /**

platform/drivers/baseband/radio_MD3x0.cpp

@@ -214,7 +214,7 @@ void radio_setOpmode(const enum opmode mode)
             gpio_clearPin(DMR_SW);      // Disconnect analog paths for DMR
             gpio_setPin(FM_SW);         // Enable analog RX stage after superhet
             C5000.fmMode();             // HR_C5000 in FM mode
-            C5000.setInputGain(-5);     // Input gain in dB, found experimentally
+            C5000.setInputGain(-3);     // Input gain in dB, found experimentally
             break;
 
         default: