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--- de:examples:digi:io [2009/04/27 17:52] – nierhoff
+++ de:examples:digi:io [2020/07/20 12:00] (current) – external edit 127.0.0.1
@@ Line 1: / Line 1: @@
+====== Input/Output am Study Board ======
+{{:et:naited:digi:io.jpg?300|}}
+Study Board ‚Basic’ verfügt über drei Outputs (LEDs, verbunden mit PORT-C[3..5]) und drei Inputs (Mikroschalter an PORT-C[0..2]).
+Dieses Beispiel zeigt wie die LEDs beim Drücken des entsprechenden Schalters aktiviert werden.
+==== Schaltplan: ====
+{{:et:harjutused:digi:1a_skeem.jpg?500|}}
+==== Beispiel C Code: ====
+<code c>
+/* Labor 1 example
+Description: Example works with Studyboard Basic v3
+Press S1 - LED1 goes ON; S2 - LED2 goes ON; S3 - LED3 goes ON
+LED = 0 (ON)  	LED = 1 (OFF)
+S= 0 (ON) 	S= 1 (OFF)
+PORT direction: 1-output	0-input
+Author: Raivo Sell 2008
+*/
+#include <avr/io.h>
+#define F_CPU 14745600UL
+//Definitions for easier bit manipulations
+#define SET(x) |= (1<<x)  //bit high in port x
+#define CLR(x) &=~(1<<x)  //bit low in port x
+int main(void) { //main program
+    DDRC  = 0x38;  // DDRC  0bXX111000
+    PORTC = 0x3F;  // PORTC 0bXX111111
+	//endless loop
+	while(1) {
+		// if button is pressed (pin is low)
+		if (bit_is_clear(PINC, 0))	//Switch S1
+			PORTC CLR(3); //LED 1 ON
+		else if (bit_is_clear(PINC, 1))//Switch S2
+			PORTC CLR(4); //LED 2 ON
+		else if (bit_is_clear(PINC, 2))//Switch S3
+			PORTC CLR(5); //LED 3 ON
+		else // If nothing is pressed
+			PORTC=0xFF;		//All LEDs OFF (LED=1)
+	}
+}
+</code>
+==== Beispiel (Kurzversion) ====
+<code c>
+/* Lab 1 example
+Author: Maido Hiiemaa
+Date: 2009
+*/
+#include <avr/io.h>
+int main(void) {
+     DDRC  = 0x38;  //  (00111000)
+     while(1) {
+        PORTC &= ~((PINC << 3) | 0xC7 ); // zeros
+	PORTC |= ((PINC << 3) & ~0xC7 ); // ones
+        }
+}
+</code>
+==== Elliminating bouncing ====
+Source: [[http://www.micahcarrick.com/05-15-2006/avr-tutorial-switch-debounce.html|Micah Carrick tutorial]]
+<code c>
+#include <avr/io.h>
+#include <util/delay.h>
+#define BUTTON_PORT PORTC       /* PORTx - nupu register */
+#define BUTTON_PIN PINC         /* PINx - nupu sisendi register */
+#define BUTTON_BIT PC0          /* nupu sisend/väljund bit */
+int button_is_pressed()
+{
+        /* button is on when BIT is low (0) */
+        if (bit_is_clear(BUTTON_PIN, BUTTON_BIT))
+        {
+                _delay_ms(25); /* de-bouncing delay time */
+                if (bit_is_clear(BUTTON_PIN, BUTTON_BIT)) return 1;
+        }
+        return 0;
+}
+int main (void){
+        /* switch on internel pull-ups */
+        BUTTON_PORT |= _BV(BUTTON_BIT);
+        if (button_is_pressed()){
+                        //  do somthing
+                        // wait if needed
+        }
+}
+</code>