Accurate with 16MHz crystal

Makefile

@@ -1,4 +1,6 @@
 ARCH = avr
 
+CFLAGS += -DARCH=$(ARCH)
+
 include Makefile.$(ARCH)
 

Makefile.avr

@@ -1,19 +1,20 @@
 PROG = main
 
-MCU = atmega328p
+MCU = attiny84
 
 CC = avr-gcc
 CFLAGS += -mmcu=$(MCU)
-CFLAGS += -DF_CPU=16000000UL
 CFLAGS += -Os
 CFLAGS += -w
 
 LDFLAGS += -mmcu=$(MCU)
 
-AVDFLAGS += -p m328p
+AVDFLAGS += -p $(MCU)
-AVDFLAGS += -c arduino
+AVDFLAGS += -c usbtiny
-AVDFLAGS += -b 115200
+
-AVDFLAGS += -P /dev/ttyACM0
+FUSES += -U lfuse:w:0x7f:m
+FUSES += -U hfuse:w:0xd9:m
+FUSES += -U efuse:w:0xff:m
 
 
 upload: .upload
@@ -22,6 +23,9 @@ upload: .upload
 	avrdude $(AVDFLAGS) -U flash:w:$<
 	touch $@
 
+fuses:
+	avrdude $(AVDFLAGS) $(FUSES)
+
 $(PROG).hex: $(PROG)
 	avr-objcopy -O ihex -R .eeprom -R .fuse -R .lock -R .signature $< $@
 

avr.c

@@ -13,12 +13,12 @@ extern volatile uint32_t jiffies;
 // Count microseconds
 volatile uint32_t micros = 0;
 
-// Interrupt called every 1024 µs
+// Interrupt called every 256 * 64 microseconds
-SIGNAL(TIMER0_OVF_vect)
+ISR(TIM0_OVF_vect)
 {
 	uint32_t m = micros;
 	
-	m += 1024;
+	m += (256 * 64);
 	if (m >= JIFFY_uS) {
 		m %= JIFFY_uS;
 		tick = true;
@@ -28,33 +28,25 @@ SIGNAL(TIMER0_OVF_vect)
 }
 
 
-#define mode(on) bit(PORTD, _BV(0), on)
-#define sin(on) bit(PORTD, _BV(1), on)
-#define sclk(on) bit(PORTD, _BV(2), on)
-#define xlat(on) bit(PORTD, _BV(3), on)
-// Connect GSCLK to SCLK
-// Connect BLANK to XLAT
-// TRUST ME, THIS TOTALLY WORKS
-
-#define nesclk(on) bit(PORTD, _BV(4), on)
-#define nesltch(on) bit(PORTD, _BV(5), on)
-#define nesout() ((PIND & _BV(6)) << 6)
-
 void
 init(void)
 {
+	// Set prescaler to 16, so we get clock ticks at exactly 1MHz
+	CLKPR = _BV(CLKPCE);
+	CLKPR = 0x04;
+
 	// Set timer 0 interrupt clock divider to 64
-	TCCR0B = 0x03;
+	TCCR0B = _BV(CS01) + _BV(CS00);
 
 	// enable timer 0 overflow interrupt
-	TIMSK0 = 0x01;
+	TIMSK0 |= _BV(TOIE0);    //enable compare match interrupt;
 	
 	// Enable interrupts
 	sei();
 
-	DDRD = ~(_BV(NESOUT));
+	DDRA = ~(_BV(NESOUT));
 	DDRB = 0xff;
 
-	PORTD = 0;
+	PORTA = 0;
-	
+	PORTB = 0xff;
 }

avr.h

@@ -5,24 +5,25 @@
 #include <avr/io.h>
 #include <avr/interrupt.h>
 
+
 // Make sure JIFFY_uS is going to be an integer and not a float!
-#define JIFFIES_PER_SECOND 50
+#define JIFFIES_PER_SECOND 100
-#define JIFFY_uS (1000000 / JIFFIES_PER_SECOND)
+#define JIFFY_uS (10000000 / JIFFIES_PER_SECOND)
 
 #define bit(pin, bit, on) pin = (on ? (pin | bit) : (pin & ~bit))
 
-#define mode(on) bit(PORTD, _BV(0), on)
+#define mode(on) bit(PORTA, _BV(0), on)
-#define sin(on) bit(PORTD, _BV(1), on)
+#define sin(on) bit(PORTA, _BV(1), on)
-#define sclk(on) bit(PORTD, _BV(2), on)
+#define sclk(on) bit(PORTA, _BV(2), on)
-#define xlat(on) bit(PORTD, _BV(3), on)
+#define xlat(on) bit(PORTA, _BV(3), on)
 // Connect GSCLK to SCLK
 // Connect BLANK to XLAT
 // TRUST ME, THIS TOTALLY WORKS
 
 #define NESOUT 6
-#define nesclk(on) bit(PORTD, _BV(4), on)
+#define nesclk(on) bit(PORTA, _BV(4), on)
-#define nesltch(on) bit(PORTD, _BV(5), on)
+#define nesltch(on) bit(PORTA, _BV(5), on)
-#define nesout() ((PIND & _BV(NESOUT)) << NESOUT)
+#define nesout() ((PINA & _BV(NESOUT)) << NESOUT)
 
 void init(void);
 

blink.c

@@ -15,10 +15,10 @@ int main (void)
  
       /* wait (10 * 120000) cycles = wait 1200000 cycles */
       counter = 0;
-      while (counter != 50)
+      while (counter != 10)
 	{
 	  /* wait (30000 x 4) cycles = wait 120000 cycles */
-	  _delay_loop_2(60000);
+	  _delay_loop_2(30000);
 	  counter++;
 	}
  
@@ -27,7 +27,7 @@ int main (void)
  
       /* wait (10 * 120000) cycles = wait 1200000 cycles */
       counter = 0;
-      while (counter != 50)
+      while (counter != 10)
 	{
 	  /* wait (30000 x 4) cycles = wait 120000 cycles */
 	  _delay_loop_2(30000);

main.c

@@ -5,7 +5,7 @@
 #include <avr/io.h>
 #include <util/delay.h>
 
-#if defined (__AVR_ATmega328P__)
+#if ARCH == avr
 #  include "avr.h"
 #else
 #  include "ti.h"
@@ -249,6 +249,7 @@ loop()
 		update_controller();
 
 		if (jiffies % (JIFFIES_PER_SECOND / 10) == 0) {
+		PORTB ^= 0xff;
 			switch (state) {
 			case SETUP:
 				break;