arduino-0018-windows

arduino-0018-windows/hardware/tools/avr/doc/avr-libc/examples/demo/demo.c

@@ -0,0 +1,89 @@
+/*
+ * ----------------------------------------------------------------------------
+ * "THE BEER-WARE LICENSE" (Revision 42):
+ * <joerg@FreeBSD.ORG> wrote this file.  As long as you retain this notice you
+ * can do whatever you want with this stuff. If we meet some day, and you think
+ * this stuff is worth it, you can buy me a beer in return.        Joerg Wunsch
+ * ----------------------------------------------------------------------------
+ *
+ * Simple AVR demonstration.  Controls a LED that can be directly
+ * connected from OC1/OC1A to GND.  The brightness of the LED is
+ * controlled with the PWM.  After each period of the PWM, the PWM
+ * value is either incremented or decremented, that's all.
+ *
+ * $Id: demo.c,v 1.9 2006/01/05 21:30:10 joerg_wunsch Exp $
+ */
+
+#include <inttypes.h>
+#include <avr/io.h>
+#include <avr/interrupt.h>
+#include <avr/sleep.h>
+
+#include "iocompat.h"		/* Note [1] */
+
+enum { UP, DOWN };
+
+ISR (TIMER1_OVF_vect)		/* Note [2] */
+{
+    static uint16_t pwm;	/* Note [3] */
+    static uint8_t direction;
+
+    switch (direction)		/* Note [4] */
+    {
+        case UP:
+            if (++pwm == TIMER1_TOP)
+                direction = DOWN;
+            break;
+
+        case DOWN:
+            if (--pwm == 0)
+                direction = UP;
+            break;
+    }
+
+    OCR = pwm;			/* Note [5] */
+}
+
+void
+ioinit (void)			/* Note [6] */
+{
+    /* Timer 1 is 10-bit PWM (8-bit PWM on some ATtinys). */
+    TCCR1A = TIMER1_PWM_INIT;
+    /*
+     * Start timer 1.
+     *
+     * NB: TCCR1A and TCCR1B could actually be the same register, so
+     * take care to not clobber it.
+     */
+    TCCR1B |= TIMER1_CLOCKSOURCE;
+    /*
+     * Run any device-dependent timer 1 setup hook if present.
+     */
+#if defined(TIMER1_SETUP_HOOK)
+    TIMER1_SETUP_HOOK();
+#endif
+
+    /* Set PWM value to 0. */
+    OCR = 0;
+
+    /* Enable OC1 as output. */
+    DDROC = _BV (OC1);
+
+    /* Enable timer 1 overflow interrupt. */
+    TIMSK = _BV (TOIE1);
+    sei ();
+}
+
+int
+main (void)
+{
+
+    ioinit ();
+
+    /* loop forever, the interrupts are doing the rest */
+
+    for (;;)			/* Note [7] */
+        sleep_mode();
+
+    return (0);
+}