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