main.cpp

00001 #include "mbed.h"
00002 //I2S Demo to display values from I2S microphone
00003 //
00004 //Only works on mbed LPC1768 - I2S is not an mbed API!
00005 //Microphone used is SPH0645LM4H
00006 //see https://www.adafruit.com/product/3421
00007 
00008 #include "I2S.h"
00009 //uses patched mbed I2S library from 
00010 //https://os.mbed.com/users/p07gbar/code/I2S/
00011 //Needed a typo patch - clock was swapped p30/p15 in pin function setup code
00012 //"if (_clk == p15)" changed to "if (_clk != p15)" in I2S.cpp line 494
00013 BusOut mylevel(LED4,LED3,LED2,LED1);
00014 //4 built in mbed LEDs display audio level
00015 
00016 #define sample_freq 32000.0
00017 
00018 //Uses I2S hardware for input
00019 I2S i2srx(I2S_RECEIVE, p17, p16, p15);
00020 //p17(PWM value sent as serial data bit) <-> Dout
00021 //p16(WS) <-> LRC left/right channel clock
00022 //p15(bit clock) <-> BCLK 
00023 
00024 volatile int i=0;
00025 
00026 void i2s_isr() //interrupt routine to read microphone
00027 {
00028     i = i2srx.read();//read value using I2S input
00029     mylevel = (i>>7)& 0xF; //Display Audio Level on 4 LEDs
00030 }
00031 int main()
00032 {
00033     i2srx.stereomono(I2S_MONO);//mono not stereo mode
00034     i2srx.masterslave(I2S_MASTER);//master drives clocks
00035     i2srx.frequency(sample_freq);//set sample freq
00036     i2srx.set_interrupt_fifo_level(1);//interrupt on one sample
00037     i2srx.attach(&i2s_isr);//set I2S ISR
00038     i2srx.start();//start I2S and interrupts
00039     while(1) {
00040         printf("%X\n\r",(i>>16)&(0x0000FFFF));
00041         wait(0.5);
00042     }
00043 }