Diff: src/Cortex-M4-M3/FilteringFunctions/arm_lms_norm_f32.c

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0:1014af42efd9

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+/* ----------------------------------------------------------------------  
+* Copyright (C) 2010 ARM Limited. All rights reserved.  
+*  
+* $Date:        29. November 2010  
+* $Revision: 	V1.0.3  
+*  
+* Project: 	    CMSIS DSP Library  
+* Title:	    arm_lms_norm_f32.c  
+*  
+* Description:	Processing function for the floating-point Normalised LMS.  
+*  
+* Target Processor: Cortex-M4/Cortex-M3
+*  
+* 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  
+*  
+* Version 0.0.7  2010/06/10   
+*    Misra-C changes done  
+* -------------------------------------------------------------------- */ 
+ 
+#include "arm_math.h" 
+ 
+/**  
+ * @ingroup groupFilters  
+ */ 
+ 
+/**  
+ * @defgroup LMS_NORM Normalized LMS Filters  
+ *  
+ * This set of functions implements a commonly used adaptive filter.  
+ * It is related to the Least Mean Square (LMS) adaptive filter and includes an additional normalization  
+ * factor which increases the adaptation rate of the filter.  
+ * The CMSIS DSP Library contains normalized LMS filter functions that operate on Q15, Q31, and floating-point data types.  
+ *  
+ * A normalized least mean square (NLMS) filter consists of two components as shown below.  
+ * The first component is a standard transversal or FIR filter.  
+ * The second component is a coefficient update mechanism.  
+ * The NLMS filter has two input signals.  
+ * The "input" feeds the FIR filter while the "reference input" corresponds to the desired output of the FIR filter.  
+ * That is, the FIR filter coefficients are updated so that the output of the FIR filter matches the reference input.  
+ * The filter coefficient update mechanism is based on the difference between the FIR filter output and the reference input.  
+ * This "error signal" tends towards zero as the filter adapts.  
+ * The NLMS processing functions accept the input and reference input signals and generate the filter output and error signal.  
+ * \image html LMS.gif "Internal structure of the NLMS adaptive filter"  
+ *  
+ * The functions operate on blocks of data and each call to the function processes  
+ * <code>blockSize</code> samples through the filter.  
+ * <code>pSrc</code> points to input signal, <code>pRef</code> points to reference signal,  
+ * <code>pOut</code> points to output signal and <code>pErr</code> points to error signal.  
+ * All arrays contain <code>blockSize</code> values.  
+ *  
+ * The API functions operate on a block-by-block basis.  
+ * Internally, the filter coefficients <code>b[n]</code> are updated on a sample-by-sample basis.  
+ * The convergence of the LMS filter is slower compared to the normalized LMS algorithm.  
+ *  
+ * \par Algorithm:  
+ * The output signal <code>y[n]</code> is computed by a standard FIR filter:  
+ * <pre>  
+ *     y[n] = b[0] * x[n] + b[1] * x[n-1] + b[2] * x[n-2] + ...+ b[numTaps-1] * x[n-numTaps+1]  
+ * </pre>  
+ *  
+ * \par  
+ * The error signal equals the difference between the reference signal <code>d[n]</code> and the filter output:  
+ * <pre>  
+ *     e[n] = d[n] - y[n].  
+ * </pre>  
+ *  
+ * \par  
+ * After each sample of the error signal is computed the instanteous energy of the filter state variables is calculated:  
+ * <pre>  
+ *    E = x[n]^2 + x[n-1]^2 + ... + x[n-numTaps+1]^2.  
+ * </pre>  
+ * The filter coefficients <code>b[k]</code> are then updated on a sample-by-sample basis:  
+ * <pre>  
+ *     b[k] = b[k] + e[n] * (mu/E) * x[n-k],  for k=0, 1, ..., numTaps-1  
+ * </pre>  
+ * where <code>mu</code> is the step size and controls the rate of coefficient convergence.  
+ *\par  
+ * In the APIs, <code>pCoeffs</code> points to a coefficient array of size <code>numTaps</code>.  
+ * Coefficients are stored in time reversed order.  
+ * \par  
+ * <pre>  
+ *    {b[numTaps-1], b[numTaps-2], b[N-2], ..., b[1], b[0]}  
+ * </pre>  
+ * \par  
+ * <code>pState</code> points to a state array of size <code>numTaps + blockSize - 1</code>.  
+ * Samples in the state buffer are stored in the order:  
+ * \par  
+ * <pre>  
+ *    {x[n-numTaps+1], x[n-numTaps], x[n-numTaps-1], x[n-numTaps-2]....x[0], x[1], ..., x[blockSize-1]}  
+ * </pre>  
+ * \par  
+ * Note that the length of the state buffer exceeds the length of the coefficient array by <code>blockSize-1</code> samples.  
+ * The increased state buffer length allows circular addressing, which is traditionally used in FIR filters,  
+ * to be avoided and yields a significant speed improvement.  
+ * The state variables are updated after each block of data is processed.  
+ * \par Instance Structure  
+ * The coefficients and state variables for a filter are stored together in an instance data structure.  
+ * A separate instance structure must be defined for each filter and  
+ * coefficient and state arrays cannot be shared among instances.  
+ * There are separate instance structure declarations for each of the 3 supported data types.  
+ *  
+ * \par Initialization Functions  
+ * There is also an associated initialization function for each data type.  
+ * The initialization function performs the following operations:  
+ * - Sets the values of the internal structure fields.  
+ * - Zeros out the values in the state buffer.  
+ * \par  
+ * Instance structure cannot be placed into a const data section and it is recommended to use the initialization function.  
+ * \par Fixed-Point Behavior:  
+ * Care must be taken when using the Q15 and Q31 versions of the normalised LMS filter.  
+ * The following issues must be considered:  
+ * - Scaling of coefficients  
+ * - Overflow and saturation  
+ *  
+ * \par Scaling of Coefficients:  
+ * Filter coefficients are represented as fractional values and  
+ * coefficients are restricted to lie in the range <code>[-1 +1)</code>.  
+ * The fixed-point functions have an additional scaling parameter <code>postShift</code>.  
+ * At the output of the filter's accumulator is a shift register which shifts the result by <code>postShift</code> bits.  
+ * This essentially scales the filter coefficients by <code>2^postShift</code> and  
+ * allows the filter coefficients to exceed the range <code>[+1 -1)</code>.  
+ * The value of <code>postShift</code> is set by the user based on the expected gain through the system being modeled.  
+ *  
+ * \par Overflow and Saturation:  
+ * Overflow and saturation behavior of the fixed-point Q15 and Q31 versions are  
+ * described separately as part of the function specific documentation below.  
+ */ 
+ 
+ 
+/**  
+ * @addtogroup LMS_NORM  
+ * @{  
+ */ 
+ 
+ 
+  /**  
+   * @brief Processing function for floating-point normalized LMS filter.  
+   * @param[in] *S points to an instance of the floating-point normalized LMS filter structure.  
+   * @param[in] *pSrc points to the block of input data.  
+   * @param[in] *pRef points to the block of reference data.  
+   * @param[out] *pOut points to the block of output data.  
+   * @param[out] *pErr points to the block of error data.  
+   * @param[in] blockSize number of samples to process.  
+   * @return none.  
+   */ 
+ 
+void arm_lms_norm_f32( 
+  arm_lms_norm_instance_f32 * S, 
+  float32_t * pSrc, 
+  float32_t * pRef, 
+  float32_t * pOut, 
+  float32_t * pErr, 
+  uint32_t blockSize) 
+{ 
+  float32_t *pState = S->pState;                 /* State pointer */ 
+  float32_t *pCoeffs = S->pCoeffs;               /* Coefficient pointer */ 
+  float32_t *pStateCurnt;                        /* Points to the current sample of the state */ 
+  float32_t *px, *pb;                            /* Temporary pointers for state and coefficient buffers */ 
+  float32_t mu = S->mu;                          /* Adaptive factor */ 
+  uint32_t numTaps = S->numTaps;                 /* Number of filter coefficients in the filter */ 
+  uint32_t tapCnt, blkCnt;                       /* Loop counters */ 
+  float32_t energy;                              /* Energy of the input */ 
+  float32_t sum, e, d;                           /* accumulator, error, reference data sample */ 
+  float32_t w, x0, in;                           /* weight factor, temporary variable to hold input sample and state */ 
+ 
+  /* Initializations of error,  difference, Coefficient update */ 
+  e = 0.0f; 
+  d = 0.0f; 
+  w = 0.0f; 
+ 
+  energy = S->energy; 
+  x0 = S->x0; 
+ 
+  /* S->pState points to buffer which contains previous frame (numTaps - 1) samples */ 
+  /* pStateCurnt points to the location where the new input data should be written */ 
+  pStateCurnt = &(S->pState[(numTaps - 1u)]); 
+ 
+  blkCnt = blockSize; 
+ 
+  while(blkCnt > 0u) 
+  { 
+    /* Copy the new input sample into the state buffer */ 
+    *pStateCurnt++ = *pSrc; 
+ 
+    /* Initialize pState pointer */ 
+    px = pState; 
+ 
+    /* Initialize coeff pointer */ 
+    pb = (pCoeffs); 
+ 
+    /* Read the sample from input buffer */ 
+    in = *pSrc++; 
+ 
+    /* Update the energy calculation */ 
+    energy -= x0 * x0; 
+    energy += in * in; 
+ 
+    /* Set the accumulator to zero */ 
+    sum = 0.0f; 
+ 
+    /* Loop unrolling.  Process 4 taps at a time. */ 
+    tapCnt = numTaps >> 2; 
+ 
+    while(tapCnt > 0u) 
+    { 
+      /* Perform the multiply-accumulate */ 
+      sum += (*px++) * (*pb++); 
+      sum += (*px++) * (*pb++); 
+      sum += (*px++) * (*pb++); 
+      sum += (*px++) * (*pb++); 
+ 
+      /* Decrement the loop counter */ 
+      tapCnt--; 
+    } 
+ 
+    /* If the filter length is not a multiple of 4, compute the remaining filter taps */ 
+    tapCnt = numTaps % 0x4u; 
+ 
+    while(tapCnt > 0u) 
+    { 
+      /* Perform the multiply-accumulate */ 
+      sum += (*px++) * (*pb++); 
+ 
+      /* Decrement the loop counter */ 
+      tapCnt--; 
+    } 
+ 
+    /* The result in the accumulator, store in the destination buffer. */ 
+    *pOut++ = sum; 
+ 
+    /* Compute and store error */ 
+    d = (float32_t) (*pRef++); 
+    e = d - sum; 
+    *pErr++ = e; 
+ 
+    /* Calculation of Weighting factor for updating filter coefficients */ 
+    /* epsilon value 0.000000119209289f */ 
+    w = (e * mu) / (energy + 0.000000119209289f); 
+ 
+    /* Initialize pState pointer */ 
+    px = pState; 
+ 
+    /* Initialize coeff pointer */ 
+    pb = (pCoeffs); 
+ 
+    /* Loop unrolling.  Process 4 taps at a time. */ 
+    tapCnt = numTaps >> 2; 
+ 
+    /* Update filter coefficients */ 
+    while(tapCnt > 0u) 
+    { 
+      /* Perform the multiply-accumulate */ 
+      *pb += w * (*px++); 
+      pb++; 
+ 
+      *pb += w * (*px++); 
+      pb++; 
+ 
+      *pb += w * (*px++); 
+      pb++; 
+ 
+      *pb += w * (*px++); 
+      pb++; 
+ 
+ 
+      /* Decrement the loop counter */ 
+      tapCnt--; 
+    } 
+ 
+    /* If the filter length is not a multiple of 4, compute the remaining filter taps */ 
+    tapCnt = numTaps % 0x4u; 
+ 
+    while(tapCnt > 0u) 
+    { 
+      /* Perform the multiply-accumulate */ 
+      *pb += w * (*px++); 
+      pb++; 
+ 
+      /* Decrement the loop counter */ 
+      tapCnt--; 
+    } 
+ 
+    x0 = *pState; 
+ 
+    /* Advance state pointer by 1 for the next sample */ 
+    pState = pState + 1; 
+ 
+    /* Decrement the loop counter */ 
+    blkCnt--; 
+  } 
+ 
+  S->energy = energy; 
+  S->x0 = x0; 
+ 
+  /* Processing is complete. Now copy the last numTaps - 1 samples to the  
+     satrt of the state buffer. This prepares the state buffer for the  
+     next function call. */ 
+ 
+  /* Points to the start of the pState buffer */ 
+  pStateCurnt = S->pState; 
+ 
+  /* Loop unrolling for (numTaps - 1u)/4 samples copy */ 
+  tapCnt = (numTaps - 1u) >> 2u; 
+ 
+  /* copy data */ 
+  while(tapCnt > 0u) 
+  { 
+    *pStateCurnt++ = *pState++; 
+    *pStateCurnt++ = *pState++; 
+    *pStateCurnt++ = *pState++; 
+    *pStateCurnt++ = *pState++; 
+ 
+    /* Decrement the loop counter */ 
+    tapCnt--; 
+  } 
+ 
+  /* Calculate remaining number of copies */ 
+  tapCnt = (numTaps - 1u) % 0x4u; 
+ 
+  /* Copy the remaining q31_t data */ 
+  while(tapCnt > 0u) 
+  { 
+    *pStateCurnt++ = *pState++; 
+ 
+    /* Decrement the loop counter */ 
+    tapCnt--; 
+  } 
+ 
+ 
+} 
+ 
+/**  
+   * @} end of LMS_NORM group  
+   */