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#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;
}
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