DS1307 RTC example

[malc-c]

I have an EasyPIC5 development board and one of the Microelectonica RTC2 add on modules which has been breadboarded and needed to be tested as part of an ongoing project. The following example simply shows todays date (14/2/10) and starts running from 19:00 hrs.

Although this example was simply used to test the comms between PIC and Module, it should be a simple matter to add a few tweaks to allow the date and time to be set.

'****************************************************************
'*  Name    : RTCtest877A.BAS                                   *
'*  Author  : Malcolm Crabbe                                    *
'*  Notice  : Copyright (c) 2010 M.Crabbe                       *
'*          : All Rights Reserved                               *
'*  Date    : 14/02/2010                                        *
'*  Version : 1.0                                               *
'*  Notes   : Test of breadboarded RTC2 Module to prove         *
'*          : hardware                                          *
'*  Target  : 16F877A
'****************************************************************

@   __config _HS_OSC & _WDT_ON & _LVP_OFF & _CP_OFF

DEFINE  OSC 20
CLEAR

;----[LCD definitions]------------------------------------------------------
DEFINE LCD_DREG  PORTB              ' LCD Data port
DEFINE LCD_DBIT  0                  ' starting Data bit (0 or 4)
DEFINE LCD_EREG  PORTB              ' LCD Enable port
DEFINE LCD_EBIT  5                  ' Enable bit  (on EasyPIC 5 LCD)
DEFINE LCD_RSREG PORTB              ' LCD Register Select port
DEFINE LCD_RSBIT 4                  ' Register Select bit   (on EasyPIC 5 LCD)
DEFINE LCD_BITS  4                  ' LCD bus size (4 or 8 bits)
DEFINE LCD_LINES 2                  ' number of lines on LCD
DEFINE LCD_COMMANDUS 2000           ' Command delay time in us 
DEFINE LCD_DATAUS 50                ' Data delay time in us 

SDA var PORTC.1                     ' RTC data 
SCL var PORTC.0                     ' RTC clock

TRISC= %11111111
DB0 var byte[8]
CMCON = %00000111                   ' Comparators = off
gosub write_1307
read_1307:                          ' Read time Secs,Mins,Hours,Day,Date,Month,Year,Control
I2CREAD SDA,SCL,$D1,$00,[STR DB0\8] ' Read 8 bytes from DS1307

lcdout $fe,1,"Time=",hex2 DB0[2],":",hex2 DB0[1],":",hex2 DB0[0]    'bit 0=sec, bit 1=min, bit 2=hrs
lcdout $fe,$c0,"Date=",hex2 DB0[4],":",hex2 DB0[5],":",hex2 db0[6]  'bit 4=day, bit 5=month, bit 6=year
goto read_1307
end

Write_1307:                          ' Set time & date to 19:00:00  14th Feb 201
I2CWRITE SDA,SCL,$D0,$00,[$00,$00,$19,$7,$14,$2,$10,$90] ' Write to DS1307
pause 10
RETURN

[Rogerio]

Hi Malcolm.

I'm trying this code but can't make it work. It only displays:

Time= 00:00:00
Date= 00:00:00

but does not show the date and time that was set or advance.

Tried grounding DS1307's Vbat pin and using a lithium battery between this pin and ground. Tried 1k, 4.7K and 10k resistors to Vcc from SCL & SDA.

I know I can write to the DS1307 and I know it's ticking since I can make the SQWE pin stop or go 1 Hz by changing the last byte while writing, I just don't seem to be able to read from it.

I'm using a 16F887 at 4 mhz, pin PortB.1 is SCL, pin PortB.2 is SDA.

Any ideas?

Thanks!

Rogerio

DEFINE  OSC 4
CLEAR

;----[LCD definitions]------------------------------------------------------
DEFINE LCD_DREG  PORTC              ' LCD Data port
DEFINE LCD_DBIT  0                  ' starting Data bit (0 or 4)
DEFINE LCD_EREG  PORTD              ' LCD Enable port
DEFINE LCD_EBIT  0                  ' Enable bit  (on EasyPIC 5 LCD)
DEFINE LCD_RSREG PORTD              ' LCD Register Select port
DEFINE LCD_RSBIT 1                  ' Register Select bit   (on EasyPIC 5 LCD)
'DEFINE LCD_BITS  4                  ' LCD bus size (4 or 8 bits)
'DEFINE LCD_LINES 2                  ' number of lines on LCD
DEFINE LCD_COMMANDUS 2000           ' Command delay time in us 
DEFINE LCD_DATAUS 50                ' Data delay time in us 
SDA var PORTB.2                     ' RTC data 
SCL var PORTB.1                     ' RTC clock
DB0 var byte[8]

TRISB= %11111111
gosub write_1307
read_1307:                          ' Read time Secs,Mins,Hours,Day,Date,Month,Year,Control
I2CREAD SDA,SCL,$D1,$00,[STR DB0\8] ' Read 8 bytes from DS1307
lcdout $fe,1,"Time=",hex2 DB0[2],":",hex2 DB0[1],":",hex2 DB0[0]    'bit 0=sec, bit 1=min, bit 2=hrs
lcdout $fe,$c0,"Date=",hex2 DB0[4],":",hex2 DB0[5],":",hex2 db0[6]  'bit 4=day, bit 5=month, bit 6=year

goto read_1307
end

Write_1307:                          ' Set time & date to 19:00:00  14th Feb 201
pause 1000
I2CWRITE SDA,SCL,$D0,$00,[$00,$00,$19,$7,$14,$2,$10,$80] ' Write to DS1307
pause 10
RETURN

[Rogerio]

Ok, so I had forgoten to clear Anselh register, ha.

Working great now,

Thanks for the code malcolm!

Rogerio

[malc-c]

Glad to hear you've got it working.

It's fairly basic in functionality, I just used it as a test to confirm that the hardware is working (hence no fancy set buttons or alarms etc) - there are other examples on this forum and the net which cover the setting of these things to make a fully functional alarm clock, just use the search function or google

[flipper_md]

this is great!

I'm not too sure to understand how you get the Decimal values when reading as STR and then displaying them as HEX2?

also, a bit out of topic but I get a weird error:
symbol not previously defined (ANSELH)
when trying to set ANSEL = 0, to use other ports.
On a 16F876a...
Ever seen that?

[Rogerio]

also, a bit out of topic but I get a weird error:
symbol not previously defined (ANSELH)
when trying to set ANSEL = 0, to use other ports.
On a 16F876a...
Ever seen that?

Does the 16F876A have an ANSEL or ANSELH register? Some devices use different registers to acomplish similar tasks.