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#include <nds.h>
#include <stdio.h>
//the record sample rate
#define sample_rate 8000
//buffer to hold sound data for playback
u16* sound_buffer = 0;
//buffer which is written to by the arm7
u16* mic_buffer = 0;
//the length of the current data
u32 data_length = 0;
//enough hold 5 seconds of 16bit audio
u32 sound_buffer_size = sample_rate * 2 * 5;
//the mic buffer sent to the arm7 is a double buffer
//every time it is half full the arm7 signals us so we can read the
//data. I want the buffer to swap about once per frame so i chose a
//buffer size large enough to hold two frames of 16bit mic data
u32 mic_buffer_size = sample_rate * 2 / 30;
//mic stream handler
void micHandler(void* data, int length)
if(!sound_buffer || data_length > sound_buffer_size) return;
DC_InvalidateRange(data, length);
dmaCopy(data, ((u8*)sound_buffer) + data_length, length);
data_length += length;
void record(void)
data_length = 0;
soundMicRecord(mic_buffer, mic_buffer_size, MicFormat_12Bit, sample_rate, micHandler);
void play(void)
iprintf("data length: %i\n", data_length);
soundPlaySample(sound_buffer, SoundFormat_16Bit, data_length, sample_rate, 127, 64, false, 0);
int main(void)
int key;
bool recording = false;
sound_buffer = (u16*)malloc(sound_buffer_size);
mic_buffer = (u16*)malloc(mic_buffer_size);
iprintf("Press A to record / play\n");
key = keysDown();
if(key & KEY_A)
recording ? play() : record();
recording = !recording;
iprintf("%s\n", recording ? "recording" : "playing");
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