switch
switch.c
Switch.c has some new elements added:
//When the switch is pressed, flash the LED off and on.
#define F_CPU 1000000UL // Define software reference clock for delay duration
// Must be write before call delay.h
#include <avr/io.h>
#include <util/delay.h>
#define SWITCH PB1 // Define ext switch pin on PB2 *1
#define LED PB0 // Define ext led pin on PB0 *2
#define BLINK_SPEED 100 //in milliseconds
void delay(int ms) {
int i;
for (i=0; i<ms; i++) {
_delay_ms(1);
}
}
int main(void){
DDRB &= ~(1<<SWITCH); // Set SWITCH pin to input.
DDRB |= (1 << LED); // Set LED pin to output.
while(1){
// Read SWT pin
if (bit_is_clear(PINB, SWITCH)){ //bit_is_clear defined in avr/io.h
while(bit_is_clear(PINB, SWITCH)){; //simple form of debouncing.
PORTB ^= (1 << LED); // Set 0 on LED pin (led turn on)
delay(BLINK_SPEED); // delay BLINK_SPEED milliseconds
}
//the while loop catches the input once.
}
else{
PORTB &= ~(1 << LED); // Set 1 on LED pin (led turn off)}
//once the switch is set and it still is being held
//maintain the state of the switch.
while(bit_is_set(PINB, SWITCH)){};
}
}
return 0;
}
components
To get the ATtiny to read the value of a switch, we can leave in place everything on the breadboard blink.c except add a few more components.
(NO in the context of a switch stands for Normally Open.)
Here's another video:
Next...
We will get an LED's frequency of blink tied to an analog input.
![[paper clip]](/courses/source/wiki_images/paper_clip_tilt.png)
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