Printer API, compression not supported yet

Core/gb.c

@@ -543,3 +543,12 @@ void GB_set_sample_rate(GB_gameboy_t *gb, unsigned int sample_rate)
     gb->sample_rate = sample_rate;
     gb->audio_position = 0;
 }
+
+void GB_disconnect_serial(GB_gameboy_t *gb)
+{
+    gb->serial_transfer_start_callback = NULL;
+    gb->serial_transfer_end_callback = NULL;
+    
+    /* Reset any internally-emulated device. Currently, only the printer. */
+    memset(&gb->printer, 0, sizeof(gb->printer));
+}

Core/gb.h

@@ -4,6 +4,7 @@
 #include <stdint.h>
 #include <stdio.h>
 #include <time.h>
+#include "printer.h"
 #include "apu.h"
 #include "save_struct.h"
 #include "symbol_hash.h"
@@ -264,9 +265,9 @@ typedef struct GB_gameboy_s {
         bool ime_toggle; /* ei (and di in CGB) have delayed effects.*/
         bool halt_bug;
 
-        /* Misc state*/
+        /* Misc state */
-        /* IR */
         bool infrared_input;
+        GB_printer_t printer;
     );
 
     /* DMA and HDMA */
@@ -510,4 +511,5 @@ void GB_set_serial_transfer_end_callback(GB_gameboy_t *gb, GB_serial_transfer_en
 uint8_t GB_serial_get_data(GB_gameboy_t *gb);
 void GB_serial_set_data(GB_gameboy_t *gb, uint8_t data);
 
+void GB_disconnect_serial(GB_gameboy_t *gb);
 #endif /* GB_h */

Core/printer.c

@@ -0,0 +1,179 @@
+#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 serial_start(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) {
+                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;
+            }
+            break;
+        case GB_PRINTER_COMMAND_ACTIVE:
+            gb->printer.byte_to_send = 0x81;
+            break;
+        case GB_PRINTER_COMMAND_STATUS:
+            
+            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;
+            }
+            
+            /* 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 uint8_t serial_end(GB_gameboy_t *gb)
+{
+    return gb->printer.byte_to_send;
+}
+
+void GB_connect_printer(GB_gameboy_t *gb, GB_print_image_callback_t callback)
+{
+    GB_set_serial_transfer_start_callback(gb, serial_start);
+    GB_set_serial_transfer_end_callback(gb, serial_end);
+    gb->printer.callback = callback;
+}

Core/printer.h

@@ -0,0 +1,60 @@
+#ifndef printer_h
+#define printer_h
+#include <stdint.h>
+#include <stdbool.h>
+
+#define GB_PRINTER_MAX_COMMAND_LENGTH 0x280
+#define GB_PRINTER_DATA_SIZE 0x280
+
+typedef struct GB_gameboy_s GB_gameboy_t;
+
+typedef void (*GB_print_image_callback_t)(GB_gameboy_t *gb,
+                                          uint32_t *image,
+                                          uint8_t height,
+                                          uint8_t top_margin,
+                                          uint8_t bottom_margin,
+                                          uint8_t exposure);
+
+
+typedef struct
+{
+    /* Communication state machine */
+
+    enum {
+        GB_PRINTER_COMMAND_MAGIC1,
+        GB_PRINTER_COMMAND_MAGIC2,
+        GB_PRINTER_COMMAND_ID,
+        GB_PRINTER_COMMAND_COMPRESSION,
+        GB_PRINTER_COMMAND_LENGTH_LOW,
+        GB_PRINTER_COMMAND_LENGTH_HIGH,
+        GB_PRINTER_COMMAND_DATA,
+        GB_PRINTER_COMMAND_CHECKSUM_LOW,
+        GB_PRINTER_COMMAND_CHECKSUM_HIGH,
+        GB_PRINTER_COMMAND_ACTIVE,
+        GB_PRINTER_COMMAND_STATUS,
+    } command_state : 8;
+    enum {
+        GB_PRINTER_INIT_COMMAND = 1,
+        GB_PRINTER_START_COMMAND = 2,
+        GB_PRINTER_DATA_COMMAND = 4,
+        GB_PRINTER_NOP_COMMAND = 0xF,
+    } command_id : 8;
+    bool compression;
+    uint16_t length_left;
+    uint8_t command_data[GB_PRINTER_MAX_COMMAND_LENGTH];
+    uint16_t command_length;
+    uint16_t checksum;
+    uint8_t status;
+    uint8_t byte_to_send;
+    
+    uint8_t image[160 * 200];
+    uint16_t image_offset;
+    
+    GB_print_image_callback_t callback;
+} GB_printer_t;
+
+
+typedef struct GB_gameboy_s GB_gameboy_t;
+
+void GB_connect_printer(GB_gameboy_t *gb, GB_print_image_callback_t callback);
+#endif