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Made a first, hacky, attempt at audio.

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This commit is contained in:
Thomas Harte 2017-03-20 19:35:51 -04:00
parent 4722f6b5c4
commit f3f4e1a541
1 changed files with 23 additions and 3 deletions
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26
Machines/Atari2600/Cartridges/CartridgePitfall2.hpp
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@ -17,11 +17,13 @@ class CartridgePitfall2: public Cartridge<CartridgePitfall2> {
Cartridge(rom),
random_number_generator_(0),
featcher_address_{0, 0, 0, 0, 0, 0, 0, 0},
mask_{0, 0, 0, 0, 0, 0, 0, 0} {
mask_{0, 0, 0, 0, 0, 0, 0, 0},
cycles_since_audio_update_(0) {
rom_ptr_ = rom_.data();
}
void perform_bus_operation(CPU6502::BusOperation operation, uint16_t address, uint8_t *value) {
cycles_since_audio_update_++;
address &= 0x1fff;
if(!(address & 0x1000)) return;
@ -43,9 +45,9 @@ class CartridgePitfall2: public Cartridge<CartridgePitfall2> {
) & 1));
break;
// Music fetcher
case 0x1005: case 0x1006: case 0x1007:
*value = 0x00;
*value = update_audio();
printf("%01x ", *value);
break;
case 0x1008: case 0x1009: case 0x100a: case 0x100b: case 0x100c: case 0x100d: case 0x100e: case 0x100f:
@ -99,11 +101,29 @@ class CartridgePitfall2: public Cartridge<CartridgePitfall2> {
return fetch_address;
}
inline uint8_t update_audio() {
unsigned int cycles_to_run_for = cycles_since_audio_update_ / 57;
cycles_since_audio_update_ %= 57;
int table_position = 0;
for(int c = 0; c < 3; c++) {
audio_channel_[c] = (audio_channel_[c] + cycles_to_run_for) % (top_[5 + c] ^ 0xff);
if((featcher_address_[5 + c] & 0x1000) && ((audio_channel_[c] ^ 0xff) > bottom_[5 + c])) {
table_position |= 0x4 >> c;
}
}
static uint8_t level_table[8] = { 0x0, 0x4, 0x5, 0x9, 0x6, 0xa, 0xb, 0xf };
return level_table[table_position];
}
uint16_t featcher_address_[8];
uint8_t top_[8], bottom_[8], mask_[8];
uint8_t music_mode_[3];
uint8_t random_number_generator_;
uint8_t *rom_ptr_;
uint8_t audio_channel_[3];
unsigned int cycles_since_audio_update_;
};
}