Ds 1302 rtc

Archiver

Hi,

I am endeavoring to keep time with a RTC DS 1302 but am having a bit of
trouble understanding how to do it. I have copied and pasted the program
that parallax uses as an example to accompany the DS 1302 ( see link and
program below )
but it doesn't appear to be working.

http://search.atomz.com/search/?sp-q=DS+1302&sp-a=sp052fd900

My debug screen displays the day and that's about it. The time is just
00:00:00, and doesn't start counting or anything ?

Is there just a simple way of seeing if the chip is working ( I have the
32 khz crystal in place and the little dimple at the top as the diagram in
the pdf displays )

Eventually all I want to do is be able to periodically determine what day it
is.

I'm having difficulty understanding what has to be sent to the chip and how
you go about receiving the time back from it ?

Any help would be most appreciated or any links for further info on its use.

Does anyone know the Dallas web site address ? They might have further onfo.

Thanks

Barney



BASIC Stamp II (BS2-IC) Program Listing #1
'***************************************************************************
'* Title: DS1302_1.BS2 Author: Jeff A Martin Date: 5/18/98
*
'*
*
'* Description: This BASIC Stamp II program interfaces to the Dallas Semi.
*
'* DS1302 Real Time Clock (RTC) chip. The date and time is
*
'* read and displayed in long and short formats on the debug
*
'* screen.
*
'*
*
'* Notes: This program can be modified to fit into a smaller code space.
*
'* It is not written as compact as possible to make it more readable
*
'* and to demonstrate all the useful functions of the chip.
*
'* The DS1302 features seconds, minutes, hours (AM/PM-12/24 modes),
*
'* date of month, month, day of week and year time-keeping with
*
'* leap year compensation valid up to 2100. Scratchpad RAM memory
*
'* (31 bytes), single-byte and multi-byte reads and writes, software
*
'* clock-halt, software write-protection, trickle charge and
*
'* operation down to 2.0 volts @ 300 nA are other notable features.
*
'***************************************************************************

'Define I/O pins and RTC variables
Clk CON 0
Dta CON 1
RTCCS CON 2
RTCCmd VAR BYTE
Value VAR BYTE
Seconds VAR BYTE
Minutes VAR BYTE
Hours VAR BYTE
Date VAR BYTE
Month VAR BYTE
Day VAR BYTE
Year VAR BYTE
Idx VAR BYTE

'Define RTC Command Constants
SecReg CON %00000
MinReg CON %00001
HrsReg CON %00010
DateReg CON %00011
MonReg CON %00100
DayReg CON %00101
YrReg CON %00110
CtrlReg CON %00111
TChgReg CON %01000
BrstReg CON %11111

'Define Days-Of-Week, Months and AM/PM text.
'All text is stored in EEPROM with a binary 0 as the end-of-text character
Sun DATA "Sun",0
Mon DATA "Mon",0
Tue DATA "Tues",0
Wed DATA "Wednes",0
Thu DATA "Thurs",0
Fri DATA "Fri",0
Sat DATA "Satur",0

Jan DATA "January",0
Feb DATA "February",0
Mar DATA "March",0
Apr DATA "April",0
May DATA "May",0
Jun DATA "June",0
Jul DATA "July",0
Aug DATA "August",0
Sep DATA "September",0
Oct DATA "October",0
Nov DATA "November",0
Dcm DATA "December",0

AM DATA " AM",0
PM DATA " PM",0

'Set I/O pin states and directions
OUTS = %0000000000000000 'All logic low
DIRS = %0000000000000111 'I/O 0,1 and 2 are output, rest are input

Initialize:
'Set Time and Date to 05/18/98 - 3:00 PM
'NOTE: Date must be set only once for every power-up of DS1302 chip.
Day = $02 'Monday
Month = $05 'May
Date = $18 '18th
Year = $98 '1998
Hours = $15 '3:00 PM (in 24-hour mode)
Minutes = $00
Seconds = $00
GOSUB SetTimeAndDate

Loop:
'Read out all date and time values and display them in two formats on
'the debug screen.
GOSUB ReadRTCBurst
DEBUG HOME,"LONG FORMAT DATE AND TIME:",CR
GOSUB PrintLongDate
GOSUB Print12HourTime
DEBUG CR,CR,"SHORT FORMAT DATE AND TIME:",CR
GOSUB PrintShortDate
GOSUB Print24HourTime
GOTO Loop

'==================== DS1302 Real-Time Clock Subroutines ===================

PrintLongDate:
'Print long date format on debug screen
LOOKUP Day-1,[noparse][[/noparse]Sun,Mon,Tue,Wed,Thu,Fri,Sat],Idx
GOSUB PrintIt
DEBUG "day, "
LOOKUP Month-1,[noparse][[/noparse]Jan,Feb,Mar,Apr,May,Jun,Jul,Aug,Sep,Oct,Nov,Dcm],Idx
GOSUB PrintIt
'NOTE: The following line prints the proper 4-digit year for the years
'1990 through 2089
DEBUG " ",HEX2 Date,", ",DEC2 20-(Year/90),HEX2 Year, CR
RETURN

PrintShortDate:
'Print short date format on debug screen
DEBUG HEX2 Month,"/",HEX2 Date,"/",HEX2 Year, CR
RETURN

Print12HourTime:
'Print 12-hour time format on debug screen
'NOTE: The DS1302 has 12 and 24 hour time-keeping modes (bit 7 of HrsReg
'sets 12/24 mode and bit 5 indicates AM/PM or 20+ hours). For purposes
'of this example, we're using 24 hour mode only, and converting it to
'12-hour in the next two lines below.
DEBUG DEC2 12-(24-(Hours.HIGHNIB*10+Hours.LOWNIB)//12),":",HEX2
Minutes,":",HEX2 Seconds
LOOKUP Hours/$12,[noparse][[/noparse]AM,PM],Idx
GOSUB PrintIt
RETURN

Print24HourTime:
'Print 24-hour time format on debug screen
DEBUG HEX2 Hours,":",HEX2 Minutes,":",HEX2 Seconds
RETURN

PrintIt:
'Prints zero (0) terminated text from EEPROM
READ Idx,Value 'Get next character
IF Value = 0 THEN Finished 'Make sure it's not a binary 0
DEBUG Value 'Display it on screen
Idx = Idx + 1
GOTO PrintIt
Finished:
RETURN

WriteRTCRAM:
'Write to DS1302 RAM Register
HIGH RTCCS
SHIFTOUT Dta, Clk, LSBFIRST, [noparse][[/noparse]%0\1,RTCCmd\5,%11\2,Value]
LOW RTCCS
RETURN

WriteRTC:
'Write to DS1302
HIGH RTCCS
SHIFTOUT Dta, Clk, LSBFIRST, [noparse][[/noparse]%0\1,RTCCmd\5,%10\2,Value]
LOW RTCCS
RETURN

ReadRTCBurst:
'Read all time-keeping registers in one burst
HIGH RTCCS
SHIFTOUT DTA, Clk, LSBFIRST, [noparse][[/noparse]%1\1,BrstReg\5,%10\2]
SHIFTIN DTA, Clk, LSBPRE, [noparse][[/noparse]Seconds,Minutes,Hours,Date,Month,Day,Year]
LOW RTCCS
RETURN

ReadRTCRAM:
'Read DS1302 RAM Register
HIGH RTCCS
SHIFTOUT DTA, Clk, LSBFIRST, [noparse][[/noparse]%1\1,RTCCmd\5,%11\2]
SHIFTIN DTA, Clk, LSBPRE, [noparse][[/noparse]Value]
LOW RTCCS
RETURN

SetTimeAndDate:
'Write time values into all time-keeping registers, being sure to clear
'the write-protect bit in CtrlReg before the write, and set the
'write-protect bit after the write
FOR Idx = 0 TO 8
LOOKUP Idx,[noparse][[/noparse]0,Seconds,Minutes,Hours,Date,Month,Day,Year,128],Value
LOOKUP Idx,[noparse][[/noparse]CtrlReg, SecReg, MinReg, HrsReg, DateReg, MonReg, DayReg,
YrReg, CtrlReg],RTCCmd
GOSUB WriteRTC
NEXT
RETURN

Archiver

If indeed, you are reading what you say from the DS1302, it appears
the interface is working. Its just not counting.

One thought might be that in addition to the crystal, you also need
two shunt cpacitors to ground, one on each side of the crystal. I
usually use 20 pFd.

Peter H Anderson, http://www.phanderson.com

--- In basicstamps@y..., Barney <cafe@e...> wrote:
> Hi,
>
> I am endeavoring to keep time with a RTC DS 1302 but am having a
bit of
> trouble understanding how to do it. I have copied and pasted the
program
> that parallax uses as an example to accompany the DS 1302 ( see
link and
> program below )
> but it doesn't appear to be working.
>
> http://search.atomz.com/search/?sp-q=DS+1302&sp-a=sp052fd900
>
> My debug screen displays the day and that's about it. The time is
just
> 00:00:00, and doesn't start counting or anything ?
>