Recalibrated timings for 16Mz clock. Added docs.

.gitignore

@@ -2,4 +2,5 @@
 *.git
 *.o
 *.elf
-*.d
+*.d
+*.hex

Makefile

@@ -43,7 +43,7 @@ AVRDUDE = avrdude $(PROGRAMMER) -p $(DEVICE) -B 10 -F
 COMPILE = avr-gcc -Wall -Os -DF_CPU=$(CLOCK) -mmcu=$(DEVICE) -I. -ffunction-sections --std=c99
 
 # symbolic targets:
-all:	chord.hex
+all:	reverse.hex
 
 .c.o:
 	$(COMPILE) -c $< -o $@
@@ -60,7 +60,7 @@ all:	chord.hex
 	$(COMPILE) -S $< -o $@
 
 flash:	all
-	$(AVRDUDE) -U flash:w:chord.hex:i
+	$(AVRDUDE) -U flash:w:reverse.hex:i
 
 fuse:
 	$(AVRDUDE) $(FUSES)
@@ -70,18 +70,18 @@ install: flash fuse
 
 # if you use a bootloader, change the command below appropriately:
 load: all
-	bootloadHID chord.hex
+	bootloadHID reverse.hex
 
 clean:
-	rm -f chord.hex main.elf $(OBJECTS) $(OBJECTS:.o=.d)
+	rm -f reverse.hex main.elf $(OBJECTS) $(OBJECTS:.o=.d)
 
 # file targets:
 main.elf: $(OBJECTS)
 	$(COMPILE) -o main.elf $(OBJECTS) -lm -Wl,--gc-sections
 
-chord.hex: main.elf
-	rm -f chord.hex
-	avr-objcopy -j .text -j .data -O ihex main.elf chord.hex
+reverse.hex: main.elf
+	rm -f reverse.hex
+	avr-objcopy -j .text -j .data -O ihex main.elf reverse.hex
 	avr-size -C --mcu=$(DEVICE) main.elf
 # If you have an EEPROM section, you must also create a hex file for the
 # EEPROM and add it to the "flash" target.

README.md

@@ -1,3 +1,18 @@
-A quick rebuild of David Carne's *Reverse Engineering the iPod Shuffle 3G headphone remote protocol* from http://david.carne.ca/shuffle_hax/shuffle_remote.html for the stock Arduino Atmega 328 clocked to 16Mhz
+# Reverse shuffle
+
+A quick recalibration of David Carne's *Reverse Engineering the iPod Shuffle 3G headphone remote protocol* from http://david.carne.ca/shuffle_hax/shuffle_remote.html for the stock Arduino Atmega 328 clocked to 16Mhz.
+
+## To compile and write
+
+* Get avrdude and avr-gcc
+* Attach AVR-ISP to ISP-port
+* Compile with 'make'
+* Flash with 'make flash'
+* Signal appears on PIN5 on the Arduino (PortB, pin 5)
+
+If avrdude can't find your programmer try editing the makefile l.33 
+
+PROGRAMMER ?= -c avrisp2 -P usb
+
+to point to where the programmer actually show up, /dev/something, instead of just usb.
 
-WIP

main.c

@@ -6,9 +6,20 @@
 #define CTL_PIN (1<<5)
 #define CTL_HI (!(ACSR & (1<<ACO)))
 
+#define BLINK_DELAY_MS 100
+
+
 void main()
 {
 
+  // Flash LED once for debug
+  DDRB |= _BV(DDB5);
+  PORTB |= _BV(PORTB5);
+  _delay_ms(BLINK_DELAY_MS);
+
+  PORTB &= ~_BV(PORTB5);
+
+
   CLKPR = 0x80;
   CLKPR = 0x0;
   ADCSRB &= ~(1<< ACME);
@@ -25,15 +36,15 @@ void main()
     PORTC |= CTL_PIN;
     _delay_ms(4.2);
 
-    // 280khz burst
+    // 280khz burst (scoped at 277khz)
     TCCR0A = 0x23;
     TCNT0 = 0x0;
-    OCR0A = 27;
+    OCR0A = 56;
     DDRD |= 1<<5;
     _delay_ms(1.5);
 
-    // 245khz burst
-    OCR0A = 33;
+    // 245khz burst (scope at 247khz)
+    OCR0A = 63;
     TCNT0 = 0x0;
     _delay_ms(4.6);