1 files changed, 61 insertions, 0 deletions
diff --git a/timebase.c b/timebase.c
new file mode 100644
index 0000000..3b97e2b
--- /dev/null
+++ b/timebase.c
@@ -0,0 +1,61 @@
+#include "main.h"
+#include "timebase.h"
+
+							      // at 12MHz:
+#define T0COUNT     (XTAL / 1024 / 64)	                         // 183
+#define T0SECERR    (XTAL - 1024L * 64 * T0COUNT)	         // 6912
+#define T0COUNTSEC  (T0COUNT + T0SECERR / 1024)	                 // 189
+#define T0MINERR    (XTAL - 1024 * (63 * T0COUNT + T0COUNTSEC))  // 768
+#define T0COUNTMIN  (T0COUNTSEC + (T0MINERR * 60 + 512) / 1024)  // 234
+
+// 234 = 12000000 Hz
+// 233 = 12000017 Hz = 4s/month
+
+
+u8 timeflags;
+u8 dcf77_period;
+u8 dcf77_pulse;
+u8 ct_64Hz;					// 64 Hz counter (4sec)
+
+
+void timebase_init( void )
+{
+  TCCR0 = 1<<CS02^1<<CS00;			// prescale = 1024
+  TIMSK = 1<<TOIE0;				// interrupt enable
+}
+
+
+SIGNAL (SIG_OVERFLOW0)
+{
+  static u8 dcf77_time, old_dcf77;
+					// DCF77 receive
+  if( dcf77_time != 0xFF )			// stop on 0xFF
+    dcf77_time++;				// count ticks
+  if( (DCF77_PIN ^ old_dcf77) & 1<<DCF77 ){	// pin changed ?
+    old_dcf77 ^= 0xFF;				// change old flag
+    if( old_dcf77 & 1<<DCF77 ){
+      dcf77_period = dcf77_time;		// store ticks of period
+      dcf77_time = 0;				// count next period
+    }else{
+      dcf77_pulse = dcf77_time;			// store ticks of pulse
+    }
+  }
+					// time base 1 second
+  TCNT0 = (u16)(256 - T0COUNT);			// reload per tick: -183
+  if( ++ct_64Hz & 0x3F ){			// 64 ticks = one second
+    timeflags = 1<<ONE_TICK;			// one tick over
+    return;
+  }
+  TCNT0 = (u16)(256 - T0COUNTSEC);		// reload per second: -189
+  if( timeflags & (1<< ONE_MINUTE ))
+    TCNT0 = (u16)(256 - T0COUNTMIN);		// reload per minute: -234
+  timeflags = 1<<ONE_SECOND^1<<ONE_TICK;	// one tick, one second over
+}
+
+
+void sync_sec( void )			// synchronize by DCF77
+{
+  TCNT0 = (u16)(256 - T0COUNTMIN);
+  ct_64Hz = 0;
+  timeflags = 0;
+}