Chris Taylor
Emulation of the 1970's Chip-8 machine. The emulator has 7 games that are unmodified from the original Chip-8 format.
Diff: Chip8Emulator.cpp
- Revision:
- 0:bc3f11b1b41f
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/Chip8Emulator.cpp Sun Feb 08 01:58:57 2015 +0000
@@ -0,0 +1,335 @@
+#include "Chip8Emulator.h"
+#include <string.h>
+#include "GameInput.h"
+#include "Color565.h"
+
+
+DigitalOut led1(P0_18, false);
+
+const uint8_t Chip8Emulator::_font[] =
+{
+ 0xF0,0x90,0x90,0x90,0xF0, // 0
+ 0x20,0x60,0x20,0x20,0x70, // 1
+ 0xF0,0x10,0xF0,0x80,0xF0, // 2
+ 0xF0,0x10,0xF0,0x10,0xF0, // 3
+ 0x90,0x90,0xF0,0x10,0x10, // 4
+ 0xF0,0x80,0xF0,0x10,0xF0, // 5
+ 0xF0,0x80,0xF0,0x90,0xF0, // 6
+ 0xF0,0x10,0x20,0x40,0x40, // 7
+ 0xF0,0x90,0xF0,0x90,0xF0, // 8
+ 0xF0,0x90,0xF0,0x10,0xF0, // 9
+ 0xF0,0x90,0xF0,0x90,0x90, // A
+ 0xE0,0x90,0xE0,0x90,0xE0, // B
+ 0xF0,0x80,0x80,0x80,0xF0, // C
+ 0xE0,0x90,0x90,0x90,0xE0, // D
+ 0xF0,0x80,0xF0,0x80,0xF0, // E
+ 0xF0,0x80,0xF0,0x80,0x80 // F
+};
+
+Chip8Emulator::Chip8Emulator(LCD_ST7735 &screen, const uint8_t *program, uint16_t programSize, uint8_t leftKey, uint8_t rightKey, uint8_t upKey, uint8_t downKey, uint8_t fireKey, uint8_t startKey) :
+ _bmp(64, 32),
+ _screen(screen),
+ _delay(0),
+ _sound(0),
+ _pc(0x200),
+ _sp(0),
+ _i(0),
+ _leftKey(leftKey),
+ _rightKey(rightKey),
+ _upKey(upKey),
+ _downKey(downKey),
+ _fireKey(fireKey),
+ _startKey(startKey)
+{
+ memset(_memory, 0, sizeof(_memory));
+ memset(_stack, 0, sizeof(_stack));
+ memset(_registers, 0, sizeof(_registers));
+
+ memcpy(_memory, _font, sizeof(_font));
+ memcpy(_memory + _pc, program, programSize);
+}
+
+void Chip8Emulator::run()
+{
+ _screen.clearScreen(0);
+ _bmp.clear();
+
+ Timer updateTimer;
+ updateTimer.start();
+ int lastReading = updateTimer.read_ms();
+ while(true)
+ {
+ int reading = updateTimer.read_ms();
+ if (reading - lastReading > 16)
+ {
+ if (_delay > 0) --_delay;
+ if (_sound > 0) --_sound;
+ lastReading = reading;
+ }
+ wait_us(1500);
+ if (_sound != 0) led1 != led1;
+ switch(_memory[_pc] & 0xf0)
+ {
+ case 0x00:
+ switch(_memory[_pc + 1])
+ {
+ case 0xe0:
+ _bmp.clear();
+ _screen.clearScreen();
+ break;
+
+ case 0xee:
+ _pc = _stack[--_sp];
+ break;
+ }
+ break;
+
+ case 0x10:
+ _pc = ((_memory[_pc] & 0x0f) << 8) | _memory[_pc + 1];
+ continue;
+
+ case 0x20:
+ _stack[_sp++] = _pc;
+ _pc = ((_memory[_pc] & 0x0f) << 8) | _memory[_pc + 1];
+ continue;
+
+ case 0x30:
+ if (_registers[_memory[_pc] & 0x0f] == _memory[_pc + 1])
+ {
+ _pc += 2;
+ }
+ break;
+
+ case 0x40:
+ if (_registers[_memory[_pc] & 0x0f] != _memory[_pc + 1])
+ {
+ _pc += 2;
+ }
+ break;
+
+ case 0x50:
+ if (_registers[_memory[_pc] & 0x0f] == _registers[(_memory[_pc + 1] & 0x0f) >> 4])
+ {
+ _pc += 2;
+ }
+ break;
+
+ case 0x60:
+ _registers[_memory[_pc] & 0x0f] = _memory[_pc + 1];
+ break;
+
+ case 0x70:
+ _registers[_memory[_pc] & 0x0f] += _memory[_pc + 1];
+ break;
+
+ case 0x80:
+ switch(_memory[_pc + 1] & 0x0f)
+ {
+ case 0x00: _registers[_memory[_pc] & 0x0f] = _registers[(_memory[_pc + 1] & 0xf0) >> 4]; break;
+ case 0x01: _registers[_memory[_pc] & 0x0f] |= _registers[(_memory[_pc + 1] & 0xf0) >> 4]; break;
+ case 0x02: _registers[_memory[_pc] & 0x0f] &= _registers[(_memory[_pc + 1] & 0xf0) >> 4]; break;
+ case 0x03: _registers[_memory[_pc] & 0x0f] ^= _registers[(_memory[_pc + 1] & 0xf0) >> 4]; break;
+
+ case 0x04:
+ {
+ uint8_t vx = _registers[_memory[_pc] & 0x0f];
+ uint8_t vy = _registers[(_memory[_pc + 1] & 0xf0) >> 4];
+ uint16_t result = vx + vy;
+ _registers[0x0f] = (uint8_t)(result >> 8);
+ _registers[_memory[_pc] & 0x0f] = (uint8_t)result;
+ }
+ break;
+
+ case 0x05:
+ {
+ uint8_t vx = _registers[_memory[_pc] & 0x0f];
+ uint8_t vy = _registers[(_memory[_pc + 1] & 0xf0) >> 4];
+ uint16_t result = vx - vy;
+ _registers[0x0f] = (uint8_t)(((uint8_t)(result >> 8)) + 1);
+ _registers[_memory[_pc] & 0x0f] = (uint8_t)result;
+ }
+ break;
+
+ case 0x06:
+ _registers[0x0f] = (uint8_t)(_registers[_memory[_pc] & 0x0f] & 0x01);
+ _registers[_memory[_pc] & 0x0f] >>= 1;
+ break;
+
+ case 0x07:
+ _registers[0x0f] = (uint8_t)(_registers[(_memory[_pc + 1] & 0xf0) >> 4] > _registers[_memory[_pc] & 0x0f] ? 1 : 0);
+ _registers[_memory[_pc] & 0x0f] -= _registers[(_memory[_pc + 1] & 0xf0) >> 4];
+ break;
+
+ case 0x0E:
+ _registers[0x0f] = (uint8_t)(((_registers[_memory[_pc] & 0x0f] & 0x80) != 0) ? 1 : 0);
+ _registers[_memory[_pc] & 0x0f] <<= 1;
+ break;
+
+ }
+ break;
+
+ case 0x90:
+ if (_registers[_memory[_pc] & 0x0f] != _registers[(_memory[_pc + 1] & 0xf0) >> 4])
+ {
+ _pc += 2;
+ }
+ break;
+
+ case 0xA0:
+ _i = (uint16_t)(((_memory[_pc] & 0x0f) << 8) | _memory[_pc + 1]);
+ break;
+
+ case 0xB0:
+ _pc = (uint16_t)((((_memory[_pc] & 0x0f) << 8) | _memory[_pc + 1]) + _registers[0]);
+ continue;
+
+ case 0xC0:
+ _registers[_memory[_pc] & 0x0f] = (uint8_t)(rnd() & _memory[_pc + 1]);
+ break;
+
+ case 0xD0:
+ {
+ _registers[0x0f] = 0;
+ uint8_t x = _registers[_memory[_pc] & 0x0f];
+ uint8_t y = _registers[_memory[_pc + 1] >> 4];
+ uint8_t n = _memory[_pc + 1] & 0x0f;
+ for (int i = 0; i < n; i++)
+ {
+ plot(x, y + i, _memory[_i + i]);
+ }
+ }
+ break;
+
+ case 0xE0:
+ switch(_memory[_pc+1])
+ {
+ case 0x9E :
+ if (isKeyPressed(_registers[_memory[_pc] & 0x0f])) _pc += 2;
+ break;
+
+ case 0xA1 :
+ if (!isKeyPressed(_registers[_memory[_pc] & 0x0f])) _pc += 2;
+ break;
+ }
+ break;
+
+ case 0xF0:
+ switch (_memory[_pc + 1])
+ {
+ case 0x07:
+ _registers[_memory[_pc] & 0x0f] = _delay;
+ break;
+
+ case 0x0A:
+ {
+ uint8_t key = getKeyPressed();
+ if (key != 255)
+ {
+ _registers[_memory[_pc] & 0x0f] = key;
+ }
+ else
+ {
+ _pc -= 2;
+ }
+ }
+ break;
+
+ case 0x15:
+ _delay = _registers[_memory[_pc] & 0x0f];
+ break;
+
+ case 0x18:
+ _sound = _registers[_memory[_pc] & 0x0f];
+ break;
+
+ case 0x1e:
+ _i += _registers[_memory[_pc] & 0x0f];
+ break;
+
+ case 0x29:
+ _i = (uint8_t)(_registers[_memory[_pc] & 0x0f] * 5);
+ break;
+
+ case 0x33:
+ {
+ uint8_t r = _registers[_memory[_pc] & 0x0f];
+ _memory[_i + 2] = (uint8_t)(r % 10);
+ r /= 10;
+ _memory[_i + 1] = (uint8_t)(r % 10);
+ r /= 10;
+ _memory[_i] = (uint8_t)(r % 10);
+ }
+ break;
+
+ case 0x55:
+ {
+ uint8_t n = _memory[_pc] & 0x0f;
+ for (int r = 0; r <= n; r++)
+ {
+ _memory[_i + r] = _registers[r];
+ }
+ }
+ break;
+
+ case 0x65:
+ {
+ uint8_t n = _memory[_pc] & 0x0f;
+ for (int r = 0; r <= n; r++)
+ {
+ _registers[r] = _memory[_i + r];
+ }
+ }
+ break;
+ }
+ break;
+ }
+
+ _pc += 2;
+ if (_pc >= sizeof(_memory))
+ {
+ _pc = 0x200 + (sizeof(_memory) - _pc - 1);
+ }
+ }
+}
+
+uint8_t Chip8Emulator::rnd()
+{
+ return (uint8_t)(rand() % 256);
+}
+
+bool Chip8Emulator::isKeyPressed(uint8_t key)
+{
+ return getKeyPressed() == key;
+}
+
+uint8_t Chip8Emulator::getKeyPressed()
+{
+ if (GameInput::isLeftPressed()) return _leftKey;
+ if (GameInput::isRightPressed()) return _rightKey;
+ if (GameInput::isUpPressed()) return _upKey;
+ if (GameInput::isDownPressed()) return _downKey;
+ if (GameInput::isCirclePressed()) return _fireKey;
+ if (GameInput::isSquarePressed()) return _startKey;
+
+ return 255;
+}
+
+void Chip8Emulator::plot(int x, int y, uint8_t pattern)
+{
+ if (y >= 32) return;
+ for (int i = 0; i < 8; ++i)
+ {
+ if (x + i >= 64) return;
+
+ uint16_t set = ((pattern << i) & 0x80) != 0 ? 1 : 0;
+ uint16_t current = _bmp.getPixel(x + i, y);
+
+ if ((set & current) != 0) _registers[0x0f] = 1;
+
+ _bmp.setPixel(x + i, y, current ^ set);
+
+ int nx = OFFSET_X + (x + i) * 2;
+ int ny = OFFSET_Y + (y * 2);
+ _screen.fillRect(nx, ny, nx + 1, ny + 1, current ^ set ? Color565::White : Color565::Black);
+ }
+}
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