AVR Lesson: Output Pins I
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Goals
In this lesson, you'll program the micro-controller version of "hello world", letting you fire up your programmer, compiler, chip, LED, and test them all out. You'll learn how to setup and use pins for output, and along the way get some exposure to AVR-specific coding practice.
The Circuit
The Code
/* Blinker Demo */ #include <avr/io.h> /* Defines pins, ports, etc */ #define F_CPU 1000000UL /* Sets up the chip speed for delay.h */ #include <util/delay.h> /* Functions to waste time */ #define LED PB4 /* Defines pin PB4 for the LED. I often include a bunch of the circuit info in the code this way, which makes porting the code to another chip easier and reminds you of how to hook it up. */ int main(void){ DDRB = _BV(LED); /* Data Direction Register B: writing a one to the bit enables output. More on the _BV() macro in the next lesson.*/ while(1){ /* the main loop, from which we never return */ PORTB = _BV(LED); /* Turn on the LED bit/pin in PORTB */ _delay_ms(400); /* wait */ PORTB &= ~_BV(LED); /* Turn off the LED bit/pin in PORTB */ _delay_ms(400); /* wait */ } return(0); /* never reached */ }
Trouble?
Programmer woes:
Is the LED in the correct polarity? (Positive to pin PB4, negative to GND).
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