main.cpp

00001 // Hello World example for the USBAudio library
00002  
00003 #include "mbed.h"
00004 #include "USBAudio.h"
00005 PwmOut led(p22);
00006 Serial pc(USBTX, USBRX);
00007  
00008 // frequency: 48 kHz
00009 #define FREQ 48000
00010  
00011 // 1 channel: mono
00012 #define NB_CHA 1
00013  
00014 // length of an audio packet: each ms, we receive 48 * 16bits ->48 * 2 bytes. as there is one channel, the length will be 48 * 2 * 1
00015 #define AUDIO_LENGTH_PACKET FREQ/1000 * 2 * 1
00016  
00017 // USBAudio
00018 USBAudio audio(FREQ, NB_CHA);
00019 int16_t buf[AUDIO_LENGTH_PACKET/2];
00020 float bufo[2][AUDIO_LENGTH_PACKET/2];
00021 bool swb=false,swb2=false;
00022 int pli=0;
00023 void Sample_timer_interrupt(void)
00024 {
00025     //static unsigned int i=0;
00026  
00027     // send next analog sample out to D to A
00028     led = bufo[swb][pli];
00029     // increment pointer and wrap around back to 0 at 128
00030  pli++;
00031     if(pli==(AUDIO_LENGTH_PACKET>>1))pli=0,swb=!swb;
00032  //if(i==0)audio.read((uint8_t *)buf);
00033 }
00034  
00035 int main() {
00036     //int16_t buf[AUDIO_LENGTH_PACKET/2];
00037    //led.pulsewidth(0.000000001);
00038     led.period(1.0/(96000.0*2));//1.0/(48000.0*16));
00039     // set up a timer to be used for sample rate interrupts
00040     Ticker Sample_Period;
00041       Sample_Period.attach(&Sample_timer_interrupt, 1.0/(FREQ));
00042      // audio.read((uint8_t *)buf);
00043     while (1) {
00044         // read an audio packet
00045         audio.read((uint8_t *)buf);
00046         float vol=audio.getVolume();
00047         // print packet received
00048         //pc.printf("recv: ");
00049         //swb2=false;
00050         for(int i = 0; i < (AUDIO_LENGTH_PACKET>>1); i++) {
00051           bufo[!swb][i]=((float)buf[i]*vol/510.0)+0.5;}
00052           pli=0;
00053           //swb2=true;
00054           //  led = (float)buf[i]/128.0;
00055             //pc.printf("%d ", buf[i]);
00056            // led=(float)buf[i]/128.0;
00057        // }
00058        // pc.printf("\r\n");
00059     }
00060     
00061 }