SpectrumAnalyzer - This is a simple program that displays a spectrum…

Users » gth646f » Code » SpectrumAnalyzer

Elliot Hernandez / Mbed 2 deprecated SpectrumAnalyzer

This is a simple program that displays a spectrum analyzer on the Nokia LCD from an input through a 3.5mm audio jack. It uses FFT\'s to compute the fourier transform of the incoming audio signal and display the amplitudes across the screen at the different frequencies.

Dependencies: mbed NokiaLCD

main.cpp@0:b6451e68016a, 2011-02-28 (annotated)

Committer:: gth646f
Date:: Mon Feb 28 03:26:53 2011 +0000
Revision:: 0:b6451e68016a

Who changed what in which revision?

User	Revision	Line number	New contents of line
gth646f	0:b6451e68016a	1
gth646f	0:b6451e68016a	2
gth646f	0:b6451e68016a	3
gth646f	0:b6451e68016a	4
gth646f	0:b6451e68016a	5	#include "mbed.h"
gth646f	0:b6451e68016a	6	#include "adc.h"
gth646f	0:b6451e68016a	7	#include "NokiaLCD.h"
gth646f	0:b6451e68016a	8
gth646f	0:b6451e68016a	9	#define MN 256 /Number of points/
gth646f	0:b6451e68016a	10	#define SAMPLE_RATE 48000
gth646f	0:b6451e68016a	11	NokiaLCD lcd(p5, p7, p8, p9, NokiaLCD::LCD6610); // mosi, sclk, cs, rst, type
gth646f	0:b6451e68016a	12
gth646f	0:b6451e68016a	13
gth646f	0:b6451e68016a	14	//Going to use the Mellen FFT rather than STM, as the STM (port by Igor) won't compile
gth646f	0:b6451e68016a	15	//extern "C" void cr4_fft_256_stm32(void pssOUT, void pssIN, uint16_t Nbin);
gth646f	0:b6451e68016a	16	extern "C" void fftR4(short y, short x, int N);
gth646f	0:b6451e68016a	17
gth646f	0:b6451e68016a	18	//use the LED as a bargraph
gth646f	0:b6451e68016a	19	DigitalOut l1(LED1);
gth646f	0:b6451e68016a	20	DigitalOut l2(LED2);
gth646f	0:b6451e68016a	21	DigitalOut l3(LED3);
gth646f	0:b6451e68016a	22	DigitalOut l4(LED4);
gth646f	0:b6451e68016a	23
gth646f	0:b6451e68016a	24	//set up a timer for timing FFT's
gth646f	0:b6451e68016a	25	Timer timer;
gth646f	0:b6451e68016a	26	Ticker ticker;
gth646f	0:b6451e68016a	27
gth646f	0:b6451e68016a	28	//Set up filesystem so we can write some useful files
gth646f	0:b6451e68016a	29	LocalFileSystem local("local");
gth646f	0:b6451e68016a	30	FILE *fp;
gth646f	0:b6451e68016a	31
gth646f	0:b6451e68016a	32
gth646f	0:b6451e68016a	33	//Set up a global buffer for audio data so interrupt can access it
gth646f	0:b6451e68016a	34	int Counter = 0;
gth646f	0:b6451e68016a	35	int16_t Buffer[5000];
gth646f	0:b6451e68016a	36
gth646f	0:b6451e68016a	37
gth646f	0:b6451e68016a	38	//Initialise ADC to maximum SAMPLE_RATE and cclk divide set to 1
gth646f	0:b6451e68016a	39	ADC adc(SAMPLE_RATE, 1);
gth646f	0:b6451e68016a	40
gth646f	0:b6451e68016a	41	//Functions to write 16 bit audio data and 32 bit headers to files in au format (cf sndRecorder Cookbook)
gth646f	0:b6451e68016a	42	void fwrite16(uint16_t v) {
gth646f	0:b6451e68016a	43	uint8_t b = (uint8_t )&v;
gth646f	0:b6451e68016a	44
gth646f	0:b6451e68016a	45	fprintf(fp,"%c%c", b[1], b[0]);
gth646f	0:b6451e68016a	46	}
gth646f	0:b6451e68016a	47	void fwrite32(uint32_t v) {
gth646f	0:b6451e68016a	48	uint8_t b = (uint8_t )&v;
gth646f	0:b6451e68016a	49
gth646f	0:b6451e68016a	50	fprintf(fp,"%c%c%c%c", b[3], b[2], b[1], b[0]);
gth646f	0:b6451e68016a	51	}
gth646f	0:b6451e68016a	52
gth646f	0:b6451e68016a	53
gth646f	0:b6451e68016a	54
gth646f	0:b6451e68016a	55	//Our interrupt handler for audio sampling
gth646f	0:b6451e68016a	56	void sample_ADC(int chan, uint32_t value) {
gth646f	0:b6451e68016a	57
gth646f	0:b6451e68016a	58	float s;
gth646f	0:b6451e68016a	59	s = adc.read(p20);
gth646f	0:b6451e68016a	60	int16_t b = (s -2048)*16;
gth646f	0:b6451e68016a	61	Buffer[Counter] = b;
gth646f	0:b6451e68016a	62	Counter += 1;
gth646f	0:b6451e68016a	63	/* bar graph */
gth646f	0:b6451e68016a	64	int g = abs(s-2048);
gth646f	0:b6451e68016a	65	l1 = g > 0.1f*2048;
gth646f	0:b6451e68016a	66	l2 = g > 0.3f*2048;
gth646f	0:b6451e68016a	67	l3 = g > 0.6f*2048;
gth646f	0:b6451e68016a	68	l4 = g > 0.8f*2048;
gth646f	0:b6451e68016a	69	}
gth646f	0:b6451e68016a	70
gth646f	0:b6451e68016a	71	int main() {
gth646f	0:b6451e68016a	72
gth646f	0:b6451e68016a	73	while (1) {
gth646f	0:b6451e68016a	74	//Prepare for burst mode on all ADC pins and set up interrupt handler (using ADC library from Simon Blandford
gth646f	0:b6451e68016a	75	adc.append(sample_ADC);
gth646f	0:b6451e68016a	76	adc.startmode(0,0);
gth646f	0:b6451e68016a	77	adc.burst(1);
gth646f	0:b6451e68016a	78	adc.setup(p20,1);
gth646f	0:b6451e68016a	79	//introduce a delay as initial waveform has bias whilst decoupling cap charges
gth646f	0:b6451e68016a	80	wait(.4);
gth646f	0:b6451e68016a	81	//start the interrupt and wait for about 4096 samples
gth646f	0:b6451e68016a	82	adc.interrupt_state(p20,1);
gth646f	0:b6451e68016a	83	wait(0.1);
gth646f	0:b6451e68016a	84	//Finsh up - Unset pin 20
gth646f	0:b6451e68016a	85	adc.interrupt_state(p20,0);
gth646f	0:b6451e68016a	86	adc.setup(p20,0);
gth646f	0:b6451e68016a	87	int actual_rate = adc.actual_sample_rate();
gth646f	0:b6451e68016a	88
gth646f	0:b6451e68016a	89	//now lets try mellen fft
gth646f	0:b6451e68016a	90	lcd.background(0x0000FF);
gth646f	0:b6451e68016a	91
gth646f	0:b6451e68016a	92	short mx[MN*2]; // input data 16 bit, 4 byte aligned x0r,x0i,x1r,x1i,....
gth646f	0:b6451e68016a	93	short my[MN*2]; // output data 16 bit,4 byte aligned y0r,y0i,y1r,y1i,....
gth646f	0:b6451e68016a	94	float data2[512];
gth646f	0:b6451e68016a	95	for (int i=0;i<MN*2;i++) mx[i]=0;
gth646f	0:b6451e68016a	96
gth646f	0:b6451e68016a	97	for (int i=0;i<MN;i=i+1) {
gth646f	0:b6451e68016a	98	mx[i*2]=Buffer[i];
gth646f	0:b6451e68016a	99	}
gth646f	0:b6451e68016a	100	//FILE* mlog = fopen("/local/mellen.csv","w");
gth646f	0:b6451e68016a	101	//call functions;
gth646f	0:b6451e68016a	102	fftR4(my, mx, MN);
gth646f	0:b6451e68016a	103	for (int i=0; i<MN; i=i+2) {
gth646f	0:b6451e68016a	104	data2[i]= sqrt(float( (my[i]my[i]) +(my[i+1]my[i+1])));
gth646f	0:b6451e68016a	105	//fprintf(mlog, "%d,%f\n", int(actual_rate/MN/2i),sqrt(float( (my[i]my[i]) +(my[i+1]*my[i+1])) ) );
gth646f	0:b6451e68016a	106	}
gth646f	0:b6451e68016a	107	//fclose(mlog);
gth646f	0:b6451e68016a	108
gth646f	0:b6451e68016a	109
gth646f	0:b6451e68016a	110	//Display amplitude on Nokia LCD
gth646f	0:b6451e68016a	111	lcd.cls();
gth646f	0:b6451e68016a	112	for (int i=0; i<128; i++) {
gth646f	0:b6451e68016a	113	data2[i+1] = 20*log10(data2[i+1]);
gth646f	0:b6451e68016a	114	lcd.fill(i, 0, 2, data2[i+1], 0x00FF00);
gth646f	0:b6451e68016a	115	}
gth646f	0:b6451e68016a	116	Counter = 0;
gth646f	0:b6451e68016a	117	}
gth646f	0:b6451e68016a	118	}
gth646f	0:b6451e68016a	119
gth646f	0:b6451e68016a	120
gth646f	0:b6451e68016a	121
gth646f	0:b6451e68016a	122
gth646f	0:b6451e68016a	123

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Type:	Program
Mbed OS support:	Mbed 2 deprecated
Created:	28 Feb 2011
Imports:	245
Forks:	0
Commits:	1
Dependents:	0
Dependencies:	2
Followers:	9

main.cpp@0:b6451e68016a, 2011-02-28 (annotated)

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