Skip to content

fix to enable RTC millis() function #583

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
wke67 wants to merge 3 commits into
base: master
Choose a base branch
from
Open

fix to enable RTC millis() function #583

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
dbcdf79
fix to enable RTC millis() function
Oct 18, 2025
facc632
Merge branch 'SpenceKonde:master' into rtc-fix
wke67 Nov 9, 2025
17e5e8b
Merge branch 'SpenceKonde:master' into rtc-fix
wke67 Nov 19, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 1 addition & 1 deletion megaavr/cores/dxcore/core_parameters.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -115,7 +115,7 @@
defined(MILLIS_USE_TIMERA1) || defined(MILLIS_USE_TIMERA2) || defined(MILLIS_USE_TIMERE0) || defined(MILLIS_USE_TIMERA0))
#error "MILLIS_USE_TIMERF0 and another timer are set as the millis timer. Specify one only. If this occurred on the Arduino IDE, please report it promptly."
#endif
#if defined(MILLIS_USE_TIMERD0) || defined(MILLIS_USE_TIMERRTC) || defined(MILLIS_USE_TIMERRTC_XTAL)
#if defined(MILLIS_USE_TIMERD0)
#error "A millis timer not supported on this core was passed. this should only be possible on third party IDEs. "
#endif
#if defined(UARTBAUD5V) || defined(UARTBAUD3V)
Expand Down
2 changes: 1 addition & 1 deletion megaavr/cores/dxcore/timers.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -12,7 +12,7 @@

#ifdef MILLIS_USE_TIMERNONE
#define DISABLE_MILLIS
#elif (defined(MILLIS_USE_TIMERRTC_XTAL) || defined(MILLIS_USE_TIMERRTC_XOSC))
#elif (defined(MILLIS_USE_TIMERRTC_XTAL) || defined(MILLIS_USE_TIMERRTC_XOSC) || defined(MILLIS_USE_TIMERRTC_OSC))
#define MILLIS_USE_TIMERRTC
#elif (defined(MILLIS_USE_TIMERA0) || defined(MILLIS_USE_TIMERA1))
#define MILLIS_USE_TCA
Expand Down
59 changes: 31 additions & 28 deletions megaavr/cores/dxcore/wiring.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -37,7 +37,8 @@ void init_timers();
#error "CLOCK_SOURCE not defined. Must be 0 for internal, 1 for crystal, or 2 for external clock"
#endif

#if !(defined(MILLIS_USE_TIMERNONE) || defined(MILLIS_USE_TIMERB0) || defined(MILLIS_USE_TIMERB1) || defined(MILLIS_USE_TIMERB2) || defined(MILLIS_USE_TIMERB3) || defined(MILLIS_USE_TIMERB4) || defined(MILLIS_USE_TIMERB5) || defined(MILLIS_USE_TIMERA0) || defined(MILLIS_USE_TIMERA1))
#if !(defined(MILLIS_USE_TIMERNONE) || defined(MILLIS_USE_TIMERB0) || defined(MILLIS_USE_TIMERB1) || defined(MILLIS_USE_TIMERB2) || defined(MILLIS_USE_TIMERB3) || defined(MILLIS_USE_TIMERB4) || defined(MILLIS_USE_TIMERB5) || defined(MILLIS_USE_TIMERA0) || defined(MILLIS_USE_TIMERA1) \
|| defined(MILLIS_USE_TIMERRTC_XTAL) || defined(MILLIS_USE_TIMERRTC_XOSC) || defined(MILLIS_USE_TIMERRTC_OSC))
#error "wiring.c test of millis defines failed - no millis timer defined but millis enabled!"
#endif

Expand Down Expand Up @@ -393,7 +394,8 @@ void init_timers();
SREG = oldSREG;
m = (m << 16);
m += rtccount;
m = m - (m >> 5) + (m >> 7);
uint8_t round=( (m&0x3f) + ((m&0x7f)>>1) + 32)>>6;
m = m - (m >> 6) - (m >> 7) - round; // * 1000/1024 -> * ( 1 - 24/1024 ) -> * ( 1 - 1/64 - 1/128 )
/* the compiler is incorrigible - it cannot be convinced not to copy m twice, shifting one 7 times and the other 5 times
* and wasting 35 clock cycles and several precious instruction words.
* What you want is for it to make one copy of m, shift it right 5 places, subtract, then rightshift it 2 more.
Expand Down Expand Up @@ -1782,20 +1784,26 @@ void __attribute__((weak)) init_millis()
TCD0.CTRLC = 0x80;
TCD0.INTCTRL = 0x01; // enable interrupt
TCD0.CTRLA = TIMERD0_PRESCALER | 0x01; // set clock source and enable!
#elif defined(MILLIS_USE_TIMERRTC)
while(RTC.STATUS); // if RTC is currently busy, spin until it's not.
// to do: add support for RTC timer initialization
RTC.PER = 0xFFFF;
#ifdef MILLIS_USE_TIMERRTC_XTAL
_PROTECTED_WRITE(CLKCTRL.XOSC32KCTRLA,0x03);
RTC.CLKSEL = 2; // external crystal
#else
_PROTECTED_WRITE(CLKCTRL.OSC32KCTRLA,0x02);
// RTC.CLKSEL=0; this is the power on value
#endif
RTC.INTCTRL = 0x01; // enable overflow interrupt
RTC.CTRLA = (RTC_RUNSTDBY_bm|RTC_RTCEN_bm|RTC_PRESCALER_DIV32_gc);//fire it up, prescale by 32.
*/
*/
#elif defined(MILLIS_USE_TIMERRTC)
while(RTC.STATUS); // if RTC is currently busy, spin until it's not.
RTC.PER = 0xFFFF;
#if defined(MILLIS_USE_TIMERRTC_XTAL)
// crystal oscillator - startup can take up to 1000ms
_PROTECTED_WRITE(CLKCTRL.XOSC32KCTRLA,(CLKCTRL_RUNSTDBY_bm|CLKCTRL_CSUT_16K_gc|CLKCTRL_LPMODE_bm|CLKCTRL_ENABLE_bm));
RTC.CLKSEL = 2; // RTC_CLKSEL_XOSC32K_gc or RTC_CLKSEL_XTAL32K_gc : external crystal
#elif defined(MILLIS_USE_TIMERRTC_XOSC)
// external clock input on pin xtal32k1
_PROTECTED_WRITE(CLKCTRL.XOSC32KCTRLA,(CLKCTRL_RUNSTDBY_bm|CLKCTRL_SEL_bm|CLKCTRL_ENABLE_bm));
RTC.CLKSEL = RTC_CLKSEL_EXTCLK_gc; // external clock input
#else
// internal 32 kHz oscillator
_PROTECTED_WRITE(CLKCTRL.OSC32KCTRLA,CLKCTRL_RUNSTDBY_bm);
// RTC.CLKSEL=RTC_CLKSEL_OSC32K_gc; 0: this is the power on value
#endif
RTC.INTCTRL = RTC_OVF_bm; // enable overflow interrupt
RTC.CTRLA = (RTC_RUNSTDBY_bm|RTC_RTCEN_bm|RTC_PRESCALER_DIV32_gc);//fire it up, prescale by 32.
//*/
#else // It's a type b timer - we have already errored out if that wasn't defined
_timer->CCMP = TIME_TRACKING_TIMER_PERIOD;
// Enable timer interrupt, but clear the rest of register
Expand All @@ -1814,22 +1822,17 @@ void set_millis(__attribute__((unused))uint32_t newmillis)
#if defined(MILLIS_USE_TIMERNONE)
badCall("set_millis() is only valid with millis timekeeping enabled.");
#else
/*

#if defined(MILLIS_USE_TIMERRTC)
// timer_overflow_count = newmillis >> 16;
// millis = 61/64(timer_overflow_count << 16 + RTC.CNT)
// millis = 1000/1024*(timer_overflow_count << 16 + RTC.CNT)
uint8_t oldSREG = SREG; // save SREG
cli(); // interrupts off
uint16_t temp = (newmillis % 61) << 6;
newmillis = (newmillis / 61) << 6;
temp = temp / 61;
newmillis += temp;
timer_overflow_count = newmillis >> 16;
newmillis = ((newmillis/125)<<7) + (((newmillis%125)<<7)+62)/125; // *1024/1000
cli(); // interrupts off
timingStruct.timer_overflow_count = newmillis >> 16;
while(RTC.STATUS&RTC_CNTBUSY_bm); // wait if RTC busy
RTC.CNT = newmillis & 0xFFFF;
SREG = oldSREG; // reemable oimterripts if we killed them,
SREG = oldSREG; // reenable interrupts if we killed them,
#else
*/
/* farting around with micros via overflow count was ugly and buggy.
* may implement again, better, in the future - but millis and micros
* will get out of sync when you use set_millis
Expand All @@ -1855,7 +1858,7 @@ void set_millis(__attribute__((unused))uint32_t newmillis)
* -SK 2/4/23
*/
timingStruct.timer_millis = newmillis;
//#endif
#endif
#endif
}

Expand Down