Use pin change interrupt to react faster to the clock

diff --git a/s88w/s88w-r.c b/s88w/s88w-r.c
index 15365b43500d117d7a714b6f4cc383b8948575e6..171653299fd2568bfbe91b58aca5fc6b3dc089df 100644 (file)
--- a/s88w/s88w-r.c
+++ b/s88w/s88w-r.c
@@ -37,26 +37,27 @@ void check_input();
 uint8_t hexdigit(uint8_t);
 uint8_t decode_hex(uint8_t);
 
-volatile uint8_t rx_buf[7];
-volatile uint8_t rx_fill = 0xFF;
-volatile uint8_t input[128] = { 0 };
-volatile uint8_t latch[128] = { 0 };
-volatile uint8_t lcd_enabled = 0;
+uint8_t clock_high = 0;
+uint8_t rx_buf[7];
+uint8_t rx_fill = 0xFF;
+uint8_t input[128] = { 0 };
+uint8_t latch[128] = { 0 };
+uint8_t out_offset = 0;
+uint8_t out_bits = 0;
+uint8_t out_fill = 0;
+volatile uint8_t reset_pos = 0xFF;
+uint8_t lcd_enabled = 0;
 uint8_t log_row = 0;
 uint8_t log_col = 0;
 
 int main()
 {
-       uint8_t clock_high = 0;
-       uint8_t bits = 0;
-       uint8_t n_bits = 8;
-       uint8_t offset = 0;
-       uint8_t i;
-
        DDRD = 0x06;   // 00000110
        PORTD = 0xC0;  // 11000000
        DDRB = 0x20;   // 00100000
        PORTB = 0x1F;  // 00011111
+       PCMSK2 = BIT(PCINT19) | BIT(PCINT21);
+       PCICR = BIT(PCIE2);
 
        serial_init(9600);
        lcd_init();
@@ -65,53 +66,20 @@ int main()
 
        while(1)
        {
-               uint8_t b_pins, d_pins;
+               uint8_t i;
 
                check_input();
 
-               b_pins = PINB;
-               d_pins = PIND;
-
-               if(d_pins&BIT(CLOCK))
+               i = reset_pos;
+               if(i!=0xFF)
                {
-                       if(!clock_high)
-                       {
-                               if(d_pins&BIT(LOAD))
-                               {
-                                       offset = 0;
-                                       bits = latch[0];
-                                       n_bits = 8;
-                               }
-                               else
-                               {
-                                       bits >>= 1;
-                                       if(!--n_bits)
-                                       {
-                                               ++offset;
-                                               bits = latch[offset];
-                                               n_bits = 8;
-                                       }
-                               }
-
-                               if(bits&1)
-                                       PORTD |= BIT(DATA_OUT);
-                               else
-                                       PORTD &= ~BIT(DATA_OUT);
-
-                               clock_high = 1;
-                       }
+                       latch[i] = input[i];
+                       if(++i>=sizeof(input))
+                               i = 0xFF;
+                       reset_pos = i;
                }
-               else if(clock_high)
-                       clock_high = 0;
 
-               if(d_pins&BIT(RESET))
-               {
-                       uint8_t i;
-                       for(i=0; i<128; ++i)
-                               latch[i] = input[i];
-               }
-
-               if(b_pins&BIT(LCD_DISABLE))
+               if(PINB&BIT(LCD_DISABLE))
                {
                        if(lcd_enabled)
                        {
@@ -222,3 +190,40 @@ uint8_t decode_hex(uint8_t c)
        else
                return 0;
 }
+
+ISR(PCINT2_vect)
+{
+       uint8_t d = PIND;
+       if(d&BIT(CLOCK))
+       {
+               if(!clock_high)
+               {
+                       if(d&BIT(LOAD))
+                       {
+                               out_offset = 0;
+                               out_bits = latch[0];
+                               out_fill = 8;
+                       }
+
+                       if(out_bits&1)
+                               PORTD |= BIT(DATA_OUT);
+                       else
+                               PORTD &= ~BIT(DATA_OUT);
+
+                       out_bits >>= 1;
+                       if(!--out_fill)
+                       {
+                               ++out_offset;
+                               out_bits = latch[out_offset];
+                               out_fill = 8;
+                       }
+
+                       clock_high = 1;
+               }
+       }
+       else
+               clock_high = 0;
+
+       if(d&BIT(RESET))
+               reset_pos = 0;
+}