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SameBoy/Core/printer.c

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C
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#include "gb.h"
/* TODO: Emulation is VERY basic and assumes the ROM correctly uses the printer's interface.
Incorrect usage is not correctly emulated, as it's not well documented, nor do I
have my own GB Printer to figure it out myself.
It also does not currently emulate communication timeout, which means that a bug
might prevent the printer operation until the GameBoy is restarted.
Also, field mask values are assumed. */
static void handle_command(GB_gameboy_t *gb)
{
switch (gb->printer.command_id) {
case GB_PRINTER_INIT_COMMAND:
gb->printer.status = 0;
gb->printer.image_offset = 0;
break;
case GB_PRINTER_START_COMMAND:
if (gb->printer.command_length == 4) {
gb->printer.status = 6; /* Printing */
uint32_t image[gb->printer.image_offset];
uint8_t palette = gb->printer.command_data[2];
uint32_t colors[4] = {gb->rgb_encode_callback(gb, 0xff, 0xff, 0xff),
gb->rgb_encode_callback(gb, 0xaa, 0xaa, 0xaa),
gb->rgb_encode_callback(gb, 0x55, 0x55, 0x55),
gb->rgb_encode_callback(gb, 0x00, 0x00, 0x00)};
for (unsigned i = 0; i < gb->printer.image_offset; i++) {
image[i] = colors[(palette >> (gb->printer.image[i] * 2)) & 3];
}
if (gb->printer_callback) {
gb->printer_callback(gb, image, gb->printer.image_offset / 160,
gb->printer.command_data[1] >> 4, gb->printer.command_data[1] & 7,
gb->printer.command_data[3] & 0x7F);
}
gb->printer.image_offset = 0;
}
break;
case GB_PRINTER_DATA_COMMAND:
if (gb->printer.command_length == GB_PRINTER_DATA_SIZE) {
gb->printer.image_offset %= sizeof(gb->printer.image);
gb->printer.status = 8; /* Received 0x280 bytes */
uint8_t *byte = gb->printer.command_data;
for (unsigned row = 2; row--; ) {
for (unsigned tile_x = 0; tile_x < 160 / 8; tile_x++) {
for (unsigned y = 0; y < 8; y++, byte += 2) {
for (unsigned x_pixel = 0; x_pixel < 8; x_pixel++) {
gb->printer.image[gb->printer.image_offset + tile_x * 8 + x_pixel + y * 160] =
((*byte) >> 7) | (((*(byte + 1)) >> 7) << 1);
(*byte) <<= 1;
(*(byte + 1)) <<= 1;
}
}
}
gb->printer.image_offset += 8 * 160;
}
}
case GB_PRINTER_NOP_COMMAND:
default:
break;
}
}
static void byte_recieve_completed(GB_gameboy_t *gb, uint8_t byte_received)
{
gb->printer.byte_to_send = 0;
switch (gb->printer.command_state) {
case GB_PRINTER_COMMAND_MAGIC1:
if (byte_received != 0x88) {
return;
}
gb->printer.status &= ~1;
gb->printer.command_length = 0;
gb->printer.checksum = 0;
break;
case GB_PRINTER_COMMAND_MAGIC2:
if (byte_received != 0x33) {
if (byte_received != 0x88) {
gb->printer.command_state = GB_PRINTER_COMMAND_MAGIC1;
}
return;
}
break;
case GB_PRINTER_COMMAND_ID:
gb->printer.command_id = byte_received & 0xF;
break;
case GB_PRINTER_COMMAND_COMPRESSION:
gb->printer.compression = byte_received & 1;
break;
case GB_PRINTER_COMMAND_LENGTH_LOW:
gb->printer.length_left = byte_received;
break;
case GB_PRINTER_COMMAND_LENGTH_HIGH:
gb->printer.length_left |= (byte_received & 3) << 8;
break;
case GB_PRINTER_COMMAND_DATA:
if (gb->printer.command_length != GB_PRINTER_MAX_COMMAND_LENGTH) {
if (gb->printer.compression) {
if (!gb->printer.compression_run_lenth) {
gb->printer.compression_run_is_compressed = byte_received & 0x80;
gb->printer.compression_run_lenth = (byte_received & 0x7F) + 1 + gb->printer.compression_run_is_compressed;
}
else if (gb->printer.compression_run_is_compressed) {
while (gb->printer.compression_run_lenth) {
gb->printer.command_data[gb->printer.command_length++] = byte_received;
gb->printer.compression_run_lenth--;
if (gb->printer.command_length == GB_PRINTER_MAX_COMMAND_LENGTH) {
gb->printer.compression_run_lenth = 0;
}
}
}
else {
gb->printer.command_data[gb->printer.command_length++] = byte_received;
gb->printer.compression_run_lenth--;
}
}
else {
gb->printer.command_data[gb->printer.command_length++] = byte_received;
}
}
gb->printer.length_left--;
break;
case GB_PRINTER_COMMAND_CHECKSUM_LOW:
gb->printer.checksum ^= byte_received;
break;
case GB_PRINTER_COMMAND_CHECKSUM_HIGH:
gb->printer.checksum ^= byte_received << 8;
if (gb->printer.checksum) {
gb->printer.status |= 1; /* Checksum error*/
gb->printer.command_state = GB_PRINTER_COMMAND_MAGIC1;
return;
}
gb->printer.byte_to_send = 0x81;
break;
case GB_PRINTER_COMMAND_ACTIVE:
if ((gb->printer.command_id & 0xF) == GB_PRINTER_INIT_COMMAND) {
/* Games expect INIT commands to return 0? */
gb->printer.byte_to_send = 0;
}
else {
gb->printer.byte_to_send = gb->printer.status;
}
break;
case GB_PRINTER_COMMAND_STATUS:
/* Printing is done instantly, but let the game recieve a 6 (Printing) status at least once, for compatibility */
if (gb->printer.status == 6) {
gb->printer.status = 4; /* Done */
}
gb->printer.command_state = GB_PRINTER_COMMAND_MAGIC1;
handle_command(gb);
return;
}
if (gb->printer.command_state >= GB_PRINTER_COMMAND_ID && gb->printer.command_state < GB_PRINTER_COMMAND_CHECKSUM_LOW) {
gb->printer.checksum += byte_received;
}
if (gb->printer.command_state != GB_PRINTER_COMMAND_DATA) {
gb->printer.command_state++;
}
if (gb->printer.command_state == GB_PRINTER_COMMAND_DATA) {
if (gb->printer.length_left == 0) {
gb->printer.command_state++;
}
}
}
static void serial_start(GB_gameboy_t *gb, bool bit_received)
{
if (gb->printer.idle_time > GB_get_unmultiplied_clock_rate(gb)) {
gb->printer.command_state = GB_PRINTER_COMMAND_MAGIC1;
gb->printer.bits_received = 0;
}
gb->printer.idle_time = 0;
gb->printer.byte_being_received <<= 1;
gb->printer.byte_being_received |= bit_received;
gb->printer.bits_received++;
if (gb->printer.bits_received == 8) {
byte_recieve_completed(gb, gb->printer.byte_being_received);
gb->printer.bits_received = 0;
gb->printer.byte_being_received = 0;
}
}
static bool serial_end(GB_gameboy_t *gb)
{
bool ret = gb->printer.bit_to_send;
gb->printer.bit_to_send = gb->printer.byte_to_send & 0x80;
gb->printer.byte_to_send <<= 1;
return ret;
}
void GB_connect_printer(GB_gameboy_t *gb, GB_print_image_callback_t callback)
{
memset(&gb->printer, 0, sizeof(gb->printer));
GB_set_serial_transfer_bit_start_callback(gb, serial_start);
GB_set_serial_transfer_bit_end_callback(gb, serial_end);
gb->printer_callback = callback;
}
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