RTC Clock - Resetting

[gavo]

Hi,

I am battling with a RTC Clock that keeps re-setting after I loose power. I have done a few things which has helped the RTC keep the time when the power is off.

Please see code below:

* When I program the PIC I first need to exclude this line of code:

Shiftout IO, SCLK, LSBFIRST, [$8e, 128]

* and then I Re-insert the line of code after I program the PIC for the first time then the RTC Clock runs if power is disconnected

* I have also deleted the GoSub Gettime Routine after I also program the PIC for the First time that also seems to help as well

Is there any other way of doing this without deleting the above?

Any help would be greatly appreciated..;-)


' This will not affect normal program operation.
Define LOADER_USED 1
define OSC 20
Include "MODEDEFS.BAS" ' Include Shiftin/out modes
Define LCD_DREG PORTD ' Define LCD connections
Define LCD_DBIT 0
Define LCD_RSREG PORTA
Define LCD_RSBIT 0
Define LCD_EREG PORTA
Define LCD_EBIT 1

' Alias pins

RST Var PORTC.2
IO Var PORTC.1
SCLK Var PORTC.0

' Allocate variables

rtcyear Var byte
rtcday Var byte
rtcmonth Var byte
rtcdate Var byte
rtchr Var byte
rtcmin Var byte
rtcsec Var byte
rtccontrol Var byte

Low RST ' Reset RTC

Low SCLK

ADCON1 = 7 ' PORTA and E digital

'Shiftout IO, SCLK, LSBFIRST, [$8e, 0]

rtcyear = $14
rtcday = $04
rtcmonth = $7
rtcdate = $24
rtchr = $07
rtcmin = $57
rtcsec = $00


Gosub settime ' Set the time

Goto mainloop ' Skip subroutines

' Subroutine to write time to RTC

settime:

RST = 1 ' Ready for transfer

Shiftout IO, SCLK, LSBFIRST, [$8e, 0] ' Enable write

RST = 0 ' Reset RTC

RST = 1 ' Ready for transfer

' Write all 8 RTC registers in burst mode
Shiftout IO, SCLK, LSBFIRST, [$8e, 128]
Shiftout IO, SCLK, LSBFIRST, [$be, rtcsec, rtcmin, rtchr, rtcdate, rtcmonth, rtcday, rtcyear, 0]

RST = 0 ' Reset RTC
'Shiftout IO, SCLK, LSBFIRST, [$8e, 128]

Return



gettime:

RST = 1 ' Ready for transfer

Shiftout IO, SCLK, LSBFIRST, [$bf] ' Read all 8 RTC registers in burst mode

Shiftin IO, SCLK, LSBPRE, [rtcsec, rtcmin, rtchr, rtcdate, rtcmonth, rtcday, rtcyear, rtccontrol]

RST = 0 ' Reset RTC

Return

' Main program loop - in this case, it only updates the LCD with the time

mainloop:

Gosub gettime ' Read the time from the RTC

' Display time on LCD

Lcdout $fe, 1, hex2 rtcmonth, "/", hex2 rtcdate, "/" , hex2 rtcyear," "
Lcdout $fe,$C0, hex2 rtchr, ":", hex2 rtcmin, ":", hex2 rtcsec

Pause 30 ' Do it about 3 times a second

Goto mainloop


End

[richard]

some rtc's power on reset to a set value eg ds1307 power on default is 01/01/00 01 .
you can look for this value when your pic powers up and if its something else then assume the time is still set and leave it as it is.


extract from the ds1307 data sheet


On first application of power to the device the time and date registers are typically reset to 01/01/00 01 00:00:00 (MM/DD/YY DOW HH:MM:SS). The CH bit in the seconds register will be set to a 1.

[LinkMTech]

Are you using a battery backup on the RTC that is isolated from the rest of the power supply?

[gavo]

Hi Louie,

Yes I am connecting as per the datasheet, I am using a DS1302

Regards,

gavo

[gavo]

Hi Richard,

I seem to be doing everything correct, I even had MAXIM have a look at what I was doing, and they said it all looked good, that is why I am at such a loss having to program the device twice

Regards,

gavo

[richard]

the 1302 seems to have no defined por register settings, so why not write a couple of bytes to the rtc's ram when you set the time . on subsequent pic boot ups check the rtc ram for those bytes , if they are not set then run your settime code

[LinkMTech]

I noticed you have "rtccontrol Var byte" but no value assigned to it, then used in the "gettime" sub-routine.
What is supposed to happen there?

I would also suggest using a button input to jump to "settime" so you only have to program once and just push the button to set the time while its running.



' Main program loop - in this case, it only updates the LCD with the time

mainloop:

Gosub gettime ' Read the time from the RTC

' Display time on LCD

Lcdout $fe, 1, hex2 rtcmonth, "/", hex2 rtcdate, "/" , hex2 rtcyear," "
Lcdout $fe,$C0, hex2 rtchr, ":", hex2 rtcmin, ":", hex2 rtcsec

Pause 30 ' Do it about 3 times a second

IF !switch THEN GOSUB settime

Goto mainloop

End


And add a While/Wend for the switch so it waits before going back or else it'll be continuously setting the time until you release the button.



settime:

RST = 1 ' Ready for transfer

Shiftout IO, SCLK, LSBFIRST, [$8e, 0] ' Enable write

RST = 0 ' Reset RTC

RST = 1 ' Ready for transfer

' Write all 8 RTC registers in burst mode
Shiftout IO, SCLK, LSBFIRST, [$8e, 128]
Shiftout IO, SCLK, LSBFIRST, [$be, rtcsec, rtcmin, rtchr, rtcdate, rtcmonth, rtcday, rtcyear, 0]

RST = 0 ' Reset RTC
'Shiftout IO, SCLK, LSBFIRST, [$8e, 128]

WHILE !switch: WEND ' Wait until button is released

Return

[EarlyBird2]

When a RTC is installed with battery backup the time only needs setting once. There are no routines within your code to utilise the settime: and by including the line
Shiftout IO, SCLK, LSBFIRST, [$8e, 128] writes are disabled.

Could I suggest you have two programs one to set the initial time which includes the settime:, without Shiftout IO, SCLK, LSBFIRST, [$8e, 128] line and a second program that does not include settime:.

You are stuck with a two stage programing process but the second program will not include the unused settime: code.

There are other alternatives as others have suggested one would be to read the date from the RTC and compare to the initial settings. What are the readings from the RTC before any time is set? Is the default reading on power up 01/01/00 for example. If so then simply test for the year being 00 and if it is set the time else skip over it.

Let me know what the default power up readings are and then I can help with the code.

[gavo]

Hi Steve,

My apologies for the delay

Default Clock is:

01:01:00
00:00:80

Clock does not move

Regards,

Gavin

[EarlyBird2]

Gavin,

Gosub gettime before settime. Then if year =00 then settime also remove the disableing line "Shiftout IO, SCLK, LSBFIRST, [$8e, 128] "

[Ioannis]

Gavin, didn't we solve that issue?

Ioannis

[gavo]

Yes we did, I was seeing if I could do a "one time" programming instead of 2, the rest is working 100%

Regards,

Gavin

[EarlyBird2]

Yes we did, I was seeing if I could do a "one time" programming instead of 2, the rest is working 100%

Regards,

Gavin

Is the one time programing working?
Need more help?

[Ioannis]

Steve gave you the idea. Check the default of the DS1302 and then decide to setup or continue the normal program flow.

Ioannis