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479 lines
13 KiB
C++
479 lines
13 KiB
C++
#include <cstdint>
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using float32_t = float;
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typedef struct
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{
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uint16_t numTaps; /**< number of filter coefficients in the filter. */
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float32_t *pState; /**< points to the state variable array. The array is of length numTaps+blockSize-1. */
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float32_t *pCoeffs; /**< points to the coefficient array. The array is of length numTaps. */
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} arm_fir_instance_f32;
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static void arm_fir_f32(const arm_fir_instance_f32 * S, float32_t * pSrc, float32_t * pDst, uint32_t blockSize);
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Sample *process_data(Samples samples)
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{
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// 1. Define our array sizes (Be sure to set Run > Set buffer size... to below value!)
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constexpr unsigned int buffer_size = 500;
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constexpr unsigned int filter_size = 100;
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// 2. Define our filter and the working arrays
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static float filter[filter_size] = {
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.01f,.01f,.01f,.01f,.01f,.01f,.01f,.01f,.01f,.01f,
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.01f,.01f,.01f,.01f,.01f,.01f,.01f,.01f,.01f,.01f,
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.01f,.01f,.01f,.01f,.01f,.01f,.01f,.01f,.01f,.01f,
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.01f,.01f,.01f,.01f,.01f,.01f,.01f,.01f,.01f,.01f,
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.01f,.01f,.01f,.01f,.01f,.01f,.01f,.01f,.01f,.01f,
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.01f,.01f,.01f,.01f,.01f,.01f,.01f,.01f,.01f,.01f,
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.01f,.01f,.01f,.01f,.01f,.01f,.01f,.01f,.01f,.01f,
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.01f,.01f,.01f,.01f,.01f,.01f,.01f,.01f,.01f,.01f,
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.01f,.01f,.01f,.01f,.01f,.01f,.01f,.01f,.01f,.01f,
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.01f,.01f,.01f,.01f,.01f,.01f,.01f,.01f,.01f,.01f
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};
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static float input[buffer_size];
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static float output[buffer_size];
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static float working[buffer_size + filter_size];
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// 3. Scale 0-4095 interger sample values to +/- 1.0 floats
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for (unsigned int i = 0; i < samples.size(); i++)
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input[i] = (samples[i] - 2048) / 2048.f;
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// 4. Compute the FIR
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arm_fir_instance_f32 fir { filter_size, working, filter };
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arm_fir_f32(&fir, input, output, samples.size());
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// 5. Convert float results back to 0-4095 range for output
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for (unsigned int i = 0; i < samples.size(); i++)
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samples[i] = output[i] * 2048.f + 2048;
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return samples.data();
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}
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// Below taken from the CMSIS DSP Library (find it on GitHub)
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void arm_fir_f32(
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const arm_fir_instance_f32 * S,
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float32_t * pSrc,
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float32_t * pDst,
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uint32_t blockSize)
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{
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float32_t *pState = S->pState; /* State pointer */
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float32_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
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float32_t *pStateCurnt; /* Points to the current sample of the state */
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float32_t *px, *pb; /* Temporary pointers for state and coefficient buffers */
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float32_t acc0, acc1, acc2, acc3, acc4, acc5, acc6, acc7; /* Accumulators */
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float32_t x0, x1, x2, x3, x4, x5, x6, x7, c0; /* Temporary variables to hold state and coefficient values */
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uint32_t numTaps = S->numTaps; /* Number of filter coefficients in the filter */
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uint32_t i, tapCnt, blkCnt; /* Loop counters */
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float32_t p0,p1,p2,p3,p4,p5,p6,p7; /* Temporary product values */
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/* S->pState points to state array which contains previous frame (numTaps - 1) samples */
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/* pStateCurnt points to the location where the new input data should be written */
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pStateCurnt = &(S->pState[(numTaps - 1u)]);
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/* Apply loop unrolling and compute 8 output values simultaneously.
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* The variables acc0 ... acc7 hold output values that are being computed:
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*
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* acc0 = b[numTaps-1] * x[n-numTaps-1] + b[numTaps-2] * x[n-numTaps-2] + b[numTaps-3] * x[n-numTaps-3] +...+ b[0] * x[0]
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* acc1 = b[numTaps-1] * x[n-numTaps] + b[numTaps-2] * x[n-numTaps-1] + b[numTaps-3] * x[n-numTaps-2] +...+ b[0] * x[1]
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* acc2 = b[numTaps-1] * x[n-numTaps+1] + b[numTaps-2] * x[n-numTaps] + b[numTaps-3] * x[n-numTaps-1] +...+ b[0] * x[2]
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* acc3 = b[numTaps-1] * x[n-numTaps+2] + b[numTaps-2] * x[n-numTaps+1] + b[numTaps-3] * x[n-numTaps] +...+ b[0] * x[3]
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*/
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blkCnt = blockSize >> 3;
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/* First part of the processing with loop unrolling. Compute 8 outputs at a time.
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** a second loop below computes the remaining 1 to 7 samples. */
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while(blkCnt > 0u)
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{
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/* Copy four new input samples into the state buffer */
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*pStateCurnt++ = *pSrc++;
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*pStateCurnt++ = *pSrc++;
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*pStateCurnt++ = *pSrc++;
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*pStateCurnt++ = *pSrc++;
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/* Set all accumulators to zero */
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acc0 = 0.0f;
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acc1 = 0.0f;
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acc2 = 0.0f;
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acc3 = 0.0f;
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acc4 = 0.0f;
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acc5 = 0.0f;
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acc6 = 0.0f;
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acc7 = 0.0f;
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/* Initialize state pointer */
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px = pState;
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/* Initialize coeff pointer */
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pb = (pCoeffs);
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/* This is separated from the others to avoid
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* a call to __aeabi_memmove which would be slower
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*/
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*pStateCurnt++ = *pSrc++;
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*pStateCurnt++ = *pSrc++;
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*pStateCurnt++ = *pSrc++;
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*pStateCurnt++ = *pSrc++;
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/* Read the first seven samples from the state buffer: x[n-numTaps], x[n-numTaps-1], x[n-numTaps-2] */
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x0 = *px++;
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x1 = *px++;
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x2 = *px++;
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x3 = *px++;
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x4 = *px++;
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x5 = *px++;
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x6 = *px++;
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/* Loop unrolling. Process 8 taps at a time. */
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tapCnt = numTaps >> 3u;
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/* Loop over the number of taps. Unroll by a factor of 8.
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** Repeat until we've computed numTaps-8 coefficients. */
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while(tapCnt > 0u)
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{
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/* Read the b[numTaps-1] coefficient */
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c0 = *(pb++);
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/* Read x[n-numTaps-3] sample */
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x7 = *(px++);
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/* acc0 += b[numTaps-1] * x[n-numTaps] */
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p0 = x0 * c0;
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/* acc1 += b[numTaps-1] * x[n-numTaps-1] */
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p1 = x1 * c0;
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/* acc2 += b[numTaps-1] * x[n-numTaps-2] */
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p2 = x2 * c0;
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/* acc3 += b[numTaps-1] * x[n-numTaps-3] */
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p3 = x3 * c0;
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/* acc4 += b[numTaps-1] * x[n-numTaps-4] */
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p4 = x4 * c0;
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/* acc1 += b[numTaps-1] * x[n-numTaps-5] */
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p5 = x5 * c0;
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/* acc2 += b[numTaps-1] * x[n-numTaps-6] */
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p6 = x6 * c0;
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/* acc3 += b[numTaps-1] * x[n-numTaps-7] */
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p7 = x7 * c0;
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/* Read the b[numTaps-2] coefficient */
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c0 = *(pb++);
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/* Read x[n-numTaps-4] sample */
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x0 = *(px++);
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acc0 += p0;
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acc1 += p1;
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acc2 += p2;
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acc3 += p3;
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acc4 += p4;
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acc5 += p5;
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acc6 += p6;
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acc7 += p7;
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/* Perform the multiply-accumulate */
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p0 = x1 * c0;
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p1 = x2 * c0;
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p2 = x3 * c0;
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p3 = x4 * c0;
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p4 = x5 * c0;
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p5 = x6 * c0;
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p6 = x7 * c0;
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p7 = x0 * c0;
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/* Read the b[numTaps-3] coefficient */
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c0 = *(pb++);
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/* Read x[n-numTaps-5] sample */
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x1 = *(px++);
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acc0 += p0;
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acc1 += p1;
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acc2 += p2;
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acc3 += p3;
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acc4 += p4;
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acc5 += p5;
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acc6 += p6;
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acc7 += p7;
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/* Perform the multiply-accumulates */
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p0 = x2 * c0;
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p1 = x3 * c0;
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p2 = x4 * c0;
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p3 = x5 * c0;
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p4 = x6 * c0;
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p5 = x7 * c0;
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p6 = x0 * c0;
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p7 = x1 * c0;
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/* Read the b[numTaps-4] coefficient */
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c0 = *(pb++);
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/* Read x[n-numTaps-6] sample */
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x2 = *(px++);
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acc0 += p0;
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acc1 += p1;
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acc2 += p2;
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acc3 += p3;
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acc4 += p4;
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acc5 += p5;
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acc6 += p6;
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acc7 += p7;
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/* Perform the multiply-accumulates */
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p0 = x3 * c0;
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p1 = x4 * c0;
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p2 = x5 * c0;
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p3 = x6 * c0;
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p4 = x7 * c0;
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p5 = x0 * c0;
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p6 = x1 * c0;
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p7 = x2 * c0;
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/* Read the b[numTaps-4] coefficient */
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c0 = *(pb++);
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/* Read x[n-numTaps-6] sample */
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x3 = *(px++);
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acc0 += p0;
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acc1 += p1;
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acc2 += p2;
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acc3 += p3;
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acc4 += p4;
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acc5 += p5;
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acc6 += p6;
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acc7 += p7;
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/* Perform the multiply-accumulates */
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p0 = x4 * c0;
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p1 = x5 * c0;
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p2 = x6 * c0;
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p3 = x7 * c0;
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p4 = x0 * c0;
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p5 = x1 * c0;
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p6 = x2 * c0;
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p7 = x3 * c0;
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/* Read the b[numTaps-4] coefficient */
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c0 = *(pb++);
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/* Read x[n-numTaps-6] sample */
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x4 = *(px++);
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acc0 += p0;
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acc1 += p1;
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acc2 += p2;
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acc3 += p3;
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acc4 += p4;
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acc5 += p5;
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acc6 += p6;
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acc7 += p7;
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/* Perform the multiply-accumulates */
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p0 = x5 * c0;
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p1 = x6 * c0;
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p2 = x7 * c0;
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p3 = x0 * c0;
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p4 = x1 * c0;
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p5 = x2 * c0;
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p6 = x3 * c0;
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p7 = x4 * c0;
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/* Read the b[numTaps-4] coefficient */
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c0 = *(pb++);
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/* Read x[n-numTaps-6] sample */
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x5 = *(px++);
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acc0 += p0;
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acc1 += p1;
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acc2 += p2;
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acc3 += p3;
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acc4 += p4;
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acc5 += p5;
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acc6 += p6;
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acc7 += p7;
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/* Perform the multiply-accumulates */
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p0 = x6 * c0;
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p1 = x7 * c0;
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p2 = x0 * c0;
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p3 = x1 * c0;
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p4 = x2 * c0;
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p5 = x3 * c0;
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p6 = x4 * c0;
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p7 = x5 * c0;
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/* Read the b[numTaps-4] coefficient */
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c0 = *(pb++);
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/* Read x[n-numTaps-6] sample */
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x6 = *(px++);
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acc0 += p0;
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acc1 += p1;
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acc2 += p2;
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acc3 += p3;
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acc4 += p4;
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acc5 += p5;
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acc6 += p6;
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acc7 += p7;
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/* Perform the multiply-accumulates */
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p0 = x7 * c0;
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p1 = x0 * c0;
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p2 = x1 * c0;
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p3 = x2 * c0;
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p4 = x3 * c0;
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p5 = x4 * c0;
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p6 = x5 * c0;
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p7 = x6 * c0;
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tapCnt--;
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acc0 += p0;
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acc1 += p1;
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acc2 += p2;
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acc3 += p3;
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acc4 += p4;
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acc5 += p5;
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acc6 += p6;
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acc7 += p7;
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}
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/* If the filter length is not a multiple of 8, compute the remaining filter taps */
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tapCnt = numTaps % 0x8u;
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while(tapCnt > 0u)
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{
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/* Read coefficients */
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c0 = *(pb++);
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/* Fetch 1 state variable */
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x7 = *(px++);
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/* Perform the multiply-accumulates */
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p0 = x0 * c0;
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p1 = x1 * c0;
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p2 = x2 * c0;
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p3 = x3 * c0;
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p4 = x4 * c0;
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p5 = x5 * c0;
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p6 = x6 * c0;
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p7 = x7 * c0;
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/* Reuse the present sample states for next sample */
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x0 = x1;
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x1 = x2;
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x2 = x3;
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x3 = x4;
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x4 = x5;
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x5 = x6;
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x6 = x7;
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acc0 += p0;
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acc1 += p1;
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acc2 += p2;
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acc3 += p3;
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acc4 += p4;
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acc5 += p5;
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acc6 += p6;
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acc7 += p7;
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/* Decrement the loop counter */
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tapCnt--;
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}
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/* Advance the state pointer by 8 to process the next group of 8 samples */
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pState = pState + 8;
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/* The results in the 8 accumulators, store in the destination buffer. */
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*pDst++ = acc0;
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*pDst++ = acc1;
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*pDst++ = acc2;
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*pDst++ = acc3;
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*pDst++ = acc4;
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*pDst++ = acc5;
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*pDst++ = acc6;
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*pDst++ = acc7;
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blkCnt--;
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}
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/* If the blockSize is not a multiple of 8, compute any remaining output samples here.
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** No loop unrolling is used. */
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blkCnt = blockSize % 0x8u;
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while(blkCnt > 0u)
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{
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/* Copy one sample at a time into state buffer */
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*pStateCurnt++ = *pSrc++;
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/* Set the accumulator to zero */
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acc0 = 0.0f;
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/* Initialize state pointer */
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px = pState;
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/* Initialize Coefficient pointer */
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pb = (pCoeffs);
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i = numTaps;
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/* Perform the multiply-accumulates */
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do
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{
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acc0 += *px++ * *pb++;
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i--;
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} while(i > 0u);
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/* The result is store in the destination buffer. */
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*pDst++ = acc0;
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/* Advance state pointer by 1 for the next sample */
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pState = pState + 1;
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blkCnt--;
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}
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/* Processing is complete.
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** Now copy the last numTaps - 1 samples to the start of the state buffer.
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** This prepares the state buffer for the next function call. */
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/* Points to the start of the state buffer */
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pStateCurnt = S->pState;
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tapCnt = (numTaps - 1u) >> 2u;
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/* copy data */
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while(tapCnt > 0u)
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{
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*pStateCurnt++ = *pState++;
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*pStateCurnt++ = *pState++;
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*pStateCurnt++ = *pState++;
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*pStateCurnt++ = *pState++;
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/* Decrement the loop counter */
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tapCnt--;
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}
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/* Calculate remaining number of copies */
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tapCnt = (numTaps - 1u) % 0x4u;
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/* Copy the remaining q31_t data */
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while(tapCnt > 0u)
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{
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*pStateCurnt++ = *pState++;
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/* Decrement the loop counter */
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tapCnt--;
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}
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}
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