Hello everyone, I've got a bit of a strange problem with the RTC in my setup. I have a dedicated lithium battery going to the Vbat pin to power the RTC, and it usually works fine, however periodically the clock changes to an invalid value and stops running. Usually this value is something like "Year:129 Month:00 Day:16 Hour:02 Min:09 Sec:08", and unless I reset the RTC to a valid value it stops running. This will usually happen after several hours of Vcc absent (i.e. device powered off) or after a day or two running constantly. Nothing else is disrupted. I have a 3.6V lithium running through a diode which drops the voltage at the pin down to 3.165V when Vcc present and to 3.232V when Vcc absent (implying that more current is drawn when the micro is powered on??) Does anyone have any ideas? -- Sean
RTC problem in LPC2148
Started by ●January 30, 2006
Reply by ●January 30, 20062006-01-30
--- In lpc2000@lpc2..., Sean <embeddedrelated@w...> wrote: > > Hello everyone, > > I've got a bit of a strange problem with the RTC in my setup. I have a > dedicated lithium battery going to the Vbat pin to power the RTC, and it > usually works fine, however periodically the clock changes to an invalid > value and stops running. Usually this value is something like "Year:129 > Month:00 Day:16 Hour:02 Min:09 Sec:08", and unless I reset the RTC to a > valid value it stops running. This will usually happen after several hours > of Vcc absent (i.e. device powered off) or after a day or two running > constantly. Nothing else is disrupted. I have a 3.6V lithium running > through a diode which drops the voltage at the pin down to 3.165V when Vcc > present and to 3.232V when Vcc absent (implying that more current is drawn > when the micro is powered on??) > > Does anyone have any ideas? > > -- Sean I have had my setup working for a week already with a 3V lithium. I'm using a MMBD2838LT1 dual diode cathode connected. I have a 560ohm after the battery (which is probably not necessary) to one anode. Cathodes to the VBAT pin. Other anode to VDD so it is powering it when VDD is up. I haven't seen anything like what you are seeing. Also, I have a SE2417 separate crystal. Steve
Reply by ●January 31, 20062006-01-31
Sean wrote: >Hello everyone, > >I've got a bit of a strange problem with the RTC in my setup. I have a >dedicated lithium battery going to the Vbat pin to power the RTC, and it >usually works fine, however periodically the clock changes to an invalid >value and stops running. Usually this value is something like "Year:129 >Month:00 Day:16 Hour:02 Min:09 Sec:08", and unless I reset the RTC to a >valid value it stops running. This will usually happen after several hours >of Vcc absent (i.e. device powered off) or after a day or two running >constantly. Nothing else is disrupted. I have a 3.6V lithium running >through a diode which drops the voltage at the pin down to 3.165V when Vcc >present and to 3.232V when Vcc absent (implying that more current is drawn >when the micro is powered on??) > > > Diode switching is needed to maintain the Vbat when Vdd (3.3v main) is absent and to switch over to the battery when Vdd disappears. It sounds like you have that working? It will take two diodes (1N4148A) and a resistor (560ohm) to do this properly. Cathodes of both diodes go to Vbat line, anode of one diode goes to Vdd, anode of other diode is series with 560ohm to positive terminal of Lithium cell. This is half the solution, the hardware half. I found that my clock would also "explode" on occasion and seemingly at random. The solution I took was a bit more aggressive in the software. Study my clock routines, especially awakenClock() and sleepClock(). Essentially, when the clock registers are not needed, they are "disconnected". =============== begin RTCfuncs.c ==================/************************************************************* * RealTime awareness functions. Provide for elapsed time * intervals as well as reading data & time from RTC. * * (C) 2005 - Tom Walsh <tom@tom@...> * May be used for hobby or commercial purposes as long as * this notice remains intact. *************************************************************/ #include <LPC21xx.h> #include <lpcRTC.h> #include <time.h> #include <sys/times.h> #include <sysdefs.h> #include <system.h> #define CCR_CLKEN BIT(0) #define CCR_CTCRST BIT(1) #define CCR_CTTEST0 BIT(2) #define CCR_CTTEST1 BIT(3) #define CCR_CLKSRC BIT(4) #define T0_MS_DIV (PCLK / 10000) long systemTickCounter; static inline void sleepClock(void) {// place RTC on 32kHz xtal and disconnect power. RTCCCR = (CCR_CLKEN | CCR_CLKSRC); // power off the clock registers. PCONP &= ~PCRTC; } static inline void awakenClock(void) {// prepare clock for interactive use. RTCCCR = (CCR_CLKEN | CCR_CLKSRC); // power up the clock registers. PCONP |= PCRTC; } static void startMsTimer (void) {// tick timer, 1ms heartbeat for the system. // connect VIC to Timer0 Timer0VectAddr = (uint32_t)timer0ISR; // address of the ISR Timer0VectCntl = VIC_ENABLE | VIC_TIMER0; VICIntSelect &= ~VIC_BIT(VIC_TIMER0); // Timer0 selected as IRQ VICIntEnable = VIC_BIT(VIC_TIMER0); // Timer0 interrupt enabled T0TCR = TCR_RESET; // reset & disable timer 0 T0PC = 0; T0PR = T0_MS_DIV; T0CCR = 0; // timer mode. T0EMR = 0; // no external match. T0MR0 = 9; T0MCR = 3; // reset and interrupt on terminal count. T0TCR = TCR_ENABLE; // init the system ticks. systemTickCounter = 0; } void setElapsed (int HowLong, struct TIMER * timer, timertype_t TimerType) { /* set for a TimeElapsed event. */ timer->HowLong = HowLong; timer->Type = TimerType; if (timer->Type == TimerInMilli) timer->SetTime = times (0); else timer->SetTime = time (0); } bool timeElapsed (struct TIMER * timer) { /* return True if preset interval has expired. */ time_t TestTimerNow, TestTimeStart; if (timer->Type == TimerInMilli) TestTimerNow = times (0); else TestTimerNow = time (0); TestTimeStart = timer->SetTime; if (((TestTimeStart>TestTimerNow) ? (TestTimerNow + (~TestTimeStart)) : (TestTimerNow - TestTimeStart)) > timer->HowLong) { return True; } return False; } void initRTC(void) {// start clock so that the sytsem may use it. #ifdef HAS_CLOCK bool nonsense = False; rtcCTIME0_t ctime0; rtcCTIME1_t ctime1; rtcCTIME2_t ctime2; struct tm newTime; time_t resetTime; awakenClock(); // see if clock contains nonsense values. // grab time as consolidated to avoid misses. ctime0 = RTCCTIME0; ctime1 = RTCCTIME1; ctime2 = RTCCTIME2; // leisurely tear the packed time apart into individual time. if ((ctime0.seconds < 0) || (ctime0.seconds > 59)) nonsense = True; if ((ctime0.minutes < 0) || (ctime0.minutes > 59)) nonsense = True; if ((ctime0.hours < 0) || (ctime0.hours > 23)) nonsense = True; if ((ctime1.dayOfMonth < 1) || (ctime1.dayOfMonth > 31)) nonsense True; if ((ctime1.month < 1) || (ctime1.month > 12)) nonsense = True; if ((ctime1.year < 1980) || (ctime1.year > 2050)) nonsense = True; if ((ctime0.dayOfWeek < 0) || (ctime0.dayOfWeek > 6)) nonsense = True; if ((ctime2.dayOfYear < 0) || (ctime2.dayOfYear > 366)) nonsense = True; sleepClock (); if (nonsense) { // set the clock to Jan 1, 2006 00:00:00 resetTime = 1136073600l; localtime_r (&resetTime, &newTime); newTime.tm_year += 1900; newTime.tm_mon += 1; newTime.tm_yday += 1; writeRTC (&newTime); } #endif // start realtime heartbeat (1ms period). startMsTimer(); } /************************************************** * * readRTC & writeRTC are supporting functions * for the newlib stubs. * **************************************************/ void readRTC (struct tm *theTime) {// read clock registers and return tm structure. #ifdef HAS_CLOCK rtcCTIME0_t ctime0; rtcCTIME1_t ctime1; rtcCTIME2_t ctime2; awakenClock(); // grab time as consolidated to avoid misses. ctime0 = RTCCTIME0; ctime1 = RTCCTIME1; ctime2 = RTCCTIME2; // leisurely tear the packed time apart into individual time. theTime->tm_sec = ctime0.seconds; theTime->tm_min = ctime0.minutes; theTime->tm_hour = ctime0.hours; theTime->tm_mday = ctime1.dayOfMonth; theTime->tm_mon = ctime1.month; theTime->tm_year = ctime1.year; theTime->tm_wday = ctime0.dayOfWeek; theTime->tm_yday = ctime2.dayOfYear; theTime->tm_isdst = False; sleepClock (); #endif } void writeRTC (struct tm *newTime) {// set clock to new values. #ifdef HAS_CLOCK awakenClock(); // grab time as consolidated to avoid misses. RTCTCR->seconds = newTime->tm_sec; RTCTCR->minutes = newTime->tm_min; RTCTCR->hours = newTime->tm_hour; RTCTCR->dayOfMonth = newTime->tm_mday; RTCTCR->month = newTime->tm_mon; RTCTCR->year = newTime->tm_year; RTCTCR->dayOfWeek = newTime->tm_wday; RTCTCR->dayOfYear = newTime->tm_yday; sleepClock (); #endif } ================== snip ======================= The above functions are designed to work with the newlib gettimeofday(), settimeofday(), localtime(), etc.. My clock has been running for several months without failure. It has lost about 5 minutes, so I need to tweak the crystal capacitance... What also may be of note is how I setup my power control during system initialization: PCONP = ((PCTIM0 | PCTIM1 | PCUART0 | PCUART1 | PCRTC | PCSPI1 | PCAD0) & ~PCONP_MASK); Hope this helps, TomW -- Tom Walsh - WN3L - Embedded Systems Consultant http://openhardware.net, http://cyberiansoftware.com "Windows? No thanks, I have work to do..." ----------------
Reply by ●January 31, 20062006-01-31
Tom:
Thanks for the code!
Is it *necessary* to have the switching in place (as opposed to use leaving
the lithium to power the RTC all the time)? Just curious.
Instead of using the batt->res->diode what if I used a FET instead to
provide switching between Vcc and Vbat? This would also extend the battery
life (since it's also powering external SRAM as well). From Digikey a FET
is the same price as a single diode, so that would actually be cheaper (?)
-- Sean
At 22:24 1/30/2006, you wrote:
>Sean wrote:
>
> >Hello everyone,
> >
> >I've got a bit of a strange problem with the RTC in my setup. I
have a
> >dedicated lithium battery going to the Vbat pin to power the RTC, and
it
> >usually works fine, however periodically the clock changes to an
invalid
> >value and stops running. Usually this value is something like
"Year:129
> >Month:00 Day:16 Hour:02 Min:09 Sec:08", and unless I reset the RTC
to a
> >valid value it stops running. This will usually happen after several
hours
> >of Vcc absent (i.e. device powered off) or after a day or two running
> >constantly. Nothing else is disrupted. I have a 3.6V lithium running
> >through a diode which drops the voltage at the pin down to 3.165V when
Vcc
> >present and to 3.232V when Vcc absent (implying that more current is
drawn
> >when the micro is powered on??)
>
>Diode switching is needed to maintain the Vbat when Vdd (3.3v main) is
>absent and to switch over to the battery when Vdd disappears. It sounds
>like you have that working? It will take two diodes (1N4148A) and a
>resistor (560ohm) to do this properly. Cathodes of both diodes go to
>Vbat line, anode of one diode goes to Vdd, anode of other diode is
>series with 560ohm to positive terminal of Lithium cell.
>
>This is half the solution, the hardware half. I found that my clock
>would also "explode" on occasion and seemingly at random. The
solution
>I took was a bit more aggressive in the software. Study my clock
>routines, especially awakenClock() and sleepClock(). Essentially, when
>the clock registers are not needed, they are "disconnected".
Reply by ●January 31, 20062006-01-31
Use a BAT54C. Inside this component you have the 2 diodes (schotky ones
that have only 0,3V dropout) with their cathodes connected.
Sean wrote:
> Tom:
>
> Thanks for the code!
>
> Is it *necessary* to have the switching in place (as opposed to use
> leaving
> the lithium to power the RTC all the time)? Just curious.
>
> Instead of using the batt->res->diode what if I used a FET instead to
> provide switching between Vcc and Vbat? This would also extend the
> battery
> life (since it's also powering external SRAM as well). From Digikey a
> FET
> is the same price as a single diode, so that would actually be cheaper (?)
>
> -- Sean
>
> At 22:24 1/30/2006, you wrote:
> >Sean wrote:
> >
> > >Hello everyone,
> > >
> > >I've got a bit of a strange problem with the RTC in my setup.
I have a
> > >dedicated lithium battery going to the Vbat pin to power the RTC,
> and it
> > >usually works fine, however periodically the clock changes to an
> invalid
> > >value and stops running. Usually this value is something like
> "Year:129
> > >Month:00 Day:16 Hour:02 Min:09 Sec:08", and unless I reset
the RTC to a
> > >valid value it stops running. This will usually happen after
> several hours
> > >of Vcc absent (i.e. device powered off) or after a day or two
running
> > >constantly. Nothing else is disrupted. I have a 3.6V lithium
running
> > >through a diode which drops the voltage at the pin down to 3.165V
> when Vcc
> > >present and to 3.232V when Vcc absent (implying that more current
> is drawn
> > >when the micro is powered on??)
> >
> >Diode switching is needed to maintain the Vbat when Vdd (3.3v main) is
> >absent and to switch over to the battery when Vdd disappears. It
sounds
> >like you have that working? It will take two diodes (1N4148A) and a
> >resistor (560ohm) to do this properly. Cathodes of both diodes go to
> >Vbat line, anode of one diode goes to Vdd, anode of other diode is
> >series with 560ohm to positive terminal of Lithium cell.
> >
> >This is half the solution, the hardware half. I found that my clock
> >would also "explode" on occasion and seemingly at random.
The solution
> >I took was a bit more aggressive in the software. Study my clock
> >routines, especially awakenClock() and sleepClock(). Essentially, when
> >the clock registers are not needed, they are "disconnected".
>
>
>
> >.
>
>
>
>
Reply by ●January 31, 20062006-01-31
The BAT54C's that I see ($0.12 qty 100) all have horrible forward
voltage
drops (some are as bad as 1V at 50mA current!) and I'll still need to drop
the voltage further with a resistor, which drops the efficiency even
further. This device can also run off of a battery for main power, and
this circuit needs to power SRAM, so the peak will be around 50mA.
Do you know of any BAT54C's that have a much lower voltage drop? I see
Philips has BAT54CW which is 420mV at 50mA current, that's the best I can
find (yes, these are schottky).
The FET is the same price but will give me 0.2V drop without needing the
extra resistor, and because this disconnects the lithium there is no drop
at all when on main power. Is there any reason this wouldn't work?
-- Sean
At 00:17 1/31/2006, you wrote:
>Use a BAT54C. Inside this component you have the 2 diodes (schotky ones
>that have only 0,3V dropout) with their cathodes connected.
>
>
>
>
>Sean wrote:
> > Tom:
> >
> > Thanks for the code!
> >
> > Is it *necessary* to have the switching in place (as opposed to use
> > leaving
> > the lithium to power the RTC all the time)? Just curious.
> >
> > Instead of using the batt->res->diode what if I used a FET
instead to
> > provide switching between Vcc and Vbat? This would also extend the
> > battery
> > life (since it's also powering external SRAM as well). From
Digikey a
> > FET
> > is the same price as a single diode, so that would actually be cheaper
(?)
> >
> > -- Sean
> >
> > At 22:24 1/30/2006, you wrote:
> > >Sean wrote:
> > >
> > > >Hello everyone,
> > > >
> > > >I've got a bit of a strange problem with the RTC in my
setup. I have a
> > > >dedicated lithium battery going to the Vbat pin to power the
RTC,
> > and it
> > > >usually works fine, however periodically the clock changes to
an
> > invalid
> > > >value and stops running. Usually this value is something
like
> > "Year:129
> > > >Month:00 Day:16 Hour:02 Min:09 Sec:08", and unless I
reset the RTC to a
> > > >valid value it stops running. This will usually happen after
> > several hours
> > > >of Vcc absent (i.e. device powered off) or after a day or two
running
> > > >constantly. Nothing else is disrupted. I have a 3.6V
lithium running
> > > >through a diode which drops the voltage at the pin down to
3.165V
> > when Vcc
> > > >present and to 3.232V when Vcc absent (implying that more
current
> > is drawn
> > > >when the micro is powered on??)
> > >
> > >Diode switching is needed to maintain the Vbat when Vdd (3.3v
main) is
> > >absent and to switch over to the battery when Vdd disappears. It
sounds
> > >like you have that working? It will take two diodes (1N4148A) and
a
> > >resistor (560ohm) to do this properly. Cathodes of both diodes go
to
> > >Vbat line, anode of one diode goes to Vdd, anode of other diode is
> > >series with 560ohm to positive terminal of Lithium cell.
> > >
> > >This is half the solution, the hardware half. I found that my
clock
> > >would also "explode" on occasion and seemingly at
random. The solution
> > >I took was a bit more aggressive in the software. Study my clock
> > >routines, especially awakenClock() and sleepClock(). Essentially,
when
> > >the clock registers are not needed, they are
"disconnected".
Reply by ●January 31, 20062006-01-31
From the Philips Datasheet
Price : 0,08 / 100 pcs @ Digikey
240mV @ 0,1mA (that's far more than the RTC uses)
With do you need this resistor ? And even if you need it, let's see:
Using a 1K resistor, and a RTC current of 20uA gives you a dropout of
20mV ....
I use this a lot and I'm sure it works very well.
But I can't see how do you want to use a fet in this application.
Mauricio
Sean wrote:
> The BAT54C's that I see ($0.12 qty 100) all
have horrible forward voltage
> drops (some are as bad as 1V at 50mA current!) and I'll still need to
> drop
> the voltage further with a resistor, which drops the efficiency even
> further. This device can also run off of a battery for main power, and
> this circuit needs to power SRAM, so the peak will be around 50mA.
>
> Do you know of any BAT54C's that have a much lower voltage drop? I
see
> Philips has BAT54CW which is 420mV at 50mA current, that's the best I
can
> find (yes, these are schottky).
>
> The FET is the same price but will give me 0.2V drop without needing the
> extra resistor, and because this disconnects the lithium there is no drop
> at all when on main power. Is there any reason this wouldn't work?
>
> -- Sean
>
> At 00:17 1/31/2006, you wrote:
> >Use a BAT54C. Inside this component you have the 2 diodes (schotky ones
> >that have only 0,3V dropout) with their cathodes connected.
> >
> >
> >
> >
> >Sean wrote:
> > > Tom:
> > >
> > > Thanks for the code!
> > >
> > > Is it *necessary* to have the switching in place (as opposed to
use
> > > leaving
> > > the lithium to power the RTC all the time)? Just curious.
> > >
> > > Instead of using the batt->res->diode what if I used a FET
instead to
> > > provide switching between Vcc and Vbat? This would also extend
the
> > > battery
> > > life (since it's also powering external SRAM as well). From
Digikey a
> > > FET
> > > is the same price as a single diode, so that would actually be
> cheaper (?)
> > >
> > > -- Sean
> > >
> > > At 22:24 1/30/2006, you wrote:
> > > >Sean wrote:
> > > >
> > > > >Hello everyone,
> > > > >
> > > > >I've got a bit of a strange problem with the RTC in
my setup.
> I have a
> > > > >dedicated lithium battery going to the Vbat pin to power
the RTC,
> > > and it
> > > > >usually works fine, however periodically the clock
changes to an
> > > invalid
> > > > >value and stops running. Usually this value is
something like
> > > "Year:129
> > > > >Month:00 Day:16 Hour:02 Min:09 Sec:08", and unless
I reset the
> RTC to a
> > > > >valid value it stops running. This will usually happen
after
> > > several hours
> > > > >of Vcc absent (i.e. device powered off) or after a day
or two
> running
> > > > >constantly. Nothing else is disrupted. I have a 3.6V
lithium
> running
> > > > >through a diode which drops the voltage at the pin down
to 3.165V
> > > when Vcc
> > > > >present and to 3.232V when Vcc absent (implying that
more current
> > > is drawn
> > > > >when the micro is powered on??)
> > > >
> > > >Diode switching is needed to maintain the Vbat when Vdd (3.3v
> main) is
> > > >absent and to switch over to the battery when Vdd disappears.
It
> sounds
> > > >like you have that working? It will take two diodes
(1N4148A) and a
> > > >resistor (560ohm) to do this properly. Cathodes of both
diodes go to
> > > >Vbat line, anode of one diode goes to Vdd, anode of other
diode is
> > > >series with 560ohm to positive terminal of Lithium cell.
> > > >
> > > >This is half the solution, the hardware half. I found that
my clock
> > > >would also "explode" on occasion and seemingly at
random. The
> solution
> > > >I took was a bit more aggressive in the software. Study my
clock
> > > >routines, especially awakenClock() and sleepClock().
> Essentially, when
> > > >the clock registers are not needed, they are
"disconnected".
>
>
>
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Reply by ●January 31, 20062006-01-31
Mauricio Scaff wrote: > From the Philips Datasheet > >Price : 0,08 / 100 pcs @ Digikey >240mV @ 0,1mA (that's far more than the RTC uses) > >With do you need this resistor ? And even if you need it, let's see: >Using a 1K resistor, and a RTC current of 20uA gives you a dropout of >20mV .... > >I use this a lot and I'm sure it works very well. > > > If you are doing a commercial design which has to under Underwriters Labratories testing, They require that you need the current limiting resistor in the event that the diode shorts the battery won't rupture due to excessive current. TomW -- Tom Walsh - WN3L - Embedded Systems Consultant http://openhardware.net, http://cyberiansoftware.com "Windows? No thanks, I have work to do..." ----------------
Reply by ●February 10, 20062006-02-10
Just as a follow up, in case someone runs into this problem:
The answer to my question is yes, apparently you need to have the Vcc
switching in place to run the RTCK off of Vcc when Vcc is present, and Vbat
when Vcc is not present. If Vbat is used to power the RTC when Vcc is
present then the clock will do some strange things.
-- Sean
At 22:51 1/30/2006, you wrote:
>Tom:
>
>Thanks for the code!
>
>Is it *necessary* to have the switching in place (as opposed to use leaving
>the lithium to power the RTC all the time)? Just curious.
>
>-- Sean
>
>At 22:24 1/30/2006, you wrote:
> >Sean wrote:
> >
> > >Hello everyone,
> > >
> > >I've got a bit of a strange problem with the RTC in my setup.
I have a
> > >dedicated lithium battery going to the Vbat pin to power the RTC,
and it
> > >usually works fine, however periodically the clock changes to an
invalid
> > >value and stops running. Usually this value is something like
"Year:129
> > >Month:00 Day:16 Hour:02 Min:09 Sec:08", and unless I reset
the RTC to a
> > >valid value it stops running. This will usually happen after
several
> hours
> > >of Vcc absent (i.e. device powered off) or after a day or two
running
> > >constantly. Nothing else is disrupted. I have a 3.6V lithium
running
> > >through a diode which drops the voltage at the pin down to 3.165V
when Vcc
> > >present and to 3.232V when Vcc absent (implying that more current
is drawn
> > >when the micro is powered on??)
> >
> >Diode switching is needed to maintain the Vbat when Vdd (3.3v main) is
> >absent and to switch over to the battery when Vdd disappears. It
sounds
> >like you have that working? It will take two diodes (1N4148A) and a
> >resistor (560ohm) to do this properly. Cathodes of both diodes go to
> >Vbat line, anode of one diode goes to Vdd, anode of other diode is
> >series with 560ohm to positive terminal of Lithium cell.
> >
> >This is half the solution, the hardware half. I found that my clock
> >would also "explode" on occasion and seemingly at random.
The solution
> >I took was a bit more aggressive in the software. Study my clock
> >routines, especially awakenClock() and sleepClock(). Essentially, when
> >the clock registers are not needed, they are "disconnected".
>
>
>
>----------
>>Yahoo! Terms of Service.
>
>
>----------
