Post by thread:[PIC]: PIC12f629 need help with timed sleep.

I want to put a 12f629 pic into low power sleep mode for aprox 16 seconds (not critical.) I know you can do it by using the watchdog oscilator, but this newbie has absolutely no idea how to do it. I have scoured the archive but can't seem to find any resource that can help me. can someone please point me in the right direction. thanks Pk. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email spam_OUTlistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

> I want to put a 12f629 pic into low power sleep mode for aprox 16 > seconds (not critical.) > > I know you can do it by using the watchdog oscilator, but this newbie > has absolutely no idea how to do it. You enter sleep mode with the SLEEP instruction. Various events can cause a wakeup from sleep, including the watchdog timer. However, watchdog timer causes a reset so would therefore not continue from the SLEEP instruction (unless they put in a special case for that. I've never done this, so check the manual). Also, 16 seconds is longer than a single watchdog timer timeout, so you will have to count multiple watchdog timeouts to get to approximately 16 seconds. ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email .....listservKILLspam@spam@mitvma.mit.edu with SET PICList DIGEST in the body

On Fri, 7 Mar 2003, Paul Kennedy wrote: > I want to put a 12f629 pic into low power sleep mode for aprox 16 seconds > (not critical.) If it's really, really not critical (like if plus or minus a second or two is OK), just use six or seven SLEEP instructions with the watchdog configured for 2.3 seconds. A 32kHz xtal on timer1 will work for much more precise timing. Dale -- It's a thankless job, but I've got a lot of Karma to burn off. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

On Thu, 6 Mar 2003, Olin Lathrop wrote: > You enter sleep mode with the SLEEP instruction. Various events can cause > a wakeup from sleep, including the watchdog timer. However, watchdog > timer causes a reset so would therefore not continue from the SLEEP > instruction (unless they put in a special case for that. I've never done > this, so check the manual). WDT wakeup from SLEEP is viewed as the resumption of normal operation. During SLEEP it's called WDT wake-up, when not in SLEEP mode it's called WDT Reset. This applies to all 12/16x parts I have tried, not just the 12F629 and is documented in the data sheets and the PIC Midrange manual. Dale -- It's a thankless job, but I've got a lot of Karma to burn off. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email .....listservKILLspam.....mitvma.mit.edu with SET PICList DIGEST in the body

At 01:49 PM 3/6/2003 -0600, you wrote: >On Fri, 7 Mar 2003, Paul Kennedy wrote: > > > I want to put a 12f629 pic into low power sleep mode for aprox 16 seconds > > (not critical.) > >If it's really, really not critical (like if plus or minus a second or two >is OK), just use six or seven SLEEP instructions with the watchdog >configured for 2.3 seconds. A 32kHz xtal on timer1 will work for much >more precise timing. The worst case variation (including temperature) is a lot greater than 1-2 seconds in 16. Each period can be as short as 7ms or as long as 33ms, without the prescaler. And that's not tested, but characterized, meaning that a certain percentage of chips will fall outside of that range. IOW if you did 7 * 128, you'd have a typical time of 16.1 seconds, but a minimum of 6.27 seconds and a maximum of 29.6 seconds. Best regards, Spehro Pefhany --"it's the network..." "The Journey is the reward" EraseMEspeffspam_OUTTakeThisOuTinterlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listservspam_OUTmitvma.mit.edu with SET PICList DIGEST in the body

> I know you can do it by using the watchdog oscillator, but this > newbie has absolutely no idea how to do it You'd need something like this, assuming a ~2.3 second WDT, ie maximum (128) pre-scaler movlw 0xf9 ;count up to 00 (7 WDT wake-ups) movwf count zzzz sleep ;power down incfsz count ;increment count on WDT wake-up goto zzzz ;not done, back to sleep more code ;resumes here after 16.1 seconds Don't forget to enable the WDT in CONFIG. If you use the pre- scaler, assign it to WDT in OPTION. The WDT has a nominal period of 18ms, and you could get closer to 16 seconds by using a pre-scaler of 8 and a 111 count (16000/18=888, 8* 111*0.018 = 15.984s), but this does use fractionally more power because of the greater number of wake-ups and WDT is temperature-sensitive anyway Note that the instruction after the SLEEP is pre-loaded at the time the SLEEP is executed, and has immediate priority on wake-up, ahead of any IRQs. If you have a wake-up source (eg pin interrupt) that you wish to be the program flow controller you should put an NOP after the SLEEP. This will cause the interrrupt jump to be performed on wake-up -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email @spam@listservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

> The worst case variation (including temperature) is a lot > greater than 1-2 seconds in 16. Each period can be as > short as 7ms or as long as 33ms, without the prescaler. > And that's not tested, but characterized,meaning that a > certain percentage of chips will fall outside of that range My experience with a few PICs has been that WDT is quite dependably 18ms at 25C. As you say though, temperature is a factor, approximately 0.1s / 5C. Not a good idea to rely on WDT for accurate timing unless tested in the actual chip used and/or the application can tolerate variations -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email KILLspamlistservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

> WDT wakeup from SLEEP is viewed as the resumption of > normal operation. During SLEEP it's called WDT wake-up, > when not in SLEEP mode it's called WDT Reset Paul, one important thing about using WDT. It can be turned on/off only through CONFIG, meaning when you aren't using it for the SLEEP wake-up function, you'll have to dot a few CLRWDT instructions through your code to stop it resetting the PIC. That would be another advantage to using the max pre-scaler, as a CLRWDT needs to be executed only every 2.3s, which should be fairly easy to do -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email RemoveMElistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

> -----Original Message----- > From: Jinx [SMTP:spamBeGonejoecolquittspamBeGoneCLEAR.NET.NZ] > Sent: Thursday, March 06, 2003 9:23 PM > To: TakeThisOuTPICLISTEraseMEspam_OUTMITVMA.MIT.EDU > Subject: Re: [PIC]: PIC12f629 need help with timed sleep. > > > The worst case variation (including temperature) is a lot > > greater than 1-2 seconds in 16. Each period can be as > > short as 7ms or as long as 33ms, without the prescaler. > > And that's not tested, but characterized,meaning that a > > certain percentage of chips will fall outside of that range > > My experience with a few PICs has been that WDT is quite > dependably 18ms at 25C. As you say though, temperature > is a factor, approximately 0.1s / 5C. Not a good idea to rely > on WDT for accurate timing unless tested in the actual chip > used and/or the application can tolerate variations > I'm hoping that's 0.1ms? :o) Mike ======================================================================= This e-mail is intended for the person it is addressed to only. The information contained in it may be confidential and/or protected by law. If you are not the intended recipient of this message, you must not make any use of this information, or copy or show it to any person. Please contact us immediately to tell us that you have received this e-mail, and return the original to us. Any use, forwarding, printing or copying of this message is strictly prohibited. No part of this message can be considered a request for goods or services. ======================================================================= Any questions about Bookham's E-Mail service should be directed to RemoveMEpostmasterTakeThisOuTbookham.com. -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestEraseME.....mitvma.mit.edu>

> > My experience with a few PICs has been that WDT is quite > > dependably 18ms at 25C. As you say though, temperature > > is a factor, approximately 0.1s / 5C. Not a good idea to rely > > on WDT for accurate timing unless tested in the actual chip > > used and/or the application can tolerate variations > > > I'm hoping that's 0.1ms? :o) > > Mike Er...ummm..... I double-checked and get ~0.1ms / degC for an 18ms WDT period. I didn't factor in the pre-scaler or the 10C Check, just in case I made another blue WDT with /128 pre-scaler 2.2125s @ 20C 2.3324s @ 30C Diff = 0.1199s / 10C = 0.01199s / C /128 = 0.0000937 = 0.094ms / 18ms period / degC 'kay ? -- http://www.piclist.com hint: To leave the PICList EraseMEpiclist-unsubscribe-requestmitvma.mit.edu>

{Quote hidden}> > > My experience with a few PICs has been that WDT is quite > > > dependably 18ms at 25C. As you say though, temperature > > > is a factor, approximately 0.1s / 5C. Not a good idea to rely on > > > WDT for accurate timing unless tested in the actual chip used > > > and/or the application can tolerate variations > > > > > I'm hoping that's 0.1ms? :o) > > > > Mike > > Er...ummm..... I double-checked and get ~0.1ms / degC for an > 18ms WDT period. I didn't factor in the pre-scaler or the 10C > > Check, just in case I made another blue > > WDT with /128 pre-scaler > > 2.2125s @ 20C > 2.3324s @ 30C > > Diff = 0.1199s / 10C = 0.01199s / C > > /128 = 0.0000937 = 0.094ms / 18ms period / degC > > 'kay ? Sounds right to me too. In a project with WDT configured as above and TMR1 running a 32kHz crystal to produce a wake-up from sleep every 2 seconds I observed my PIC waking up earlier than expected when cooled in a refrigerator. The watchdog timer period had dropped to something less than 2 seconds and consequently caused a wake from sleep just before TMR1 was due to cause the wake up. -- Brent Brown, Electronic Design Solutions 16 English Street, Hamilton, New Zealand Ph/fax: +64 7 849 0069 Mobile/txt: 025 334 069 eMail: RemoveMEbrent.brownEraseMEEraseMEclear.net.nz -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestspam_OUTKILLspammitvma.mit.edu>

thanks Jinx this did the job perfectly. ----- Original Message ----- From: "Jinx" <RemoveMEjoecolquittTakeThisOuTspamCLEAR.NET.NZ> To: <EraseMEPICLISTspamspamBeGoneMITVMA.MIT.EDU> Sent: Friday, March 07, 2003 10:09 AM Subject: Re: [PIC]: PIC12f629 need help with timed sleep. {Quote hidden}> > I know you can do it by using the watchdog oscillator, but this > > newbie has absolutely no idea how to do it > > You'd need something like this, assuming a ~2.3 second WDT, > ie maximum (128) pre-scaler > > movlw 0xf9 ;count up to 00 (7 WDT wake-ups) > movwf count > > zzzz sleep ;power down > incfsz count ;increment count on WDT wake-up > goto zzzz ;not done, back to sleep > > more code ;resumes here after 16.1 seconds > > Don't forget to enable the WDT in CONFIG. If you use the pre- > scaler, assign it to WDT in OPTION. The WDT has a nominal > period of 18ms, and you could get closer to 16 seconds by > using a pre-scaler of 8 and a 111 count (16000/18=888, 8* > 111*0.018 = 15.984s), but this does use fractionally more > power because of the greater number of wake-ups and WDT > is temperature-sensitive anyway > > Note that the instruction after the SLEEP is pre-loaded at the > time the SLEEP is executed, and has immediate priority on > wake-up, ahead of any IRQs. If you have a wake-up source (eg > pin interrupt) that you wish to be the program flow controller you > should put an NOP after the SLEEP. This will cause the interrrupt > jump to be performed on wake-up > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email RemoveMElistservKILLspammitvma.mit.edu with SET PICList DIGEST in the body > -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

> I find it interesting that I look to a global mail list for help and > someone from my own town answers my question. :o) ...next time you set GIE make sure the Hamilton flag is disabled? Happy PIC'ing! -- Brent Brown, Electronic Design Solutions 16 English Street, Hamilton, New Zealand Ph/fax: +64 7 849 0069 Mobile/txt: 025 334 069 eMail: brent.brownSTOPspamspam_OUTclear.net.nz -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics