mirror of
https://github.com/AppleWin/AppleWin.git
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94 lines
3.2 KiB
C++
94 lines
3.2 KiB
C++
/*
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AppleWin : An Apple //e emulator for Windows
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Copyright (C) 1994-1996, Michael O'Brien
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Copyright (C) 1999-2001, Oliver Schmidt
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Copyright (C) 2002-2005, Tom Charlesworth
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Copyright (C) 2006-2007, Tom Charlesworth, Michael Pohoreski
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AppleWin is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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AppleWin is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with AppleWin; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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/*
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SAM.CPP
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Emulate an 8 bit DAC (eg: SAM card) which writes unsigned byte
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data written to its IO area to the audio buffer (as used by the speaker).
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This merges the data with the speaker stream, reducing the volume
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of the Apple speaker when active.
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Riccardo Macri Mar 2015
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*/
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#include "StdAfx.h"
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#include "Applewin.h"
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#include "Memory.h"
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#include "SAM.h"
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#include "Speaker.h"
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//
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// Write 8 bit data to speaker. Emulates a "SAM" speech card DAC
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//
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static BYTE __stdcall IOWrite_SAM(WORD pc, WORD addr, BYTE bWrite, BYTE d, ULONG nExecutedCycles)
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{
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// Emulate audio from a SAM / 8 bit DAC card
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// Only supportable if AppleWin is using WAVE output
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//
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// This works by using the existing speaker handling but then
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// replacing the speaker audio with the 8 bit samples from the DAC
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// before they get sent out to the soundcard buffer, whilst
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// audio samples are being written to the SAM.
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//
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// Whilst very unusual, it is possible to intermingle use of SAM and the apple
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// speaker. This is crudely supported with g_bQuieterSpeaker making the Apple
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// speaker produce quieter clicks which will be crudely intermingled
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// with the SAM data. The mute gets reset after the speaker code detects
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// silence.
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if (soundtype != SOUND_WAVE)
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return MemReadFloatingBus(nExecutedCycles);
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// use existing speaker code to bring timing up to date
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BYTE res = SpkrToggle(pc, addr, bWrite, d, nExecutedCycles);
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// The DAC in the SAM uses unsigned 8 bit samples
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// The WAV data that g_nSpeakerData is loaded into is a signed short
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//
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// We convert unsigned 8 bit to signed by toggling the most significant bit
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//
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// SAM card WAV driver SAM WAV
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// 0xFF 255 0x7f 127 _ FF 7F
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// 0x81 129 0x01 1 / \
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// 0x80 128 0x00 0 / \ /80 00
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// 0x7f 127 0xFF -1 \_/
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// 0x00 0 0x80 -128 00 80
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//
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// SAM is 8 bit, PC WAV is 16 so shift audio to the MSB (<< 8)
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g_nSpeakerData = (d ^ 0x80) << 8;
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// make speaker quieter so eg: a metronome click through the
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// Apple speaker is softer vs. the analogue SAM output.
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g_bQuieterSpeaker = true;
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return res;
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}
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void ConfigureSAM(LPBYTE pCxRomPeripheral, UINT uSlot)
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{
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RegisterIoHandler(uSlot, IO_Null, IOWrite_SAM, IO_Null, IO_Null, NULL, NULL);
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}
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