Diff: cmsis_dsp/SupportFunctions/arm_q15_to_q7.c

Revision:

1:fdd22bb7aa52

Child:

2:da51fb522205

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/cmsis_dsp/SupportFunctions/arm_q15_to_q7.c	Wed Nov 28 12:30:09 2012 +0000
@@ -0,0 +1,146 @@
+/* ----------------------------------------------------------------------------    
+* Copyright (C) 2010 ARM Limited. All rights reserved.    
+*    
+* $Date:        15. February 2012  
+* $Revision:     V1.1.0  
+*    
+* Project:         CMSIS DSP Library    
+* Title:        arm_q15_to_q7.c    
+*    
+* Description:    Converts the elements of the Q15 vector to Q7 vector.  
+*    
+* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
+*  
+* Version 1.1.0 2012/02/15 
+*    Updated with more optimizations, bug fixes and minor API changes.  
+*   
+* Version 1.0.10 2011/7/15  
+*    Big Endian support added and Merged M0 and M3/M4 Source code.   
+*    
+* Version 1.0.3 2010/11/29   
+*    Re-organized the CMSIS folders and updated documentation.    
+*     
+* Version 1.0.2 2010/11/11    
+*    Documentation updated.     
+*    
+* Version 1.0.1 2010/10/05     
+*    Production release and review comments incorporated.    
+*    
+* Version 1.0.0 2010/09/20     
+*    Production release and review comments incorporated.    
+* ---------------------------------------------------------------------------- */
+
+#include "arm_math.h"
+
+/**    
+ * @ingroup groupSupport    
+ */
+
+/**    
+ * @addtogroup q15_to_x    
+ * @{    
+ */
+
+
+/**    
+ * @brief Converts the elements of the Q15 vector to Q7 vector.     
+ * @param[in]       *pSrc points to the Q15 input vector    
+ * @param[out]      *pDst points to the Q7 output vector   
+ * @param[in]       blockSize length of the input vector    
+ * @return none.    
+ *    
+ * \par Description:    
+ *    
+ * The equation used for the conversion process is:    
+ *   
+ * <pre>    
+ *     pDst[n] = (q7_t) pSrc[n] >> 8;   0 <= n < blockSize.    
+ * </pre>   
+ *   
+ */
+
+
+void arm_q15_to_q7(
+  q15_t * pSrc,
+  q7_t * pDst,
+  uint32_t blockSize)
+{
+  q15_t *pIn = pSrc;                             /* Src pointer */
+  uint32_t blkCnt;                               /* loop counter */
+
+#ifndef ARM_MATH_CM0
+
+  /* Run the below code for Cortex-M4 and Cortex-M3 */
+  q31_t in1, in2;
+  q31_t out1, out2;
+
+  /*loop Unrolling */
+  blkCnt = blockSize >> 2u;
+
+  /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.    
+   ** a second loop below computes the remaining 1 to 3 samples. */
+  while(blkCnt > 0u)
+  {
+    /* C = (q7_t) A >> 8 */
+    /* convert from q15 to q7 and then store the results in the destination buffer */
+    in1 = *__SIMD32(pIn)++;
+    in2 = *__SIMD32(pIn)++;
+
+#ifndef ARM_MATH_BIG_ENDIAN
+
+    out1 = __PKHTB(in2, in1, 16);
+    out2 = __PKHBT(in2, in1, 16);
+
+#else
+
+    out1 = __PKHTB(in1, in2, 16);
+    out2 = __PKHBT(in1, in2, 16);
+
+#endif //      #ifndef ARM_MATH_BIG_ENDIAN
+
+    /* rotate packed value by 24 */
+    out2 = ((uint32_t) out2 << 8) | ((uint32_t) out2 >> 24);
+
+    /* anding with 0xff00ff00 to get two 8 bit values */
+    out1 = out1 & 0xFF00FF00;
+    /* anding with 0x00ff00ff to get two 8 bit values */
+    out2 = out2 & 0x00FF00FF;
+
+    /* oring two values(contains two 8 bit values) to get four packed 8 bit values */
+    out1 = out1 | out2;
+
+    /* store 4 samples at a time to destiantion buffer */
+    *__SIMD32(pDst)++ = out1;
+
+    /* Decrement the loop counter */
+    blkCnt--;
+  }
+
+  /* If the blockSize is not a multiple of 4, compute any remaining output samples here.    
+   ** No loop unrolling is used. */
+  blkCnt = blockSize % 0x4u;
+
+#else
+
+  /* Run the below code for Cortex-M0 */
+
+  /* Loop over blockSize number of values */
+  blkCnt = blockSize;
+
+#endif /* #ifndef ARM_MATH_CM0 */
+
+  while(blkCnt > 0u)
+  {
+    /* C = (q7_t) A >> 8 */
+    /* convert from q15 to q7 and then store the results in the destination buffer */
+    *pDst++ = (q7_t) (*pIn++ >> 8);
+
+    /* Decrement the loop counter */
+    blkCnt--;
+  }
+
+}
+
+/**    
+ * @} end of q15_to_x group    
+ */