correct 16-bit samples not signed extended on read/peek

Author: sandeepmistry

libraries/I2S/src/I2S.cpp

@@ -194,6 +194,11 @@ int I2SClass::read()
 
   read(&sample, _bitsPerSample / 8);
 
+  if (_bitsPerSample == 16 && (sample & 0x8000)) {
+    // sign extend value
+    sample |= 0xffff0000;
+  }
+
   return sample;
 }
 
@@ -212,6 +217,11 @@ int I2SClass::peek()
     __enable_irq();
   }
 
+  if (_bitsPerSample == 16 && (sample & 0x8000)) {
+    // sign extend value
+    sample |= 0xffff0000;
+  }
+
   return sample;
 }