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

   1 //
   2 // DAC (really, Synchronous Serial Interface) Handler
   3 //
   4 // Original by Cal2
   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 "SDL.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 SCLK                    0xF1A150
  24 #define SMODE                   0xF1A154
  25
  26 // Local variables
  27
  28 uint32 LeftFIFOHeadPtr, LeftFIFOTailPtr, RightFIFOHeadPtr, RightFIFOTailPtr;
  29 SDL_AudioSpec desired;
  30
  31 // We can get away with using native endian here because we can tell SDL to use the native
  32 // endian when looking at the sample buffer, i.e., no need to worry about it.
  33
  34 uint16 * DACBuffer;
  35 uint8 SCLKFrequencyDivider = 19;                                                // Default is roughly 22 KHz (20774 Hz in NTSC mode)
  36 uint16 serialMode = 0;
  37
  38 // Private function prototypes
  39
  40 void SDLSoundCallback(void * userdata, Uint8 * buffer, int length);
  41 int GetCalculatedFrequency(void);
  42
  43 //
  44 // Initialize the SDL sound system
  45 //
  46 void DACInit(void)
  47 {
  48         memory_malloc_secure((void **)&DACBuffer, BUFFER_SIZE * sizeof(uint16), "DAC buffer");
  49
  50         desired.freq = GetCalculatedFrequency();                // SDL will do conversion on the fly, if it can't get the exact rate. Nice!
  51         desired.format = AUDIO_S16SYS;                                  // This uses the native endian (for portability)...
  52         desired.channels = 2;
  53 //      desired.samples = 4096;                                                 // Let's try a 4K buffer (can always go lower)
  54         desired.samples = 2048;                                                 // Let's try a 2K buffer (can always go lower)
  55         desired.callback = SDLSoundCallback;
  56
  57         if (SDL_OpenAudio(&desired, NULL) < 0)                  // NULL means SDL guarantees what we want
  58         {
  59                 WriteLog("DAC: Failed to initialize SDL sound. Shutting down!\n");
  60                 log_done();
  61                 exit(1);
  62         }
  63
  64         DACReset();
  65         SDL_PauseAudio(false);                                                  // Start playback!
  66         WriteLog("DAC: Successfully initialized.\n");
  67 }
  68
  69 //
  70 // Reset the sound buffer FIFOs
  71 //
  72 void DACReset(void)
  73 {
  74         LeftFIFOHeadPtr = LeftFIFOTailPtr = 0, RightFIFOHeadPtr = RightFIFOTailPtr = 1;
  75 }
  76
  77 //
  78 // Close down the SDL sound subsystem
  79 //
  80 void DACDone(void)
  81 {
  82         SDL_PauseAudio(true);
  83         SDL_CloseAudio();
  84         memory_free(DACBuffer);
  85         WriteLog("DAC: Done.\n");
  86 }
  87
  88 //
  89 // SDL callback routine to fill audio buffer
  90 //
  91 // Note: The samples are packed in the buffer in 16 bit left/16 bit right pairs.
  92 //
  93 void SDLSoundCallback(void * userdata, Uint8 * buffer, int length)
  94 {
  95         // Clear the buffer to silence, in case the DAC buffer is empty (or short)
  96         memset(buffer, desired.silence, length);
  97 //WriteLog("DAC: Inside callback...\n");
  98         if (LeftFIFOHeadPtr != LeftFIFOTailPtr)
  99         {
 100 //WriteLog("DAC: About to write some data!\n");
 101                 int numLeftSamplesReady
 102                         = (LeftFIFOTailPtr + (LeftFIFOTailPtr < LeftFIFOHeadPtr ? BUFFER_SIZE : 0))
 103                                 - LeftFIFOHeadPtr;
 104                 int numRightSamplesReady
 105                         = (RightFIFOTailPtr + (RightFIFOTailPtr < RightFIFOHeadPtr ? BUFFER_SIZE : 0))
 106                                 - RightFIFOHeadPtr;
 107                 int numSamplesReady
 108                         = (numLeftSamplesReady < numRightSamplesReady
 109                                 ? numLeftSamplesReady : numRightSamplesReady);//Hmm. * 2;
 110
 111 //The numbers look good--it's just that the DSP can't get enough samples in the DAC buffer!
 112 //WriteLog("DAC: Left/RightFIFOHeadPtr: %u/%u, Left/RightFIFOTailPtr: %u/%u\n", LeftFIFOHeadPtr, RightFIFOHeadPtr, LeftFIFOTailPtr, RightFIFOTailPtr);
 113 //WriteLog("     numLeft/RightSamplesReady: %i/%i, numSamplesReady: %i, length of buffer: %i\n", numLeftSamplesReady, numRightSamplesReady, numSamplesReady, length);
 114
 115 /*              if (numSamplesReady > length)
 116                         numSamplesReady = length;//*/
 117                 if (numSamplesReady > length / 2)       // length / 2 because we're comparing 16-bit lengths
 118                         numSamplesReady = length / 2;
 119 //else
 120 //      WriteLog("     Not enough samples to fill the buffer (short by %u L/R samples)...\n", (length / 2) - numSamplesReady);
 121 //WriteLog("DAC: %u samples ready.\n", numSamplesReady);
 122
 123                 // Actually, it's a bit more involved than this, but this is the general idea:
 124 //              memcpy(buffer, DACBuffer, length);
 125                 for(int i=0; i<numSamplesReady; i++)
 126                         ((uint16 *)buffer)[i] = DACBuffer[(LeftFIFOHeadPtr + i) % BUFFER_SIZE];
 127                         // Could also use (as long as BUFFER_SIZE is a multiple of 2):
 128 //                      buffer[i] = DACBuffer[(LeftFIFOHeadPtr + i) & (BUFFER_SIZE - 1)];
 129
 130                 LeftFIFOHeadPtr = (LeftFIFOHeadPtr + numSamplesReady) % BUFFER_SIZE;
 131                 RightFIFOHeadPtr = (RightFIFOHeadPtr + numSamplesReady) % BUFFER_SIZE;
 132                 // Could also use (as long as BUFFER_SIZE is a multiple of 2):
 133 //              LeftFIFOHeadPtr = (LeftFIFOHeadPtr + numSamplesReady) & (BUFFER_SIZE - 1);
 134 //              RightFIFOHeadPtr = (RightFIFOHeadPtr + numSamplesReady) & (BUFFER_SIZE - 1);
 135 //WriteLog("  -> Left/RightFIFOHeadPtr: %u/%u, Left/RightFIFOTailPtr: %u/%u\n", LeftFIFOHeadPtr, RightFIFOHeadPtr, LeftFIFOTailPtr, RightFIFOTailPtr);
 136         }
 137 //Hmm. Seems that the SDL buffer isn't being starved by the DAC buffer...
 138 //      else
 139 //              WriteLog("DAC: Silence...!\n");
 140 }
 141
 142 //
 143 // Calculate the frequency of SCLK * 32 using the divider
 144 //
 145 int GetCalculatedFrequency(void)
 146 {
 147         int systemClockFrequency = (vjs.hardwareTypeNTSC ? RISC_CLOCK_RATE_NTSC : RISC_CLOCK_RATE_PAL);
 148
 149         // We divide by 32 here in order to find the frequency of 32 SCLKs in a row (transferring
 150         // 16 bits of left data + 16 bits of right data = 32 bits, 1 SCLK = 1 bit transferred).
 151         return systemClockFrequency / (32 * (2 * (SCLKFrequencyDivider + 1)));
 152 }
 153
 154 //
 155 // LTXD/RTXD/SCLK/SMODE ($F1A148/4C/50/54)
 156 //
 157 void DACWriteByte(uint32 offset, uint8 data)
 158 {
 159         WriteLog("DAC: Writing %02X at %08X\n", data, offset);
 160         if (offset == SCLK + 3)
 161                 DACWriteWord(offset - 3, (uint16)data);
 162 }
 163
 164 void DACWriteWord(uint32 offset, uint16 data)
 165 {
 166         if (offset == LTXD + 2)
 167         {
 168                 // Spin until buffer has been drained (for too fast processors!)...
 169 //Small problem--if Head == 0 and Tail == buffer end, then this will fail... !!! FIX !!!
 170 //[DONE]
 171                 // Also, we're taking advantage of the fact that the buffer is a multiple of two
 172                 // in this check...
 173                 while ((LeftFIFOTailPtr + 2) & (BUFFER_SIZE - 1) == LeftFIFOHeadPtr);
 174
 175                 SDL_LockAudio();                                                        // Is it necessary to do this? Mebbe.
 176                 // We use a circular buffer 'cause it's easy. Note that the callback function
 177                 // takes care of dumping audio to the soundcard...! Also note that we're writing
 178                 // the samples in the buffer in an interleaved L/R format.
 179                 LeftFIFOTailPtr = (LeftFIFOTailPtr + 2) % BUFFER_SIZE;
 180                 DACBuffer[LeftFIFOTailPtr] = data;
 181                 SDL_UnlockAudio();
 182         }
 183         else if (offset == RTXD + 2)
 184         {
 185                 // Spin until buffer has been drained (for too fast processors!)...
 186 //uint32 spin = 0;
 187                 while ((RightFIFOTailPtr + 2) & (BUFFER_SIZE - 1) == RightFIFOHeadPtr);
 188 /*              {
 189 spin++;
 190 if (spin == 0x10000000)
 191 {
 192         WriteLog("\nStuck in right DAC spinlock! Tail=%u, Head=%u\nAborting!\n", RightFIFOTailPtr, RightFIFOHeadPtr);
 193         log_done();
 194         exit(0);
 195 }
 196                 }*/
 197
 198 //This is wrong         if (RightFIFOTailPtr + 2 != RightFIFOHeadPtr)
 199 //              {
 200                 SDL_LockAudio();
 201                 RightFIFOTailPtr = (RightFIFOTailPtr + 2) % BUFFER_SIZE;
 202                 DACBuffer[RightFIFOTailPtr] = data;
 203                 SDL_UnlockAudio();
 204 //              }
 205 /*#ifdef DEBUG_DAC
 206                 else
 207                         WriteLog("DAC: Ran into FIFO's right tail pointer!\n");
 208 #endif*/
 209         }
 210         else if (offset == SCLK + 2)                                    // Sample rate
 211         {
 212                 WriteLog("DAC: Writing %u to SCLK...\n", data);
 213                 if ((uint8)data != SCLKFrequencyDivider)
 214                 {
 215                         SCLKFrequencyDivider = (uint8)data;
 216 //Of course a better way would be to query the hardware to find the upper limit...
 217                         if (data > 7)   // Anything less than 8 is too high!
 218                         {
 219                                 SDL_CloseAudio();
 220                                 desired.freq = GetCalculatedFrequency();// SDL will do conversion on the fly, if it can't get the exact rate. Nice!
 221                                 WriteLog("DAC: Changing sample rate to %u Hz!\n", desired.freq);
 222
 223                                 if (SDL_OpenAudio(&desired, NULL) < 0)  // NULL means SDL guarantees what we want
 224                                 {
 225                                         WriteLog("DAC: Failed to initialize SDL sound: %s.\nDesired freq: %u\nShutting down!\n", SDL_GetError(), desired.freq);
 226                                         log_done();
 227                                         exit(1);
 228                                 }
 229
 230                                 DACReset();
 231                                 SDL_PauseAudio(false);                          // Start playback!
 232                         }
 233                 }
 234         }
 235         else if (offset == SMODE + 2)
 236         {
 237                 serialMode = data;
 238                 WriteLog("DAC: Writing to SMODE. Bits: %s%s%s%s%s%s\n",
 239                         (data & 0x01 ? "INTERNAL " : ""), (data & 0x02 ? "MODE " : ""),
 240                         (data & 0x04 ? "WSEN " : ""), (data & 0x08 ? "RISING " : ""),
 241                         (data & 0x10 ? "FALLING " : ""), (data & 0x20 ? "EVERYWORD" : ""));
 242         }
 243 }
 244
 245 //
 246 // LRXD/RRXD/SSTAT ($F1A148/4C/50)
 247 //
 248 uint8 DACReadByte(uint32 offset)
 249 {
 250 //      WriteLog("DAC: Reading byte from %08X\n", offset);
 251         return 0xFF;
 252 }
 253
 254 uint16 DACReadWord(uint32 offset)
 255 {
 256 //      WriteLog("DAC: Reading word from %08X\n", offset);
 257         return 0xFFFF;
 258 }