Gonna bit bang this without interrupts yo

avr/send.c

@@ -6,34 +6,18 @@
 #include <tabby/printer.h>
 #include <tabby/avr/uart.h>
 
-#define TIMER1_INTERVAL 1953
+static tabby_printer_packet header = {
-
-enum {
-    TABBY_SEND_READING  =  0,
-    TABBY_SEND_BUFFERED = (1 << 0),
-    TABBY_SEND_COMPLETE = (1 << 1)
-};
-
-static volatile uint8_t bits      = 0;
-static volatile uint8_t value_in  = 0x00; /* Data coming in from Game Boy */
-static volatile uint8_t value_out = 0x00; /* Data going out to Game Boy */
-
-static volatile tabby_printer_packet header = {
     .type        = 0,
     .compression = 0,
     .size        = 0
 };
 
-static volatile uint8_t body[TABBY_PRINTER_MAX_PACKET_SIZE];
+static uint8_t body[TABBY_PRINTER_MAX_PACKET_SIZE];
 
-static volatile uint16_t sum = 0x0000;
+static uint16_t sum = 0x0000;
 
-static volatile uint8_t device = 0x00,
+static uint8_t device = 0x00,
-                        status = 0x00,
+               status = 0x00;
-                        flags  = TABBY_SEND_READING;
-
-static volatile uint16_t i = 0,
-                         b = 0;
 
 /*
  * So like, we're abusing pins here.  So badly, it's beyond.  So here's what's
@@ -45,111 +29,70 @@ static volatile uint16_t i = 0,
  * The SI and SO pins over a link cable are crossed over, so SI on one end
  * always connects to SO on the other, and vice-versa.
  */
-static void spi_start() {
+static void spi_init() {
     /*
-     * Configure MISO as output...Oddly
+     * Configure MISO as output...Oddly, alongside SCK as an output
      */
-    DDRB |=  (1 << DDB4);
+    DDRB |= ((1 << DDB5) | (1 << DDB4));
 
     /*
      * Configure MOSI as input...Also oddly
      */
     DDRB &= ~(1 << DDB3);
 
-    /*
-     * Configure SCK pin as output
-     */
-    DDRB |= (1 << DDB5);
-
     /*
      * Set output pins clear by default
      */
-    PORTB &= ~((1 << PORTB5) | (1 << PORTB4));
+    PORTB &= ~(1 << PORTB4);
-
-    /*
-     * Set timer clock divider to 1/1
-     */
-    TCCR1B = (1 << CS10);
-
-    /*
-     * Set timer interval
-     */
-    OCR1A = TIMER1_INTERVAL;
-
-    /*
-     * Reset timer counter to zero
-     */
-    TCNT1 = 0;
-
-    /*
-     * Enable timer interrupt vector for match on OCR1A
-     */
-    TIMSK1 = (1 << OCIE1A);
 }
 
-static void spi_end() {
+static uint8_t spi_send_byte(uint8_t value) {
-    PORTB  &= ~((1 << PORTB5) | (1 << PORTB4));
+    uint8_t ret = 0,
-    DDRB   &= ~((1 << DDB5)   | (1 << DDB4) | (1 << DDB3));
+              i = 0;
-    TIMSK1 &= ~ (1 << OCIE1A);
-    TCNT1   =   0;
-    OCR1A   = TIMER1_INTERVAL;
-    TCCR1B  =  (1 << CS10);
-}
 
-ISR(TIMER1_COMPA_vect) {
+    for (i=0; i<8; i++) {
-    value_in >>= 1;
+        if (value & 0x80) {
-
-    PORTB |= (1 << PORTB5);
-
-    if (PINB & (1 << PINB3)) {
-        value_in |= 0x80;
-    }
-
-    if (value_out & 0x80) {
             PORTB |=  (1 << PORTB4);
         } else {
             PORTB &= ~(1 << PORTB4);
         }
 
-    value_out <<= 1;
+        value <<= 1;
 
-    if (--bits == 0) {
+        PORTB |= (1 << PORTB5);
-        if (i < sizeof(header)) {
-            value_out = header.data[i++];
-        } else if (b < header.size) {
-            value_out = body[b++];
-        } else if (b == header.size) {
-            value_out = sum & 0x00ff;
-            b++;
-        } else if (b == header.size + 1) {
-            value_out = (sum & 0xff00) >> 8;
-            b++;
-        } else if (b == header.size + 2) {
-            device    = value_in;
-            value_out = 0x00;
-            b++;
-        } else if (b == header.size + 3) {
-            status    = value_in;
-            value_out = 0x00;
 
-            i      = 0;
-            b      = 0;
-            flags &= ~TABBY_SEND_BUFFERED;
-            flags |=  TABBY_SEND_COMPLETE;
-
-            spi_end();
-        }
-
-        bits = 8;
-    }
-
-    /*
-     * Chill out for 60µsec, then ride out the rest of the time until the next
-     * interrupt with a high as fuck SCK
-     */
         _delay_us(60);
 
+        ret <<= 1;
+
         PORTB &= ~(1 << PORTB5);
+
+        if (PINB & (1 << PINB3)) {
+            ret |= 1;
+        }
+
+        _delay_us(60);
+    }
+
+    return ret;
+}
+
+static void spi_send_packet() {
+    int i;
+
+    for (i=0; i<sizeof(header); i++) {
+        (void)spi_send_byte(header.data[i]);
+    }
+
+    for (i=0; i<header.size; i++) {
+        (void)spi_send_byte(body[i]);
+    }
+
+    (void)spi_send_byte( sum & 0x00ff);
+    (void)spi_send_byte((sum & 0xff00) >> 8);
+
+    status = spi_send_byte(0);
+    status = spi_send_byte(0);
 }
 
 static uint16_t checksum() {
@@ -169,32 +112,16 @@ static uint16_t checksum() {
 
 int main() {
     uint16_t sum = 0,
+             i = 0,
+             b = 0,
              c;
 
     uart_init();
+     spi_init();
 
     sei();
 
     while (1) {
-        uart_putchar('O', NULL);
-
-        c = uart_getchar(NULL);
-
-        if (c == 'K') {
-            break;
-        }
-    }
-
-    while (1) {
-        if (flags & TABBY_SEND_COMPLETE) {
-            uart_putchar(device, NULL);
-            uart_putchar(status, NULL);
-
-            flags = TABBY_SEND_READING;
-        }
-
-        while (flags != TABBY_SEND_READING);
-
         c = uart_getchar(NULL);
 
         switch (i) {
@@ -266,7 +193,7 @@ int main() {
 
             default: {
                 if (b < header.size) {
-                    body[b++];
+                    body[b++] = c;
                 } else if (b == header.size) {
                     sum = c;
                     b++;
@@ -277,9 +204,10 @@ int main() {
                     b = 0;
 
                     if (sum == checksum()) {
-                        flags |= TABBY_SEND_BUFFERED;
+                        spi_send_packet();
 
-                        spi_start();
+                        uart_putchar(device, NULL);
+                        uart_putchar(status, NULL);
                     }
                 }
             }