Minimal encoder input handling

It is now possible to act on the encoders input. No effort regarding
debouncing and dechattering has been done yet.

firmware/src/main.c

@@ -1,6 +1,7 @@
 #define	F_CPU   8000000UL
 
 #include <avr/io.h>
+#include <avr/interrupt.h>
 #include <util/delay.h>
 #include <stdbool.h>
 
@@ -13,6 +14,9 @@
 #define LCD_CD PB0
 #define LCD_RST PB1
 
+#define ENC_A (PINB & (1 << PB6))
+#define ENC_B (PINB & (1 << PB7))
+
 const uint8_t splash[] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x80, 0xC0, 0xE0, 0xF0, 0xF0, 0xF8, 0xFC, 0xFC, 0xFE, 0xFE, 0xFE, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFE, 0xFE, 0xFE, 0xFC, 0xFC, 0xF8, 0xF0, 0xF0, 0xE0, 0xC0, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
                           0x00, 0x00, 0x00, 0x00, 0x80, 0xF0, 0xFC, 0xFE, 0xFF, 0xFF, 0x7F, 0x3F, 0x1F, 0x3F, 0x3F, 0x7F, 0x7F, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x7F, 0x1F, 0x0F, 0x0F, 0x07, 0x07, 0x07, 0x03, 0xC3, 0xE3, 0x73, 0x37, 0x17, 0x07, 0x0F, 0x1E, 0x3C, 0xF0, 0x80, 0x00, 0x00, 0x00, 0x00,
                           0x00, 0x00, 0x00, 0x00, 0xFF, 0xFF, 0xFF, 0xE7, 0xC3, 0x81, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0xFF, 0xFF, 0xFF, 0xFF, 0x0F, 0x00, 0x00, 0xFC, 0xFE, 0xFE, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFE, 0xFC, 0x30, 0x00, 0x00, 0xFF, 0x00, 0x00, 0x00, 0x00,
@@ -21,6 +25,8 @@ const uint8_t splash[] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x80,
                           0xE0, 0x60, 0xE0, 0x00, 0x00, 0xE0, 0x60, 0xE0, 0x00, 0x00, 0xE0, 0x60, 0xF8, 0x00, 0x00, 0xE0, 0xA0, 0xE0, 0x00, 0x00, 0xE0, 0x20, 0x60, 0x00, 0x00, 0xE0, 0xA0, 0xA0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xE0, 0x60, 0xE0, 0x00, 0x00, 0xE0, 0x20, 0x60, 0x00, 0x00, 0xE0, 0x60, 0xE0,
                           0x03, 0x02, 0x03, 0x00, 0x00, 0x03, 0x00, 0x03, 0x00, 0x00, 0x03, 0x02, 0x03, 0x00, 0x00, 0x03, 0x02, 0x02, 0x00, 0x00, 0x03, 0x00, 0x00, 0x00, 0x00, 0x02, 0x02, 0x03, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x03, 0x02, 0x03, 0x00, 0x00, 0x03, 0x00, 0x00, 0x00, 0x00, 0x0B, 0x0A, 0x0F};
 
+static uint8_t enc = 0;
+
 void spi_init(void) {
     SPI_DDR |= (1 << SPI_SCK) | (1 << SPI_MOSI) | (1 << SPI_SS);
     SPI_PORT |= (1 << SPI_SS);
@@ -86,32 +92,69 @@ void lcd_splash() {
     }
 }
 
+// Encoder rotation interrupt
+ISR(PCINT0_vect) {
+    cli();
+
+    switch(enc) {
+    case 0:
+        if (ENC_A && !ENC_B)
+            enc = 1;
+        else if (!ENC_A && ENC_B)
+            enc = 3;
+        break;
+    case 1:
+        if (ENC_A && ENC_B) {
+            enc = 2;
+        } else if (!ENC_A && !ENC_B) {
+            enc = 0;
+        }
+        break;
+    case 2:
+        if (!ENC_A && ENC_B)
+            enc = 3;
+        else if (ENC_A && !ENC_B)
+            enc = 1;
+        break;
+    case 3:
+        if (!ENC_A && !ENC_B) {
+            enc = 0;
+        } else if (ENC_A && ENC_B) {
+            enc = 2;
+        }
+        break;
+    }
+
+    // TODO: proper debounce and dechattering
+    _delay_us(100);
+
+    sei();
+}
+
 int main(void) {
     // FastPWM: 1.25kHz
+    // TODO: Try to get the backlit even more dim
     TCCR0A = (1 << WGM01) | (1 << WGM00) | (1 << COM0B1);
     TCCR0B = (1 << CS01) | (1 << WGM02); // prescaler = 8;
     OCR0A = 100;
-    OCR0B = 10;
+    OCR0B = 0;
     DDRD |= (1 << PD5);
 
-    bool reverse = 0;
+    // SPI setup
-
     spi_init();
     lcd_init();
+
+    // Encoder setup
+    PORTB |= (1 << PB6) | (1 << PB7);
+    PCICR |= (1 << PCIE0);
+    PCMSK0 |= (1 << PCINT6) | (1 << PCINT7);
+
+    // Show splash screen
     lcd_splash();
 
-    while (1) {
+    // Enable interrupts
-        _delay_ms(1);
+    sei();
 
-        if (OCR0B > 100)
+    // Run...
-            reverse = !reverse;
+    for (;;);
-
-        if (reverse)
-            OCR0B++;
-        else
-            if (OCR0B > 0)
-                OCR0B--;
-            else
-                reverse = !reverse;
-    }
 }