Small refactoring of M17 modulator.

- made start() function return a boolean indicating the actual modulator status
- moved sending of preamble to a dedicated function
- renamed send() function to sendFrame()

openrtx/include/protocols/M17/M17Modulator.hpp

@@ -64,9 +64,16 @@ public:
     void terminate();
 
     /**
-     * Start baseband transmission and send an 80ms preamble.
+     * Start the modulator.
+     *
+     * @return true if the modulator has been successfully started.
      */
-    void start();
+    bool start();
+
+    /**
+     * Send an 80ms long transmission preamble.
+     */
+    void sendPreamble();
 
     /**
      * Generate and transmit the baseband signal obtained by 4FSK modulation of
@@ -76,7 +83,7 @@ public:
      * @param isLast: flag signalling that current block is the last one being
      * transmitted.
      */
-    void send(const frame_t& frame);
+    void sendFrame(const frame_t& frame);
 
     /**
      * Terminate baseband transmission.

openrtx/src/protocols/M17/M17Modulator.cpp

@@ -74,12 +74,33 @@ void M17Modulator::terminate()
     baseband_buffer.reset();
 }
 
-void M17Modulator::start()
+bool M17Modulator::start()
 {
-    if(txRunning) return;
+    if(txRunning)
+        return true;
+
+    #ifndef PLATFORM_LINUX
+    outPath = audioPath_request(SOURCE_MCU, SINK_RTX, PRIO_TX);
+    if(outPath < 0)
+        return false;
+
+    outStream = audioStream_start(outPath, baseband_buffer.get(),
+                                  2*M17_FRAME_SAMPLES, M17_TX_SAMPLE_RATE,
+                                  STREAM_OUTPUT | BUF_CIRC_DOUBLE);
+
+    if(outStream < 0)
+        return false;
+
+    idleBuffer = outputStream_getIdleBuffer(outStream);
+    #endif
 
     txRunning = true;
 
+    return true;
+}
+
+void M17Modulator::sendPreamble()
+{
     // Fill symbol buffer with preamble, made of alternated +3 and -3 symbols
     for(size_t i = 0; i < symbols.size(); i += 2)
     {
@@ -89,21 +110,7 @@ void M17Modulator::start()
 
     // Generate baseband signal and then start transmission
     symbolsToBaseband();
-    #ifndef PLATFORM_LINUX
-    outPath = audioPath_request(SOURCE_MCU, SINK_RTX, PRIO_TX);
-    if(outPath < 0)
-    {
-        txRunning = false;
-        return;
-    }
-
-    outStream = audioStream_start(outPath, baseband_buffer.get(),
-                                  2*M17_FRAME_SAMPLES, M17_TX_SAMPLE_RATE,
-                                  STREAM_OUTPUT | BUF_CIRC_DOUBLE);
-    idleBuffer = outputStream_getIdleBuffer(outStream);
-    #else
     sendBaseband();
-    #endif
 
     // Repeat baseband generation and transmission, this makes the preamble to
     // be long 80ms (two frames)
@@ -111,8 +118,7 @@ void M17Modulator::start()
     sendBaseband();
 }
 
-
-void M17Modulator::send(const frame_t& frame)
+void M17Modulator::sendFrame(const frame_t& frame)
 {
     auto it = symbols.begin();
     for(size_t i = 0; i < frame.size(); i++)

openrtx/src/rtx/OpMode_M17.cpp

@@ -326,7 +326,8 @@ void OpMode_M17::txState(rtxStatus_t *const status)
 
         modulator.invertPhase(invertTxPhase);
         modulator.start();
-        modulator.send(m17Frame);
+        modulator.sendPreamble();
+        modulator.sendFrame(m17Frame);
     }
 
     payload_t dataFrame;
@@ -344,12 +345,12 @@ void OpMode_M17::txState(rtxStatus_t *const status)
     }
 
     encoder.encodeStreamFrame(dataFrame, m17Frame, lastFrame);
-    modulator.send(m17Frame);
+    modulator.sendFrame(m17Frame);
 
     if(lastFrame)
     {
         encoder.encodeEotFrame(m17Frame);
-        modulator.send(m17Frame);
+        modulator.sendFrame(m17Frame);
         modulator.stop();
     }
 }