Fixed behaviour when analog is disabled. Now the SPI bus is (mostly) …

…left alone and the audio still runs. Closes #7. We could use an improvement to the PRU code that removes any SPI transaction.

core/PRU.cpp

@@ -309,7 +309,12 @@ int PRU::initialise(int pru_num, int frames_per_buffer, int spi_channels, int mu
     /* Set up flags */
     pru_buffer_comm[PRU_SHOULD_STOP] = 0;
     pru_buffer_comm[PRU_CURRENT_BUFFER] = 0;
-    pru_buffer_comm[PRU_BUFFER_FRAMES] = context->analogFrames;
+    unsigned int pruFrames;
+    if(analog_enabled)
+        pruFrames = context->analogFrames;
+    else
+        pruFrames = context->audioFrames / 2; // PRU assumes 8 "fake" channels when SPI is disabled
+    pru_buffer_comm[PRU_BUFFER_FRAMES] = pruFrames;
     pru_buffer_comm[PRU_SHOULD_SYNC] = 0;
     pru_buffer_comm[PRU_SYNC_ADDRESS] = 0;
     pru_buffer_comm[PRU_SYNC_PIN_MASK] = 0;
@@ -531,23 +536,18 @@ int PRU::start(char * const filename)
     return 0;
 }
 
-#ifdef PRU_SIGXCPU_BUG_WORKAROUND
-extern bool gProcessAnalog;
-#endif /* PRU_SIGXCPU_BUG_WORKAROUND */
-
 // Main loop to read and write data from/to PRU
 void PRU::loop(RT_INTR *pru_interrupt, void *userData)
 {
 #ifdef BELA_USE_XENOMAI_INTERRUPTS
 	RTIME irqTimeout = PRU_SAMPLE_INTERVAL_NS * 1024;	// Timeout for PRU interrupt: about 10ms, much longer than any expected period
 #else
-	// Polling interval is 1/4 of the period
 	if(context->analogInChannels != context->analogOutChannels){
 		printf("Error: TODO: a different number of channels for inputs and outputs is not yet supported\n");
 		return;
 	}
-	unsigned int analogChannels = context->analogInChannels;
-	RTIME sleepTime = PRU_SAMPLE_INTERVAL_NS * (analogChannels / 2) * context->analogFrames / 4;
+	// Polling interval is 1/4 of the period
+	RTIME sleepTime = PRU_SAMPLE_INTERVAL_NS * (context->audioInChannels) * context->audioFrames / 4;
 #endif
 
 	uint32_t pru_audio_offset, pru_spi_offset;
@@ -582,13 +582,6 @@ void PRU::loop(RT_INTR *pru_interrupt, void *userData)
 	uint32_t lastPRUBuffer = 0;
 #endif
 
-#ifdef PRU_SIGXCPU_BUG_WORKAROUND
-	if(gProcessAnalog == false){
-		context->analogFrames = 0;
-		context->analogInChannels = 0;
-		context->analogOutChannels = 0;
-	}
-#endif
 
 	while(!gShouldStop) {
 #ifdef BELA_USE_XENOMAI_INTERRUPTS

core/RTAudio.cpp

@@ -78,9 +78,6 @@ int gRTAudioVerbose = 0;   						// Verbosity level for debugging
 int gAmplifierMutePin = -1;
 int gAmplifierShouldBeginMuted = 0;
 
-#ifdef PRU_SIGXCPU_BUG_WORKAROUND
-bool gProcessAnalog;
-#endif /* PRU_SIGXCPU_BUG_WORKAROUND */
 
 // Context which holds all the audio/sensor data passed to the render routines
 InternalBelaContext gContext;
@@ -193,14 +190,6 @@ int Bela_initAudio(BelaInitSettings *settings, void *userData)
 	gContext.audioInChannels = 2;
 	gContext.audioOutChannels = 2;
 
-#ifdef PRU_SIGXCPU_BUG_WORKAROUND
-	// TODO: see PRU bug mentioned above. We catch here if useAnalog was set to false, store it in gProcessAnalog
-	// and use this value to decide whether we should process the analogs in PRU::loop, but then we
-	// set it to true so that the PRU is init'd and the code runs AS IF the analogs were in use.
-	gProcessAnalog = settings->useAnalog;
-	settings->useAnalog = true;
-#endif /* PRU_SIGXCPU_BUG_WORKAROUND */
-
 	if(settings->useAnalog) {
 		gContext.audioFrames = settings->periodSize;
 

include/Bela.h

@@ -736,15 +736,4 @@ int Bela_startAuxiliaryTask(AuxiliaryTask task);
 /** @} */
 #include <Utilities.h>
 
-/**\cond HIDDEN_SYMBOLS
-// TODO: There is a bug in the PRU code that prevents it from working when SPI is disabled.
-// To work around it, we leave the SPI enabled ( as it does not affect the load of the ARM core), but
-// we avoid processing the analog channels, to save CPU time. We use global variable gProcessAnalog
-// in RTAudio.cpp and PRU.cpp to store the actual value of analog_enabled. To reproduce the bug,
-// undefine the line below and run with -N0 (analog disabled)
- */
-#define PRU_SIGXCPU_BUG_WORKAROUND
-/**
- * \endcond
- */
 #endif /* BELA_H_ */