Surprise! Added support for microphone emulation, but only for Win32.

There are 3 problems : 
1. the sound crackles a bit
2. the microphone amplifier isn't supported
3. the emu freezes if you don't close it by the console

desmume/src/windows/mic.cpp

@@ -0,0 +1,131 @@
+/*
+	Microphone emulation for Win32
+
+	The NDS microphone produces 8-bit sound sampled at 16khz.
+	The sound data must be read sample-by-sample through the 
+	ARM7 SPI device (touchscreen controller, channel 6).
+
+	Note : I added these notes because the microphone isn't 
+	documented on GBATek.
+*/
+#include <windows.h>
+#include "../types.h"
+#include "../debug.h"
+#include "../mic.h"
+
+#define MIC_CHECKERR(hr) if(hr != MMSYSERR_NOERROR) return FALSE;
+
+#define MIC_BUFSIZE 4096
+
+BOOL Mic_Inited = FALSE;
+
+s8 Mic_Buffer[MIC_BUFSIZE];
+u16 Mic_BufPos;
+
+HWAVEIN waveIn;
+WAVEHDR waveHdr;
+
+static int CALLBACK waveInProc(HWAVEIN wavein, UINT msg, DWORD instance, DWORD param1, DWORD param2)
+{
+	LPWAVEHDR lpWaveHdr;
+	HRESULT hr;
+
+	if(!Mic_Inited)
+		return 1;
+
+	if(msg == WIM_DATA)
+	{
+		lpWaveHdr = (LPWAVEHDR)param1;
+
+		hr = waveInAddBuffer(waveIn, lpWaveHdr, sizeof(WAVEHDR));
+		if(hr != MMSYSERR_NOERROR)
+			return 1;
+	}
+
+	return 0;
+}
+
+BOOL Mic_Init()
+{
+	if(Mic_Inited)
+		return TRUE;
+
+	Mic_Inited = FALSE;
+
+	HRESULT hr;
+	WAVEFORMATEX wfx;
+
+	memset(Mic_Buffer, 0, MIC_BUFSIZE);
+	Mic_BufPos = 0;
+
+	memset(&wfx, 0, sizeof(wfx));
+	wfx.cbSize = 0;
+	wfx.wFormatTag = WAVE_FORMAT_PCM;
+	wfx.nChannels = 1;
+	wfx.nSamplesPerSec = 16000;
+	wfx.nBlockAlign = 1;
+	wfx.nAvgBytesPerSec = 16000;
+	wfx.wBitsPerSample = 8;
+
+	hr = waveInOpen(&waveIn, WAVE_MAPPER, &wfx, (DWORD_PTR)waveInProc, 0, CALLBACK_FUNCTION);
+	MIC_CHECKERR(hr)
+
+	memset(&waveHdr, 0, sizeof(waveHdr));
+	waveHdr.lpData = (LPSTR)Mic_Buffer;
+	waveHdr.dwBufferLength = MIC_BUFSIZE;
+
+	hr = waveInPrepareHeader(waveIn, &waveHdr, sizeof(WAVEHDR));
+	MIC_CHECKERR(hr)
+
+	hr = waveInAddBuffer(waveIn, &waveHdr, sizeof(WAVEHDR));
+	MIC_CHECKERR(hr)
+
+	hr = waveInStart(waveIn);
+	MIC_CHECKERR(hr)
+
+	Mic_Inited = TRUE;
+	return TRUE;
+}
+
+void Mic_Reset()
+{
+	if(!Mic_Inited)
+		return;
+
+	memset(Mic_Buffer, 0, MIC_BUFSIZE);
+	Mic_BufPos = 0;
+}
+
+void Mic_DeInit()
+{
+	if(!Mic_Inited)
+		return;
+
+	waveInReset(waveIn);
+	waveInClose(waveIn);
+
+	Mic_Inited = FALSE;
+}
+
+u8 Mic_ReadSample()
+{
+	if(!Mic_Inited)
+		return 0;
+
+	u8 tmp = (u8)Mic_Buffer[Mic_BufPos >> 1];
+	u8 ret;
+
+	if(Mic_BufPos & 0x1)
+	{
+		ret = ((tmp & 0x1) << 7);
+	}
+	else
+	{
+		ret = ((tmp & 0xFE) >> 1);
+	}
+
+	Mic_BufPos++;
+	Mic_BufPos %= (MIC_BUFSIZE << 1);
+
+	return ret;
+}