CurieI2S - minor fixes/improvements

-prevent buffer overflow in I2S_RxCallback example
-calculate delay for any sample rate

Author: bigdinotech

libraries/CurieI2S/examples/I2S_RxCallback/I2S_RxCallback.ino

@@ -49,5 +49,6 @@ void rxDataReceived()
   while(CurieI2S.available())
   {
     dataBuff[count++] =  CurieI2S.requestdword();   
+    count %= 256; //prevent buffer overflow and just write data in front of the buffer.
   }
 }

libraries/CurieI2S/src/CurieI2S.cpp

@@ -222,7 +222,8 @@ static void i2sInterruptHandler(void)
                 //TXFIFO and tx buffer empty
 
                 //last frame delay
-                delayTicks(960);
+                //delayTicks(960);
+                CurieI2S.lastFrameDelay();
                 //stop transmission
                 *I2S_CTRL = *I2S_CTRL & 0xFDFFFFFE;
 
@@ -357,6 +358,9 @@ void Curie_I2S::setSampleRate(uint32_t dividerValue)
     i2s_srr &= I2S_SAMPLERATE_MASK;
     i2s_srr |= dividerValue;
     *I2S_SRR = i2s_srr;
+    
+    //set frameDelay value.
+    frameDelay = (dividerValue&0x000000FF)*32*2;
 }
 
 void Curie_I2S::setResolution(uint32_t resolution)
@@ -632,6 +636,11 @@ uint8_t Curie_I2S::getRxFIFOLength()
     return fifolength;
 }
 
+void Curie_I2S::lastFrameDelay()
+{
+    delayTicks(frameDelay);
+}
+
 void Curie_I2S::attachRxInterrupt(void (*userCallBack)())
 {
     i2s_rxCB = userCallBack;

libraries/CurieI2S/src/CurieI2S.h

@@ -96,6 +96,9 @@ class Curie_I2S
 {
     private:
         uint32_t clock;
+        
+        int frameDelay = 0;
+        
         bool useDMA;
 
         // initializes i2s interface
@@ -202,6 +205,8 @@ class Curie_I2S
 
         uint8_t getRxFIFOLength();
 
+        void lastFrameDelay();
+        
         // Attach user callback that is triggered when there is data pushed into the rx buffer from the RX_FIFO
         void attachRxInterrupt(void (*userCallBack)());