Sheldon Cooper
Plays USB Audio packets through external DAC (Cirrus Logic CS4344). Simple demo code, don't expect a sophisticated I2S library. HW setup: mbed DIP 5 (I2STX_SDA) -> DAC SDIN (Serial Audio Data Input) mbed DIP 6 (I2STX_WS) -> DAC LRCK (Left Right Clock) mbed DIP 7 (I2STX_CLK) -> DAC SCLK (External Serial Clock Input) mbed DIP 30 (I2SRX_CLK) -> DAC MCLK (Master Clock) also needed an extra USB connector wired to mbed. Does not work with built-in USB. Code needs a bit of clean up.
Diff: main.cpp
- Revision:
- 0:bf9e7b99dda5
- Child:
- 1:12e8ee1b7ea2
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp Mon Apr 16 08:28:42 2012 +0000
@@ -0,0 +1,33 @@
+#include "mbed.h"
+#include "USBAudio.h"
+#include "I2S.h"
+
+Serial pc(USBTX, USBRX);
+
+// frequency: 48 kHz
+#define FREQ 48000
+
+// 1 channel: mono
+#define NB_CHA 2
+
+// length of an audio packet: each ms, we receive 48 * 16bits ->48 * 2 bytes per channel. For stereo multiply by 2
+#define AUDIO_LENGTH_PACKET 48 * 2 * 2
+
+// USBAudio
+USBAudio audio(FREQ, NB_CHA,FREQ, NB_CHA,0x7bb8, 0x1112);
+
+int main() {
+ int16_t buf[AUDIO_LENGTH_PACKET/2];
+
+
+ setup(&pc);
+ pc.printf("Begin new\n");
+
+ while (1) {
+ // read an audio packet
+ audio.read((uint8_t *)buf);
+
+ // send to DAC
+ play(buf,AUDIO_LENGTH_PACKET/2);
+ }
+}