Most amusingly I am achieving novel results with this ATmega2560

avr/Makefile

@@ -7,7 +7,7 @@ HEADER_SUBDIR	= tabby
 CROSS		= avr-
 
 CC		= $(CROSS)gcc
-CFLAGS		= $(CGFLAGS) -Wall -Os -mmcu=atmega328p -I$(INCLUDE_PATH) \
+CFLAGS		= $(CGFLAGS) -Wall -Os -mmcu=atmega2560 -I$(INCLUDE_PATH) \
 		  -DF_CPU=$(CLOCK_SPEED) -DUSE_2X
 LDFLAGS		=
 
@@ -16,7 +16,7 @@ OBJCOPY_FLAGS	= -S
 
 AVRDUDE		= avrdude
 AVRDUDE_DEVICE	= /dev/cu.usbmodem1411
-AVRDUDE_FLAGS	= -c arduino -p atmega328p -b 115200 -D -P $(AVRDUDE_DEVICE)
+AVRDUDE_FLAGS	= -c wiring -p atmega2560 -b 115200 -D -P $(AVRDUDE_DEVICE)
 
 HEADERS_LOCAL	=
 HEADERS_BUILD	= $(HEADERS_LOCAL) \

avr/send.c

@@ -7,15 +7,6 @@
 #include <tabby/avr/uart.h>
 #include <tabby/avr.h>
 
-static tabby_printer_packet   header;
-static tabby_printer_response response;
-
-static uint8_t body[TABBY_PRINTER_PACKET_MAX_SIZE];
-
-static uint8_t sheet[TABBY_PRINTER_SHEET_SIZE];
-
-static uint16_t sum;
-
 static void spi_init() {
     SC_OUTPUT();
     SO_OUTPUT();
@@ -56,30 +47,95 @@ static uint8_t spi_send_byte(uint8_t value) {
     return ret;
 }
 
-static void spi_send_packet() {
+static uint16_t checksum(tabby_printer_packet *header, uint8_t *body) {
+    uint16_t sum = 0;
+
+    int i;
+
+    for (i=2; i<sizeof(*header); i++) {
+        sum += header->data[i];
+    }
+
+    for (i=0; i<header->size; i++) {
+        sum += body[i];
+    }
+
+    return sum;
+}
+
+static void spi_send_packet(uint8_t type, uint8_t *body, uint16_t size) {
+    tabby_printer_packet header = {
+        .preamble    = { TABBY_PRINTER_SYNC_1, TABBY_PRINTER_SYNC_2 },
+        .type        = type,
+        .compression = TABBY_PRINTER_COMPRESSION_NONE,
+        .size        = size
+    };
+
+    uint16_t sum = checksum(&header, body);
+
     int i;
 
     for (i=0; i<sizeof(header); i++) {
         (void)spi_send_byte(header.data[i]);
     }
 
-    for (i=0; i<header.size; i++) {
+    for (i=0; i<size; i++) {
         (void)spi_send_byte(body[i]);
     }
 
     (void)spi_send_byte( sum & 0x00ff);
     (void)spi_send_byte((sum & 0xff00) >> 8);
 
-    response.device = spi_send_byte(0);
+    (void)spi_send_byte(0);
-    response.status = spi_send_byte(0);
+    (void)spi_send_byte(0);
+}
+
+static void spi_send_init() {
+    spi_send_packet(TABBY_PRINTER_PACKET_INIT, NULL, 0);
+}
+
+static void spi_send_job(uint8_t sheets,
+                         uint8_t linefeeds,
+                         uint8_t palette,
+                         uint8_t density) {
+    uint8_t job[4] = {
+        sheets, linefeeds, palette, density
+    };
+
+    spi_send_packet(TABBY_PRINTER_PACKET_JOB, job, sizeof(job));
+}
+
+static void spi_send_data(uint8_t *data, uint16_t size) {
+    spi_send_packet(TABBY_PRINTER_PACKET_DATA, data, size);
+}
+
+static void spi_send_sheet(uint8_t *sheet, uint16_t size) {
+    int i;
+
+    spi_send_init();
+
+    for (i=0; i<size; i+=TABBY_PRINTER_BAND_SIZE) {
+        spi_send_data(sheet + i, TABBY_PRINTER_BAND_SIZE);
+    }
+
+    spi_send_data(NULL, 0);
+
+    spi_send_job(1, 0x13, 0x00, 0x40);
 }
 
 int main() {
-    uint16_t i = 0,
+    uint16_t i            = 0,
-             b = 0;
+             b            = 0,
+             sheet_offset = 0;
 
     uint8_t c;
 
+    tabby_printer_packet header = {
+        .size = 0
+    };
+
+    uint8_t sheet[TABBY_PRINTER_SHEET_SIZE];
+
     uart_init();
      spi_init();
 
@@ -125,8 +181,11 @@ int main() {
                 switch (c) {
                     case TABBY_PRINTER_PACKET_INIT:
                     case TABBY_PRINTER_PACKET_JOB:
+                    case TABBY_PRINTER_PACKET_CANCEL: {
+                        sheet_offset = 0;
+                    }
+
                     case TABBY_PRINTER_PACKET_DATA:
-                    case TABBY_PRINTER_PACKET_CANCEL:
                     case TABBY_PRINTER_PACKET_INQUIRY: {
                         header.type = c;
                         i++;
@@ -167,20 +226,26 @@ int main() {
 
             default: {
                 if (b < header.size) {
-                    body[b++] = c;
+                    sheet[sheet_offset++] = c;
+                    b++;
                 } else if (b == header.size) {
-                    sum = c;
                     b++;
                 } else if (b == header.size + 1) {
-                    sum |= c << 8;
-
                     i = 0;
                     b = 0;
 
-                    spi_send_packet();
+                    switch (header.type) {
+                        case TABBY_PRINTER_PACKET_DATA: {
+                            if (header.size == 0) {
+                                spi_send_sheet(sheet, sheet_offset);
 
-                    uart_putchar(response.device, NULL);
+                                sheet_offset = 0;
-                    uart_putchar(response.status, NULL);
+                            }
+                        }
+                    }
+
+                    uart_putchar(TABBY_PRINTER_DEVICE_ID, NULL);
+                    uart_putchar(0x00,                    NULL);
                 }
             }
         }

bin/main.c

@@ -63,10 +63,13 @@ int main(int argc, char **argv) {
 
     tabby_printer_link_init(fd);
 
+    printf("Link initialized\n");
+
     do {
         tabby_printer_init(fd, &response);
 
         usleep(100000);
+        printf("Got response %02x%02x\n", response.device, response.status);
     } while (response.device != TABBY_PRINTER_DEVICE_ID);
 
     tabby_printer_send_sheet(fd, tile, &response);

include/tabby/avr.h

@@ -20,9 +20,9 @@
  * SC -- Serial Clock
  */
 #define SC_DDR      DDRB
-#define SC_DDB      DDB5
+#define SC_DDB      DDB1
 #define SC_PORT     PORTB
-#define SC_PORT_PIN PORTB5
+#define SC_PORT_PIN PORTB1
 
 #define SC_INPUT() \
     (SC_DDR |= ~(1 << SC_DDB))
@@ -40,11 +40,11 @@
  * SI -- Serial In
  */
 #define SI_DDR      DDRB
-#define SI_DDB      DDB3
+#define SI_DDB      DDB2
 #define SI_PIN_REG  PINB
-#define SI_PIN      PINB3
+#define SI_PIN      PINB2
 #define SI_PORT     PORTB
-#define SI_PORT_PIN PORTB3
+#define SI_PORT_PIN PORTB2
 
 #define SI_INPUT() \
     (SI_DDR &= ~(1 << SI_DDB))
@@ -59,9 +59,9 @@
  * SO -- Serial Out
  */
 #define SO_DDR      DDRB
-#define SO_DDB      DDB4
+#define SO_DDB      DDB3
 #define SO_PORT     PORTB
-#define SO_PORT_PIN PORTB4
+#define SO_PORT_PIN PORTB3
 
 #define SO_OUTPUT() \
     (SO_DDR |= (1 << SO_DDB))
@@ -73,7 +73,7 @@
     (SO_PORT &= ~(1 << SO_PORT_PIN))
 
 #define SS_DDR DDRB
-#define SS_DDB DDB2
+#define SS_DDB DDB0
 
 #define SS_INPUT() \
     (SS_DDR &= ~(1 << SS_DDB))