85 lines
2.5 KiB
C
85 lines
2.5 KiB
C
#include <avr/io.h>
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// #include <util/delay.h>
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#define SET(REGISTER, BIT) REGISTER |= 1 << BIT
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#define CLEAR(REGISTER, BIT) REGISTER &= ~(1 << BIT)
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#define TEST(REGISTER, BIT) REGISTER & 1 << BIT
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#define TOGGLE(REGISTER, BIT) REGISTER ^= 1 << BIT
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#define D1 0
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#define D2 1
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#define D3 2
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#define D4 4
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int main()
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{
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// registers :
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// DDRx : (Data Direction Register) Controls whether each pin is an input or output
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// - 1 = output (pull-up off)
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// - 0 = input
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// PORTx : (Port Data Register)
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// if DDRx = 1 (output mode) : Controls the output state of a pin when it's configured as an output
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// - 1 = HIGH (5V?) (VCC)
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// - 0 = LOW (0V) (GND)
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// if DDRx = 0 (input mode) : Controls the internal pull-up resistor when the pin is an input
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// - 1 = pull-up on
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// - 0 = pull-up off (pin floats)
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// PINx : (Pin Input Register) Reads the current logical state of a pin
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// Reflects the actual voltage on the pin
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// Special feature: Writing 1 to PINxn toggles the corresponding PORTxn bit (regardless of DDRx)
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// turns on led 1
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SET(DDRB, D1); // make PB0 as OUTPUT (pullup is off)
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SET(PORTB, D1); // make PB0 as HIGH (LED turns ON)
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// SET(DDRB, D2); // make PB1 as OUTPUT (pullup is off)
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// CLEAR(PORTB, D2); // make PB1 as LOW (LED turns OFF)
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// CLEAR(DDRB, D3); // make PB2 as INPUT
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// SET(PORTB, D3); // make PB2 pullup on
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// CLEAR(DDRB, D4); // make PB4 as INPUT
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// CLEAR(PORTB, D4); // make PB4 pullup off
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////////////////////////////////
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// TEST weird behavior of PIN register :
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// in initial tests, using PIN register to toggle ON two leds only worked for the second one
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// after some tests, this behavior is not anymore
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//
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// test 1 : only led 3 turns on
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// SET(DDRB, D1);
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// CLEAR(PORTB, D1);
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// SET(PINB, D1);
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// SET(DDRB, D3);
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// CLEAR(PORTB, D3);
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// SET(PINB, D3);
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//
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// test 2 : only led 3 turns on
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// SET(DDRB, D1);
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// CLEAR(PORTB, D1);
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// SET(DDRB, D3);
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// CLEAR(PORTB, D3);
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// SET(PINB, D1);
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// SET(PINB, D3);
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//
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// test 3 : both leds turns on
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// SET(DDRB, D1);
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// CLEAR(PORTB, D1);
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// SET(DDRB, D3);
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// CLEAR(PORTB, D3);
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// PINB = (1 << D1) | (1 << D3);
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//
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// test 4 : both leds turns on
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// SET(DDRB, D1);
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// CLEAR(PORTB, D1);
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// SET(DDRB, D3);
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// CLEAR(PORTB, D3);
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// SET(PINB, D1);
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// _delay_us(500);
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// SET(PINB, D3);
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//
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////////////////////////////////
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return 0;
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} |