"linnix" <me@linnix.info-for.us> wrote in message news:1157036811.432184.292510@b28g2000cwb.googlegroups.com...> > Al wrote: >> In article <1156979843.522090.281930@h48g2000cwc.googlegroups.com>, >> "linnix" <me@linnix.info-for.us> wrote: >> >> > Al wrote: >> > > In article <1156882054.604376.170200@m79g2000cwm.googlegroups.com>, >> > > "linnix" <me@linnix.info-for.us> wrote: >> > > >> > > > > > Is this an appropriate newsgroup to submit questions regarding >> > > > > > PICs? >> > > > > > >> > > > > > I haven't been able to find any newsgroups listed as such that >> > > > > > are >> > > > > > provided by my ISP. >> > > > > > >> > > > > > Al >> > > > > >> > > > > Definitely. This is the place. >> > > > >> > > > Only if you are willing to ask the same question in an auditorium >> > > > full >> > > > of 500 experienced engineers. >> > > > >> > > >> > > OK, thanks. I'm overwhelmed by the response. >> > > >> > > First question. >> > > >> > > I want to use a real time clock for my application. I want to make >> > > the >> > > thing as cheaply as possible so I am looking for the lowlyest (??) >> > > PIC I >> > > can use. I have my sights set on the 12C508A. >> > > >> > > What I want to do is use two pins for the RT clock, two for >> > > controlling >> > > an external device, and two for communicating with the PIC from an >> > > external terminal service, yet to be determined. >> > > >> > > I know I may not have enough program space to do this, but I'm just >> > > starting. >> > > >> > > At any rate, what I want to know is this. A real time clock chip like >> > > the NJU6355 has three pins, CE, a clock and a data I/O. Can I do a >> > > hardware CE and still have full functionality of the RT clock using >> > > just >> > > the clock and I/O pins? >> > >> > What would your hardware CE be? It must determine the I/O direction >> > for the PIC to handle it properly. By the way, why can't you implement >> > the RTC inside the PIC? >> > >> > > >> > > As you can see, I run out of PIC pins if I can't. >> > > >> > > Al >> > >> >> According to the spec for the RTC, CE HIGH means that I/O is available >> and nothing else. So, as I think about it more, I think that I can just >> set it HIGH and as long as I am not querying the RTC, I should be >> getting nothing out. And if I ask for the day of the week, I should get >> that data out. > > I could be wrong, but CE determine the direction of the DATA pin. > Forgive me if I read the spec incorrectly. > >> >> I'm not attempting to do RTC inside the PIC as I want to use the >> cheapest one available, like the 12C508A. And why reinvent the wheel. > > There are plenty of software library to implement a clock in PIC, which > would cut the cost (and the RTC chip). You don't have to reinvent it. > >> >> Al >The CE input is CHIP ENABLE, NOT Direction! Don
Charter of newsgroup
Started by ●August 29, 2006
Reply by ●August 31, 20062006-08-31
Reply by ●August 31, 20062006-08-31
Donald Harris wrote:> "linnix" <me@linnix.info-for.us> wrote in message > news:1157036811.432184.292510@b28g2000cwb.googlegroups.com... > > > > Al wrote: > >> In article <1156979843.522090.281930@h48g2000cwc.googlegroups.com>, > >> "linnix" <me@linnix.info-for.us> wrote: > >> > >> > Al wrote: > >> > > In article <1156882054.604376.170200@m79g2000cwm.googlegroups.com>, > >> > > "linnix" <me@linnix.info-for.us> wrote: > >> > > > >> > > > > > Is this an appropriate newsgroup to submit questions regarding > >> > > > > > PICs? > >> > > > > > > >> > > > > > I haven't been able to find any newsgroups listed as such that > >> > > > > > are > >> > > > > > provided by my ISP. > >> > > > > > > >> > > > > > Al > >> > > > > > >> > > > > Definitely. This is the place. > >> > > > > >> > > > Only if you are willing to ask the same question in an auditorium > >> > > > full > >> > > > of 500 experienced engineers. > >> > > > > >> > > > >> > > OK, thanks. I'm overwhelmed by the response. > >> > > > >> > > First question. > >> > > > >> > > I want to use a real time clock for my application. I want to make > >> > > the > >> > > thing as cheaply as possible so I am looking for the lowlyest (??) > >> > > PIC I > >> > > can use. I have my sights set on the 12C508A. > >> > > > >> > > What I want to do is use two pins for the RT clock, two for > >> > > controlling > >> > > an external device, and two for communicating with the PIC from an > >> > > external terminal service, yet to be determined. > >> > > > >> > > I know I may not have enough program space to do this, but I'm just > >> > > starting. > >> > > > >> > > At any rate, what I want to know is this. A real time clock chip like > >> > > the NJU6355 has three pins, CE, a clock and a data I/O. Can I do a > >> > > hardware CE and still have full functionality of the RT clock using > >> > > just > >> > > the clock and I/O pins? > >> > > >> > What would your hardware CE be? It must determine the I/O direction > >> > for the PIC to handle it properly. By the way, why can't you implement > >> > the RTC inside the PIC? > >> > > >> > > > >> > > As you can see, I run out of PIC pins if I can't. > >> > > > >> > > Al > >> > > >> > >> According to the spec for the RTC, CE HIGH means that I/O is available > >> and nothing else. So, as I think about it more, I think that I can just > >> set it HIGH and as long as I am not querying the RTC, I should be > >> getting nothing out. And if I ask for the day of the week, I should get > >> that data out. > > > > I could be wrong, but CE determine the direction of the DATA pin. > > Forgive me if I read the spec incorrectly. > > > >> > >> I'm not attempting to do RTC inside the PIC as I want to use the > >> cheapest one available, like the 12C508A. And why reinvent the wheel. > > > > There are plenty of software library to implement a clock in PIC, which > > would cut the cost (and the RTC chip). You don't have to reinvent it. > > > >> > >> Al > > > > The CE input is CHIP ENABLE, NOT Direction!Oh, yes. I read the wrong table. It should be Ok to pull it high.> > Don
Reply by ●August 31, 20062006-08-31
linnix wrote:> Donald Harris wrote: >... snip ...>> >> The CE input is CHIP ENABLE, NOT Direction! > > Oh, yes. I read the wrong table. It should be Ok to pull it high.The time has come for you to learn to snip irrelevant material in your quotations. See especially the last link below. -- Some informative links: news:news.announce.newusers http://www.geocities.com/nnqweb/ http://www.catb.org/~esr/faqs/smart-questions.html http://www.caliburn.nl/topposting.html http://www.netmeister.org/news/learn2quote.html
Reply by ●August 31, 20062006-08-31
In article <3_DJg.9177$4O4.6831@trnddc02>, "Donald Harris" <harrisdw1@verizon.net> wrote: <big snip>> > > >> > >> I'm not attempting to do RTC inside the PIC as I want to use the > >> cheapest one available, like the 12C508A. And why reinvent the wheel. > > > > There are plenty of software library to implement a clock in PIC, which > > would cut the cost (and the RTC chip). You don't have to reinvent it. > > > >> > >> Al > >OK, I'll look for a library. Will it fit in the half K program section of the 12C508A as well as the other functionality I need? More analysis to do. Al
Reply by ●August 31, 20062006-08-31
Al wrote:> In article <3_DJg.9177$4O4.6831@trnddc02>, > "Donald Harris" <harrisdw1@verizon.net> wrote: > > <big snip> > > > > > > > >> > > >> I'm not attempting to do RTC inside the PIC as I want to use the > > >> cheapest one available, like the 12C508A. And why reinvent the wheel. > > > > > > There are plenty of software library to implement a clock in PIC, which > > > would cut the cost (and the RTC chip). You don't have to reinvent it. > > > > > >> > > >> Al > > > > > OK, I'll look for a library. Will it fit in the half K program section > of the 12C508A as well as the other functionality I need? More analysis > to do. >Here is the core function, should compile to less than couple hundred bytes: gSECOND++; // increment second if (gSECOND == 60) { gSECOND = 0; gMINUTE++; if (gMINUTE > 59) { gMINUTE = 0; gHOUR++; if (gHOUR > 23) { gHOUR = 0; gDAY++; // Check for leap year if month == February if (gMONTH == 2) if (!(gYEAR & 0x0003)) // if (gYEAR%4 == 0) if (gYEAR%100 == 0) if (gYEAR%400 == 0) LeapMonth = 1; else LeapMonth = 0; else LeapMonth = 1; else LeapMonth = 0; else LeapMonth = 0; // Now, we can check for month length if (gDAY > (MonthLength[gMONTH] + LeapMonth)) { gDAY = 1; gMONTH++; if (gMONTH > 12) { gMONTH = 1; gYEAR++; } } } }> Al
Reply by ●September 1, 20062006-09-01
In article <1157057976.567050.172630@b28g2000cwb.googlegroups.com>, "linnix" <me@linnix.info-for.us> wrote:> Al wrote: > > In article <3_DJg.9177$4O4.6831@trnddc02>, > > "Donald Harris" <harrisdw1@verizon.net> wrote: > > > > <big snip> > > > > > > > > > > > >> > > > >> I'm not attempting to do RTC inside the PIC as I want to use the > > > >> cheapest one available, like the 12C508A. And why reinvent the wheel. > > > > > > > > There are plenty of software library to implement a clock in PIC, which > > > > would cut the cost (and the RTC chip). You don't have to reinvent it. > > > > > > > >> > > > >> Al > > > > > > > > OK, I'll look for a library. Will it fit in the half K program section > > of the 12C508A as well as the other functionality I need? More analysis > > to do. > > > > Here is the core function, should compile to less than couple hundred > bytes: > > gSECOND++; // increment second > > if (gSECOND == 60) > { > gSECOND = 0; > gMINUTE++; > > if (gMINUTE > 59) > { > gMINUTE = 0; > gHOUR++; > > if (gHOUR > 23) > { > gHOUR = 0; > gDAY++; > > // Check for leap year if month == February > if (gMONTH == 2) > if (!(gYEAR & 0x0003)) // if (gYEAR%4 > == 0) > if (gYEAR%100 == 0) > if (gYEAR%400 == 0) > LeapMonth = 1; > else > LeapMonth = 0; > else > LeapMonth = 1; > else > LeapMonth = 0; > else > LeapMonth = 0; > > // Now, we can check for month length > if (gDAY > (MonthLength[gMONTH] + LeapMonth)) > { > gDAY = 1; > gMONTH++; > > if (gMONTH > 12) > { > gMONTH = 1; > gYEAR++; > } > } > } > } > > > Al >OK, looks good. I'll compile just this segment and see how much space it takes. I'll post the results here. Thanks for the tip. Now since I will be using the internal RC clock of the the 12C508A, how significantly will this impact the accuracy of the clock? I know that temperature effects will be important. If the code above works out with the space I have and the other functionality, I can use an exteranl XTAL for timing rather than use the two pins for connection to an external RTC. If I can eliminate the XTAL, that would be even better. BTW, this is a pro bono job for an application in the third world, so thanks again. It makes it a little easier for me. I am trying to keep the cost down to less than $5US/unit. I can't divulge the project, but you can guess that time in involved. Al
Reply by ●September 1, 20062006-09-01
In article <no.spam-A6551E.09275101092006@news.verizon.net>, Al <no.spam@wanted.com> wrote:> In article <1157057976.567050.172630@b28g2000cwb.googlegroups.com>, > "linnix" <me@linnix.info-for.us> wrote: ><big snip>> > OK, looks good. I'll compile just this segment and see how much space it > takes. I'll post the results here. >Here is the result for the RTC code you provided. It may just work out. ROM used: 159 (31%) 159 (31%) including unused fragments 1 Average locations per line 5 Average locations per statement RAM used: 14 (56%) at main() level 17 (68%) worst case Lines Stmts % Files ----- ----- --- ----- 69 31 100 C:\My Documents\Projects\Test\RTC.c 93 0 0 C:\Program Files\PICC\devices\12C508A.h ----- ----- 324 62 Total Page ROM % RAM Functions: ---- --- --- --- ---------- 0 100 63 9 main 0 21 13 3 @DIV88 0 38 24 5 @DIV1616 Segment Used Free --------- ---- ---- 00000-001FF 159 349 Al
Reply by ●September 1, 20062006-09-01
Al wrote:> In article <1157057976.567050.172630@b28g2000cwb.googlegroups.com>, > "linnix" <me@linnix.info-for.us> wrote: > > > Al wrote: > > > In article <3_DJg.9177$4O4.6831@trnddc02>, > > > "Donald Harris" <harrisdw1@verizon.net> wrote: > > > > > > <big snip> > > > > > > > > > > > > > > > >> > > > > >> I'm not attempting to do RTC inside the PIC as I want to use the > > > > >> cheapest one available, like the 12C508A. And why reinvent the wheel. > > > > > > > > > > There are plenty of software library to implement a clock in PIC, which > > > > > would cut the cost (and the RTC chip). You don't have to reinvent it. > > > > > > > > > >> > > > > >> Al > > > > > > > > > > > OK, I'll look for a library. Will it fit in the half K program section > > > of the 12C508A as well as the other functionality I need? More analysis > > > to do. > > > > > > > Here is the core function, should compile to less than couple hundred > > bytes: > > > > gSECOND++; // increment second > > > > if (gSECOND == 60) > > { > > gSECOND = 0; > > gMINUTE++; > > > > if (gMINUTE > 59) > > { > > gMINUTE = 0; > > gHOUR++; > > > > if (gHOUR > 23) > > { > > gHOUR = 0; > > gDAY++; > > > > // Check for leap year if month == February > > if (gMONTH == 2) > > if (!(gYEAR & 0x0003)) // if (gYEAR%4 > > == 0) > > if (gYEAR%100 == 0) > > if (gYEAR%400 == 0) > > LeapMonth = 1; > > else > > LeapMonth = 0; > > else > > LeapMonth = 1; > > else > > LeapMonth = 0; > > else > > LeapMonth = 0; > > > > // Now, we can check for month length > > if (gDAY > (MonthLength[gMONTH] + LeapMonth)) > > { > > gDAY = 1; > > gMONTH++; > > > > if (gMONTH > 12) > > { > > gMONTH = 1; > > gYEAR++; > > } > > } > > } > > } > > > > > Al > > > > OK, looks good. I'll compile just this segment and see how much space it > takes. I'll post the results here. > > Thanks for the tip. > > Now since I will be using the internal RC clock of the the 12C508A, how > significantly will this impact the accuracy of the clock? I know that > temperature effects will be important. If the code above works out with > the space I have and the other functionality, I can use an exteranl XTAL > for timing rather than use the two pins for connection to an external > RTC. If I can eliminate the XTAL, that would be even better.Use a watch crystal, it can't be more than 50 cents. Another way is to track the power line frequency (50 or 60 hz) and adjust your internal RC.> > BTW, this is a pro bono job for an application in the third world, so > thanks again. It makes it a little easier for me. I am trying to keep > the cost down to less than $5US/unit. I can't divulge the project, but > you can guess that time in involved.What else do you need? RTC and RS232 only?> > Al
