add source for PIR sensor buzzer project12

project12/makefile

@@ -0,0 +1,3 @@
+
+pirbuzzer: pirbuzzer.c
+	cc -o pirbuzzer pirbuzzer.c -lwiringPi

project12/pirbuzzer.c

@@ -0,0 +1,35 @@
+
+#include <stdio.h>
+#include <wiringPi.h>
+
+int main (void)
+{
+	const int BuzzerPin = 1;     // buzzer is attached Pin #1 or BCM #18
+	const int PirSensorPin = 0;  // PIR sensor is attached Pin #0 or BCM #17
+	int alarmState;              // current alarm state to reduce output lines.
+
+	if (wiringPiSetup() == -1) {
+		printf ("setup of wiringPi lib failed.\n");
+		return 1;
+	}
+
+	pinMode (BuzzerPin, OUTPUT);
+	pinMode (PirSensorPin, INPUT);
+
+	alarmState = 0;
+	printf (" --  No alarm\n");
+	while (1) {
+		if (digitalRead (PirSensorPin) == 0) {
+			digitalWrite (BuzzerPin, HIGH);
+			alarmState == 1 && printf (" --  No alarm\n");
+			alarmState = 0;
+		} else {
+			digitalWrite (BuzzerPin, LOW);
+			alarmState == 0 && printf ("***  Alarm!\n");
+			alarmState = 1;
+		}
+		delay(1000);
+	}
+
+	return 0;
+}