audio_FFT - Read an audio signal from the ADC, write it out t…

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James Cobb / Mbed 2 deprecated audio_FFT

Read an audio signal from the ADC, write it out to a file on the filestytem and perform a 1024 point FFT, writing frequency data to a csv file

Dependencies: mbed

main.cpp@0:5b7b619f59cd, 2010-03-21 (annotated)

Committer:: jcobb
Date:: Sun Mar 21 18:06:46 2010 +0000
Revision:: 0:5b7b619f59cd

Who changed what in which revision?

User	Revision	Line number	New contents of line
jcobb	0:5b7b619f59cd	1
jcobb	0:5b7b619f59cd	2	#define SAMPLE_RATE 48000
jcobb	0:5b7b619f59cd	3
jcobb	0:5b7b619f59cd	4	#include "mbed.h"
jcobb	0:5b7b619f59cd	5	#include "adc.h"
jcobb	0:5b7b619f59cd	6
jcobb	0:5b7b619f59cd	7	//Going to use the Mellen FFT rather than STM, as the STM (port by Igor) won't compile
jcobb	0:5b7b619f59cd	8	//extern "C" void cr4_fft_256_stm32(void pssOUT, void pssIN, uint16_t Nbin);
jcobb	0:5b7b619f59cd	9	extern "C" void fftR4(short y, short x, int N);
jcobb	0:5b7b619f59cd	10
jcobb	0:5b7b619f59cd	11	//use the LED as a bargraph
jcobb	0:5b7b619f59cd	12	DigitalOut l1(LED1);
jcobb	0:5b7b619f59cd	13	DigitalOut l2(LED2);
jcobb	0:5b7b619f59cd	14	DigitalOut l3(LED3);
jcobb	0:5b7b619f59cd	15	DigitalOut l4(LED4);
jcobb	0:5b7b619f59cd	16
jcobb	0:5b7b619f59cd	17	//set up a timer for timing FFT's
jcobb	0:5b7b619f59cd	18	Timer timer;
jcobb	0:5b7b619f59cd	19
jcobb	0:5b7b619f59cd	20	//Set up filesystem so we can write some useful files
jcobb	0:5b7b619f59cd	21
jcobb	0:5b7b619f59cd	22	LocalFileSystem local("local");
jcobb	0:5b7b619f59cd	23	FILE *fp;
jcobb	0:5b7b619f59cd	24
jcobb	0:5b7b619f59cd	25	//Set up a global buffer for audio data so interrupt can access it
jcobb	0:5b7b619f59cd	26	int Counter = 0;
jcobb	0:5b7b619f59cd	27	int16_t Buffer[5000];
jcobb	0:5b7b619f59cd	28
jcobb	0:5b7b619f59cd	29	//Initialise ADC to maximum SAMPLE_RATE and cclk divide set to 1
jcobb	0:5b7b619f59cd	30	ADC adc(SAMPLE_RATE, 1);
jcobb	0:5b7b619f59cd	31
jcobb	0:5b7b619f59cd	32	//Functions to write 16 bit audio data and 32 bit headers to files in au format (cf sndRecorder Cookbook)
jcobb	0:5b7b619f59cd	33	void fwrite16(uint16_t v)
jcobb	0:5b7b619f59cd	34	{
jcobb	0:5b7b619f59cd	35	uint8_t b = (uint8_t )&v;
jcobb	0:5b7b619f59cd	36
jcobb	0:5b7b619f59cd	37	fprintf(fp,"%c%c", b[1], b[0]);
jcobb	0:5b7b619f59cd	38	}
jcobb	0:5b7b619f59cd	39	void fwrite32(uint32_t v)
jcobb	0:5b7b619f59cd	40	{
jcobb	0:5b7b619f59cd	41	uint8_t b = (uint8_t )&v;
jcobb	0:5b7b619f59cd	42
jcobb	0:5b7b619f59cd	43	fprintf(fp,"%c%c%c%c", b[3], b[2], b[1], b[0]);
jcobb	0:5b7b619f59cd	44	}
jcobb	0:5b7b619f59cd	45
jcobb	0:5b7b619f59cd	46	//Our interrupt handler for audio sampling
jcobb	0:5b7b619f59cd	47	void sample_ADC(int chan, uint32_t value) {
jcobb	0:5b7b619f59cd	48
jcobb	0:5b7b619f59cd	49	float s;
jcobb	0:5b7b619f59cd	50	s = adc.read(p20);
jcobb	0:5b7b619f59cd	51	int16_t b = (s -2048)*16;
jcobb	0:5b7b619f59cd	52	Buffer[Counter] = b;
jcobb	0:5b7b619f59cd	53	Counter += 1;
jcobb	0:5b7b619f59cd	54	/* bar graph */
jcobb	0:5b7b619f59cd	55	int g = abs(s-2048);
jcobb	0:5b7b619f59cd	56	l1 = g > 0.1f*2048;
jcobb	0:5b7b619f59cd	57	l2 = g > 0.3f*2048;
jcobb	0:5b7b619f59cd	58	l3 = g > 0.6f*2048;
jcobb	0:5b7b619f59cd	59	l4 = g > 0.8f*2048;
jcobb	0:5b7b619f59cd	60	}
jcobb	0:5b7b619f59cd	61
jcobb	0:5b7b619f59cd	62	int main() {
jcobb	0:5b7b619f59cd	63
jcobb	0:5b7b619f59cd	64	//Prepare for burst mode on all ADC pins and set up interrupt handler (using ADC library from Simon Blandford
jcobb	0:5b7b619f59cd	65	adc.append(sample_ADC);
jcobb	0:5b7b619f59cd	66	adc.startmode(0,0);
jcobb	0:5b7b619f59cd	67	adc.burst(1);
jcobb	0:5b7b619f59cd	68	adc.setup(p20,1);
jcobb	0:5b7b619f59cd	69
jcobb	0:5b7b619f59cd	70	//introduce a delay as initial waveform has bias whilst decoupling cap charges
jcobb	0:5b7b619f59cd	71	wait(1);
jcobb	0:5b7b619f59cd	72
jcobb	0:5b7b619f59cd	73	//start the interrupt and wait for about 4096 samples
jcobb	0:5b7b619f59cd	74	adc.interrupt_state(p20,1);
jcobb	0:5b7b619f59cd	75	wait(0.1);
jcobb	0:5b7b619f59cd	76
jcobb	0:5b7b619f59cd	77	//Finsh up - Unset pin 20
jcobb	0:5b7b619f59cd	78	adc.interrupt_state(p20,0);
jcobb	0:5b7b619f59cd	79	adc.setup(p20,0);
jcobb	0:5b7b619f59cd	80	int actual_rate = adc.actual_sample_rate();
jcobb	0:5b7b619f59cd	81
jcobb	0:5b7b619f59cd	82	//for debugging tell the terminal sample rate and how many samples we took
jcobb	0:5b7b619f59cd	83	printf("Requested max sample rate is %u, actual max sample rate is %u.\n",
jcobb	0:5b7b619f59cd	84	SAMPLE_RATE, actual_rate);
jcobb	0:5b7b619f59cd	85	printf("We did %i samples\n",Counter);
jcobb	0:5b7b619f59cd	86
jcobb	0:5b7b619f59cd	87	//write original audio file to filesytem so we can load on PC and see what's there (cf sndRecorder Cookbook)
jcobb	0:5b7b619f59cd	88	fp = fopen("/local/out.au", "w");
jcobb	0:5b7b619f59cd	89	fprintf(fp,".snd");
jcobb	0:5b7b619f59cd	90	fwrite32(24);
jcobb	0:5b7b619f59cd	91	fwrite32(-1);
jcobb	0:5b7b619f59cd	92	fwrite32(3);
jcobb	0:5b7b619f59cd	93	fwrite32(48000);
jcobb	0:5b7b619f59cd	94	fwrite32(1);
jcobb	0:5b7b619f59cd	95	int writeCount = 0;
jcobb	0:5b7b619f59cd	96	while(writeCount <=Counter) {
jcobb	0:5b7b619f59cd	97	fwrite16(Buffer[writeCount]);
jcobb	0:5b7b619f59cd	98	writeCount+=1;
jcobb	0:5b7b619f59cd	99	}
jcobb	0:5b7b619f59cd	100
jcobb	0:5b7b619f59cd	101	//Not using the STM FFT, but leave code here for the moment
jcobb	0:5b7b619f59cd	102
jcobb	0:5b7b619f59cd	103	/*
jcobb	0:5b7b619f59cd	104	//now do a fft of the initial 1024 samples
jcobb	0:5b7b619f59cd	105	#define N 256 //Number of points
jcobb	0:5b7b619f59cd	106	uint32_t x[N], y[N]; // input and output arrays
jcobb	0:5b7b619f59cd	107	int16_t real[N], imag[N]; // real and imaginary arrays
jcobb	0:5b7b619f59cd	108	memset(real, 0, sizeof(real));
jcobb	0:5b7b619f59cd	109	memset(imag, 0, sizeof(imag));
jcobb	0:5b7b619f59cd	110	// real[1]=SHRT_MAX;
jcobb	0:5b7b619f59cd	111	// Fill the input array
jcobb	0:5b7b619f59cd	112	for (int i=0; i<N; i++)
jcobb	0:5b7b619f59cd	113	{
jcobb	0:5b7b619f59cd	114	x[i] = (((uint16_t)(Buffer[i])) \| ((uint32_t)(0<<16)));
jcobb	0:5b7b619f59cd	115	}
jcobb	0:5b7b619f59cd	116	timer.reset();
jcobb	0:5b7b619f59cd	117	timer.start();
jcobb	0:5b7b619f59cd	118	cr4_fft_256_stm32(y, x, N); //computes the FFT of the x[N] samples
jcobb	0:5b7b619f59cd	119	printf("ST32 fft up took %i\n",timer.read_us());
jcobb	0:5b7b619f59cd	120	FILE* log = fopen("/local/stm32.txt","w");
jcobb	0:5b7b619f59cd	121	for (int i=0; i<N; i++)
jcobb	0:5b7b619f59cd	122	{
jcobb	0:5b7b619f59cd	123	fprintf(log, "%d: %d, %d -> %d, %d\n", i, Buffer[i], 0 , int16_t(y[i] & 0xFFFF), int16_t(y[i] >> 16));
jcobb	0:5b7b619f59cd	124	}
jcobb	0:5b7b619f59cd	125	fclose(log);
jcobb	0:5b7b619f59cd	126
jcobb	0:5b7b619f59cd	127	//compute frequencies and magnitudes of result
jcobb	0:5b7b619f59cd	128	FILE* spectrum = fopen("/local/stm32Spec.txt","w");
jcobb	0:5b7b619f59cd	129	for (int i=0; i<N/2; i++)
jcobb	0:5b7b619f59cd	130	{
jcobb	0:5b7b619f59cd	131	float real = int16_t(y[i] & 0xFFFF)* int16_t(y[i] & 0xFFFF);
jcobb	0:5b7b619f59cd	132	float imag = int16_t(y[i] >> 16)* int16_t(y[i] >> 16);
jcobb	0:5b7b619f59cd	133	fprintf(spectrum, "%d -> %f\n", int(SAMPLE_RATE/N*i),sqrt(imag+real));
jcobb	0:5b7b619f59cd	134	}
jcobb	0:5b7b619f59cd	135	fclose(spectrum);
jcobb	0:5b7b619f59cd	136	*/
jcobb	0:5b7b619f59cd	137
jcobb	0:5b7b619f59cd	138	//now lets try mellen fft
jcobb	0:5b7b619f59cd	139	timer.reset();
jcobb	0:5b7b619f59cd	140	timer.start();
jcobb	0:5b7b619f59cd	141	#define MN 1024 /Number of points/
jcobb	0:5b7b619f59cd	142	short mx[MN*2]; // input data 16 bit, 4 byte aligned x0r,x0i,x1r,x1i,....
jcobb	0:5b7b619f59cd	143	short my[MN*2]; // output data 16 bit,4 byte aligned y0r,y0i,y1r,y1i,....
jcobb	0:5b7b619f59cd	144	for (int i=0;i<MN*2;i++) mx[i]=0;
jcobb	0:5b7b619f59cd	145	for (int i=0;i<MN;i=i+1)
jcobb	0:5b7b619f59cd	146	{ mx[i*2]=Buffer[i];}
jcobb	0:5b7b619f59cd	147	printf("Mellen set up took %i\n",timer.read_us());
jcobb	0:5b7b619f59cd	148	//call functions
jcobb	0:5b7b619f59cd	149	timer.reset();
jcobb	0:5b7b619f59cd	150	timer.start();
jcobb	0:5b7b619f59cd	151	fftR4(my, mx, MN);
jcobb	0:5b7b619f59cd	152	printf("Mellen fft took %i\n",timer.read_us());
jcobb	0:5b7b619f59cd	153	FILE* mlog = fopen("/local/mellen.csv","w");
jcobb	0:5b7b619f59cd	154
jcobb	0:5b7b619f59cd	155	//now write a CSV file to filesytem of frequency vs amplitude
jcobb	0:5b7b619f59cd	156	for (int i=0; i<MN; i=i+2)
jcobb	0:5b7b619f59cd	157	{
jcobb	0:5b7b619f59cd	158	// fprintf(mlog, "%d: %d -> %d\n", i, mx[i], my[i]);
jcobb	0:5b7b619f59cd	159	fprintf(mlog, "%d,%f\n", int(actual_rate/MN/2i),sqrt(float( (my[i]my[i]) +(my[i+1]*my[i+1]) ) ) );
jcobb	0:5b7b619f59cd	160	}
jcobb	0:5b7b619f59cd	161	fclose(mlog);
jcobb	0:5b7b619f59cd	162
jcobb	0:5b7b619f59cd	163
jcobb	0:5b7b619f59cd	164	}
jcobb	0:5b7b619f59cd	165
jcobb	0:5b7b619f59cd	166
jcobb	0:5b7b619f59cd	167
jcobb	0:5b7b619f59cd	168
jcobb	0:5b7b619f59cd	169

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Type:	Program
Mbed OS support:	Mbed 2 deprecated
Created:	21 Mar 2010
Imports:	810
Forks:	1
Commits:	1
Dependents:	0
Dependencies:	1
Followers:	23

main.cpp@0:5b7b619f59cd, 2010-03-21 (annotated)

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