Arduino Experiment: Playing with Inline Assembler

What started with the need to embed a single assembly language instruction in an Arduino sketch, became a complete flashing LED program written in AVR assembler.

ATmega328P Pin Mapping: http://arduino.cc/en/Hacking/PinMapping168#.UyMGKPl_tV4

AVR ATmega328P Data Sheet www.atmel.com/Images/doc8161.pdf‎

Inline Assembler Cookbook: http://www.nongnu.org/avr-libc/user-manual/inline_asm.html

What registers are used by the C compiler?: http://www.nongnu.org/avr-libc/user-manual/FAQ.html#faq_reg_usage

This guy did it properly: http://ucexperiment.wordpress.com/

Arduino sketch:

void setup() { asm("sbi 0x04, 5"); }

void loop() { asm("start:"); asm("sbi 0x05, 5"); asm("ldi r16,40 \n\t rcall delay"); asm("cbi 0x05, 5"); asm("ldi r16,40 \n\t rcall delay");
asm("rjmp start"); asm("delay:"); asm("dec r8"); asm("brne delay"); asm("dec r9"); asm("brne delay"); asm("dec r16"); asm("brne delay"); asm("ret"); } ... https://www.youtube.com/watch?v=TOqnijfi9eI