Shamusworld >> Repos - virtualjaguar/blob - src/dac.cpp

   1 //
   2 // DAC (really, Synchronous Serial Interface) Handler
   3 //
   4 // Originally by David Raingeard
   5 // GCC/SDL port by Niels Wagenaar (Linux/WIN32) and Caz (BeOS)
   6 // Rewritten by James L. Hammons
   7 //
   8
   9 #include "SDL.h"
  10 #include "m68k.h"
  11 #include "jaguar.h"
  12 #include "settings.h"
  13 #include "dac.h"
  14
  15 //#define DEBUG_DAC
  16
  17 #define BUFFER_SIZE             0x10000                                         // Make the DAC buffers 64K x 16 bits
  18
  19 // Jaguar memory locations
  20
  21 #define LTXD                    0xF1A148
  22 #define RTXD                    0xF1A14C
  23 #define LRXD                    0xF1A148
  24 #define RRXD                    0xF1A14C
  25 #define SCLK                    0xF1A150
  26 #define SMODE                   0xF1A154
  27
  28 // Global variables
  29
  30 uint16 lrxd, rrxd;                                                                      // I2S ports (into Jaguar)
  31
  32 // Local variables
  33
  34 uint32 LeftFIFOHeadPtr, LeftFIFOTailPtr, RightFIFOHeadPtr, RightFIFOTailPtr;
  35 SDL_AudioSpec desired;
  36
  37 // We can get away with using native endian here because we can tell SDL to use the native
  38 // endian when looking at the sample buffer, i.e., no need to worry about it.
  39
  40 uint16 * DACBuffer;
  41 uint8 SCLKFrequencyDivider = 19;                                                // Default is roughly 22 KHz (20774 Hz in NTSC mode)
  42 uint16 serialMode = 0;
  43
  44 // Private function prototypes
  45
  46 void SDLSoundCallback(void * userdata, Uint8 * buffer, int length);
  47 int GetCalculatedFrequency(void);
  48
  49 //
  50 // Initialize the SDL sound system
  51 //
  52 void DACInit(void)
  53 {
  54         memory_malloc_secure((void **)&DACBuffer, BUFFER_SIZE * sizeof(uint16), "DAC buffer");
  55
  56         desired.freq = GetCalculatedFrequency();                // SDL will do conversion on the fly, if it can't get the exact rate. Nice!
  57         desired.format = AUDIO_S16SYS;                                  // This uses the native endian (for portability)...
  58         desired.channels = 2;
  59 //      desired.samples = 4096;                                                 // Let's try a 4K buffer (can always go lower)
  60         desired.samples = 2048;                                                 // Let's try a 2K buffer (can always go lower)
  61         desired.callback = SDLSoundCallback;
  62
  63         if (SDL_OpenAudio(&desired, NULL) < 0)                  // NULL means SDL guarantees what we want
  64         {
  65                 WriteLog("DAC: Failed to initialize SDL sound. Shutting down!\n");
  66                 log_done();
  67                 exit(1);
  68         }
  69
  70         DACReset();
  71         SDL_PauseAudio(false);                                                  // Start playback!
  72         WriteLog("DAC: Successfully initialized.\n");
  73 }
  74
  75 //
  76 // Reset the sound buffer FIFOs
  77 //
  78 void DACReset(void)
  79 {
  80         LeftFIFOHeadPtr = LeftFIFOTailPtr = 0, RightFIFOHeadPtr = RightFIFOTailPtr = 1;
  81 }
  82
  83 //
  84 // Close down the SDL sound subsystem
  85 //
  86 void DACDone(void)
  87 {
  88         SDL_PauseAudio(true);
  89         SDL_CloseAudio();
  90         memory_free(DACBuffer);
  91         WriteLog("DAC: Done.\n");
  92 }
  93
  94 //
  95 // SDL callback routine to fill audio buffer
  96 //
  97 // Note: The samples are packed in the buffer in 16 bit left/16 bit right pairs.
  98 //
  99 void SDLSoundCallback(void * userdata, Uint8 * buffer, int length)
 100 {
 101         // Clear the buffer to silence, in case the DAC buffer is empty (or short)
 102         memset(buffer, desired.silence, length);
 103 //WriteLog("DAC: Inside callback...\n");
 104         if (LeftFIFOHeadPtr != LeftFIFOTailPtr)
 105         {
 106 //WriteLog("DAC: About to write some data!\n");
 107                 int numLeftSamplesReady
 108                         = (LeftFIFOTailPtr + (LeftFIFOTailPtr < LeftFIFOHeadPtr ? BUFFER_SIZE : 0))
 109                                 - LeftFIFOHeadPtr;
 110                 int numRightSamplesReady
 111                         = (RightFIFOTailPtr + (RightFIFOTailPtr < RightFIFOHeadPtr ? BUFFER_SIZE : 0))
 112                                 - RightFIFOHeadPtr;
 113                 int numSamplesReady
 114                         = (numLeftSamplesReady < numRightSamplesReady
 115                                 ? numLeftSamplesReady : numRightSamplesReady);//Hmm. * 2;
 116
 117 //The numbers look good--it's just that the DSP can't get enough samples in the DAC buffer!
 118 //WriteLog("DAC: Left/RightFIFOHeadPtr: %u/%u, Left/RightFIFOTailPtr: %u/%u\n", LeftFIFOHeadPtr, RightFIFOHeadPtr, LeftFIFOTailPtr, RightFIFOTailPtr);
 119 //WriteLog("     numLeft/RightSamplesReady: %i/%i, numSamplesReady: %i, length of buffer: %i\n", numLeftSamplesReady, numRightSamplesReady, numSamplesReady, length);
 120
 121 /*              if (numSamplesReady > length)
 122                         numSamplesReady = length;//*/
 123                 if (numSamplesReady > length / 2)       // length / 2 because we're comparing 16-bit lengths
 124                         numSamplesReady = length / 2;
 125 //else
 126 //      WriteLog("     Not enough samples to fill the buffer (short by %u L/R samples)...\n", (length / 2) - numSamplesReady);
 127 //WriteLog("DAC: %u samples ready.\n", numSamplesReady);
 128
 129                 // Actually, it's a bit more involved than this, but this is the general idea:
 130 //              memcpy(buffer, DACBuffer, length);
 131                 for(int i=0; i<numSamplesReady; i++)
 132                         ((uint16 *)buffer)[i] = DACBuffer[(LeftFIFOHeadPtr + i) % BUFFER_SIZE];
 133                         // Could also use (as long as BUFFER_SIZE is a multiple of 2):
 134 //                      buffer[i] = DACBuffer[(LeftFIFOHeadPtr + i) & (BUFFER_SIZE - 1)];
 135
 136                 LeftFIFOHeadPtr = (LeftFIFOHeadPtr + numSamplesReady) % BUFFER_SIZE;
 137                 RightFIFOHeadPtr = (RightFIFOHeadPtr + numSamplesReady) % BUFFER_SIZE;
 138                 // Could also use (as long as BUFFER_SIZE is a multiple of 2):
 139 //              LeftFIFOHeadPtr = (LeftFIFOHeadPtr + numSamplesReady) & (BUFFER_SIZE - 1);
 140 //              RightFIFOHeadPtr = (RightFIFOHeadPtr + numSamplesReady) & (BUFFER_SIZE - 1);
 141 //WriteLog("  -> Left/RightFIFOHeadPtr: %u/%u, Left/RightFIFOTailPtr: %u/%u\n", LeftFIFOHeadPtr, RightFIFOHeadPtr, LeftFIFOTailPtr, RightFIFOTailPtr);
 142         }
 143 //Hmm. Seems that the SDL buffer isn't being starved by the DAC buffer...
 144 //      else
 145 //              WriteLog("DAC: Silence...!\n");
 146 }
 147
 148 //
 149 // Calculate the frequency of SCLK * 32 using the divider
 150 //
 151 int GetCalculatedFrequency(void)
 152 {
 153         int systemClockFrequency = (vjs.hardwareTypeNTSC ? RISC_CLOCK_RATE_NTSC : RISC_CLOCK_RATE_PAL);
 154
 155         // We divide by 32 here in order to find the frequency of 32 SCLKs in a row (transferring
 156         // 16 bits of left data + 16 bits of right data = 32 bits, 1 SCLK = 1 bit transferred).
 157         return systemClockFrequency / (32 * (2 * (SCLKFrequencyDivider + 1)));
 158 }
 159
 160 //
 161 // LTXD/RTXD/SCLK/SMODE ($F1A148/4C/50/54)
 162 //
 163 void DACWriteByte(uint32 offset, uint8 data, uint32 who/*= UNKNOWN*/)
 164 {
 165         WriteLog("DAC: %s writing BYTE %02X at %08X\n", whoName[who], data, offset);
 166         if (offset == SCLK + 3)
 167                 DACWriteWord(offset - 3, (uint16)data);
 168 }
 169
 170 void DACWriteWord(uint32 offset, uint16 data, uint32 who/*= UNKNOWN*/)
 171 {
 172         if (offset == LTXD + 2)
 173         {
 174                 // Spin until buffer has been drained (for too fast processors!)...
 175 //Small problem--if Head == 0 and Tail == buffer end, then this will fail... !!! FIX !!!
 176 //[DONE]
 177                 // Also, we're taking advantage of the fact that the buffer is a multiple of two
 178                 // in this check...
 179                 while ((LeftFIFOTailPtr + 2) & (BUFFER_SIZE - 1) == LeftFIFOHeadPtr);
 180
 181                 SDL_LockAudio();                                                        // Is it necessary to do this? Mebbe.
 182                 // We use a circular buffer 'cause it's easy. Note that the callback function
 183                 // takes care of dumping audio to the soundcard...! Also note that we're writing
 184                 // the samples in the buffer in an interleaved L/R format.
 185                 LeftFIFOTailPtr = (LeftFIFOTailPtr + 2) % BUFFER_SIZE;
 186                 DACBuffer[LeftFIFOTailPtr] = data;
 187                 SDL_UnlockAudio();
 188         }
 189         else if (offset == RTXD + 2)
 190         {
 191                 // Spin until buffer has been drained (for too fast processors!)...
 192 //uint32 spin = 0;
 193                 while ((RightFIFOTailPtr + 2) & (BUFFER_SIZE - 1) == RightFIFOHeadPtr);
 194 /*              {
 195 spin++;
 196 if (spin == 0x10000000)
 197 {
 198         WriteLog("\nStuck in right DAC spinlock! Tail=%u, Head=%u\nAborting!\n", RightFIFOTailPtr, RightFIFOHeadPtr);
 199         log_done();
 200         exit(0);
 201 }
 202                 }*/
 203
 204 //This is wrong         if (RightFIFOTailPtr + 2 != RightFIFOHeadPtr)
 205 //              {
 206                 SDL_LockAudio();
 207                 RightFIFOTailPtr = (RightFIFOTailPtr + 2) % BUFFER_SIZE;
 208                 DACBuffer[RightFIFOTailPtr] = data;
 209                 SDL_UnlockAudio();
 210 //              }
 211 /*#ifdef DEBUG_DAC
 212                 else
 213                         WriteLog("DAC: Ran into FIFO's right tail pointer!\n");
 214 #endif*/
 215         }
 216         else if (offset == SCLK + 2)                                    // Sample rate
 217         {
 218                 WriteLog("DAC: Writing %u to SCLK...\n", data);
 219                 if ((uint8)data != SCLKFrequencyDivider)
 220                 {
 221                         SCLKFrequencyDivider = (uint8)data;
 222 //Of course a better way would be to query the hardware to find the upper limit...
 223                         if (data > 7)   // Anything less than 8 is too high!
 224                         {
 225                                 SDL_CloseAudio();
 226                                 desired.freq = GetCalculatedFrequency();// SDL will do conversion on the fly, if it can't get the exact rate. Nice!
 227                                 WriteLog("DAC: Changing sample rate to %u Hz!\n", desired.freq);
 228
 229                                 if (SDL_OpenAudio(&desired, NULL) < 0)  // NULL means SDL guarantees what we want
 230                                 {
 231                                         WriteLog("DAC: Failed to initialize SDL sound: %s.\nDesired freq: %u\nShutting down!\n", SDL_GetError(), desired.freq);
 232                                         log_done();
 233                                         exit(1);
 234                                 }
 235
 236                                 DACReset();
 237                                 SDL_PauseAudio(false);                          // Start playback!
 238                         }
 239                 }
 240         }
 241         else if (offset == SMODE + 2)
 242         {
 243                 serialMode = data;
 244                 WriteLog("DAC: %s writing to SMODE. Bits: %s%s%s%s%s%s [68K PC=%08X]\n", whoName[who],
 245                         (data & 0x01 ? "INTERNAL " : ""), (data & 0x02 ? "MODE " : ""),
 246                         (data & 0x04 ? "WSEN " : ""), (data & 0x08 ? "RISING " : ""),
 247                         (data & 0x10 ? "FALLING " : ""), (data & 0x20 ? "EVERYWORD" : ""),
 248                         m68k_get_reg(NULL, M68K_REG_PC));
 249         }
 250 }
 251
 252 //
 253 // LRXD/RRXD/SSTAT ($F1A148/4C/50)
 254 //
 255 uint8 DACReadByte(uint32 offset, uint32 who/*= UNKNOWN*/)
 256 {
 257 //      WriteLog("DAC: %s reading byte from %08X\n", whoName[who], offset);
 258         return 0xFF;
 259 }
 260
 261 //static uint16 fakeWord = 0;
 262 uint16 DACReadWord(uint32 offset, uint32 who/*= UNKNOWN*/)
 263 {
 264 //      WriteLog("DAC: %s reading word from %08X\n", whoName[who], offset);
 265 //      return 0xFFFF;
 266 //      WriteLog("DAC: %s reading WORD %04X from %08X\n", whoName[who], fakeWord, offset);
 267 //      return fakeWord++;
 268 //NOTE: This only works if a bunch of things are set in BUTCH which we currently don't
 269 //      check for. !!! FIX !!!
 270 // Partially fixed: We check for I2SCNTRL in the JERRY I2S routine...
 271 //      return GetWordFromButchSSI(offset, who);
 272         if (offset == LRXD || offset == RRXD)
 273                 return 0x0000;
 274         else if (offset == LRXD + 2)
 275                 return lrxd;
 276         else if (offset == RRXD + 2)
 277                 return rrxd;
 278
 279         return 0xFFFF;  // May need SSTAT as well... (but may be a Jaguar II only feature)
 280 }