56 lines
1.8 KiB
C
56 lines
1.8 KiB
C
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/******************************************************************************
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Title: Turn on LED when switch is pressed
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Author: Peter Fleury <pfleury@gmx.ch> http://jump.to/fleury
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Date: December 2002
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Software: AVR-GCC 3.3
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Hardware: AT90S8515 at 4 Mhz, STK200 compatible starter kit
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Description:
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This example demonstrates basic port input/output technic.
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If one of the switches on port D is pressed, the corresponding LED on port B is
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turned on.
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*******************************************************************************/
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#include <inttypes.h>
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#include <avr/io.h>
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int main(void)
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{
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uint8_t led;
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uint8_t keys;
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DDRB = 0xff; // use all pins on PortB for output
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DDRD = 0x00; // use all pins on port D for input
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PORTD = 0xff; // activate internal pull-up
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PORTB = 0xff; // set output high -> turn all LEDs off
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for (;;) { // loop forever
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keys = ~PIND; // read input port with switches (active-low)
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if ( keys & 1 )
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led = 1;
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else if ( keys & 2 ) // priority encoder: if multiple switches are pressed,
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led = 2; // only the lowest switch is recognized
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else if ( keys & 4 )
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led = 4;
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else if ( keys & 8 )
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led = 8;
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else if ( keys & 0x10 )
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led = 0x10;
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else if ( keys & 0x20 )
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led = 0x20;
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else if ( keys & 0x40 )
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led = 0x40;
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else if ( keys & 0x80 )
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led = 0x80;
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else
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led = 0;
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if ( keys )
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PORTB = ~led; // Set corresponding LED if switch pressed
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}
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}
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