Diff: main.cpp

Revision:

1:8fda76e11be8

Parent:

0:e4f991474a45

--- a/main.cpp	Sat Oct 21 20:53:36 2017 +0000
+++ b/main.cpp	Tue Dec 05 01:55:44 2017 +0000
@@ -1,37 +1,47 @@
 #include "mbed.h"
-AnalogOut speaker(p18);
+#include "I2S.h"
 Ticker sampletick;
 DigitalOut myled(LED1);
 //Plays Audio Clip using Array in Flash
-//
-//setup const array in flash with audio values 
+//using I2S input Class D audio amp
+//setup const array in flash with audio values
 //from free wav file conversion tool at
 //http://ccgi.cjseymour.plus.com/wavtocode/wavtocode.htm
 //see https://os.mbed.com/users/4180_1/notebook/using-flash-to-play-audio-clips/
+//tested on MAX98357A
 #include "cylonbyc.h"
-
 #define sample_freq 11025.0
-//get and set the frequency from wav conversion tool GUI
-int i=0;
+
+I2S i2s(I2S_TRANSMIT, p5, p6, p7);
+//p5(PWM value sent as serial data bit) <-> Din
+//p6(WS) <-> LRC left/right channel clock
+//p7(bit clock) <-> BCLK
 
-//interrupt routine to play next audio sample from array in flash
-void audio_sample ()
+int i = 0;
+int bufflen = 1;
+int buffer[1];
+void isr()
 {
-    speaker.write_u16(sound_data[i]);
+    buffer[0] = sound_data[i]>>1;//scale down volume a bit on amp
+    i2s.write(buffer, bufflen);//Send next PWM value to amp
     i++;
     if (i>= NUM_ELEMENTS) {
         i = 0;
         sampletick.detach();
+        i2s.stop();
         myled = 0;
     }
 }
+
 int main()
 {
+    i2s.stereomono(I2S_MONO);
+    i2s.masterslave(I2S_MASTER);
+    i2s.frequency(sample_freq);
     while(1) {
+        i2s.start();
         myled = 1;
-//use a ticker to play send next audio sample value to D/A
-        sampletick.attach(&audio_sample, 1.0 / sample_freq);
-//can do other things while audio plays with timer interrupts
-        wait(10.0);
+        sampletick.attach(&isr, 1.0/sample_freq);//turn on timer interrupt
+        wait(10);
     }
 }