67 lines
2.2 KiB
C
67 lines
2.2 KiB
C
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/* -*- mode: c; tab-width: 4; indent-tabs-mode: t; c-basic-offset: 4; coding: utf-8 -*- */
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/************************************************************************************
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** **
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** UHSDR **
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** a powerful firmware for STM32 based SDR transceivers **
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** **
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**---------------------------------------------------------------------------------**
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** **
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** Licence: GNU GPLv3 **
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************************************************************************************/
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#include <malloc.h>
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#include <string.h>
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#include <assert.h>
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#include "uhsdr_math.h"
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/**
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* Fast algorithm for log10
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*
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* This is a fast approximation to log2()
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* Y = C[0]*F*F*F + C[1]*F*F + C[2]*F + C[3] + E;
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* log10f is exactly log2(x)/log2(10.0f)
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* Math_log10f_fast(x) =(log2f_approx(x)*0.3010299956639812f)
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*
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* @param X number want log10 for
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* @return log10(x)
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*/
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float32_t Math_log10f_fast(float32_t X) {
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float Y, F;
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int E;
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F = frexpf(fabsf(X), &E);
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Y = 1.23149591368684f;
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Y *= F;
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Y += -4.11852516267426f;
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Y *= F;
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Y += 6.02197014179219f;
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Y *= F;
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Y += -3.13396450166353f;
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Y += E;
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return(Y * 0.3010299956639812f);
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}
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/**
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* Find the absolute (i.e. ignoring the sign) maximum value
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* @param float32_t buffer to be searched
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* @param size how many elements
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* @return the actual maxium value of the size elements in buffer
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*/
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float32_t Math_absmax(float32_t* buffer, int size)
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{
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float32_t min, max;
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uint32_t pindex;
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arm_max_f32(buffer, size, &max, &pindex); // find absolute value of audio in buffer after gain applied
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arm_min_f32(buffer, size, &min, &pindex);
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return -min>max?-min:max;
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}
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/**
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* get the sign of a float number
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* @param x the number to test
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* @return -1 if below zero, 0 if zero, 1 if above zero
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*/
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float32_t Math_sign_new (float32_t x) {
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return (x < 0) ? -1.0 : ( (x > 0) ? 1.0 : 0.0);
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}
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