Hi there,

I have setup a 16F690 reading a DS1307's time and date (I use RA2/INT interrupt to trigger the process every second), save this data to an external 24LC64 memory, read back what has just been written from the memory and display it.

If I bypass the I2CWRITE/I2CREAD commands, the DS1307 displays time correctly.

But, like in the code here under, after saving RTC's time to the memory, this is what I get after reading back the data from the external memory:
Name: 2016-07-18 23_56_00-LCD Module.jpg Views: 585 Size: 10.5 KB

Data from DT1307 is in BCD format and data conversion, that's where I think I'm wrong, is not my cup of tea

What am I missing?


Code:
'-------------------------------------------------------------------------------
' PIC 16F690 Fuses (MPASM)
@ __Config _FCMEN_OFF &_IESO_OFF &_CPD_OFF &_WDT_OFF &_HS_OSC &_BOR_OFF &_CP_OFF &_PWRTE_OFF &_MCLRE_OFF 

'-------------------------------------------------------------------------------
' Registers   76543210
OPTION_REG = %10000000 'PORT A&B Pull-Ups disabled (look WPUA & WPUB) INTEDG rising edge on A2
ANSEL      = %00000000 'Analog inputs Channels 0 to 7
ANSELH     = %00000000 'Analog inputs Channels 8 to 11
ADCON0     = %00000000 'A/D Module is OFF
CM1CON0    = %00000000 'Comparator1 Module is OFF
CM2CON0    = %00000000 'Comparator2 Module is OFF
INTCON     = %00010000 'INTerrupts CONtrol
TRISA      = %00000100 'Set Input/Output (0 to 5)
PORTA      = %00000000 'Ports High/Low (0 to 5)
TRISB      = %00010000 'Set Input/Output (4 to 7)
PORTB      = %00000000 'Ports High/Low (4 to 7)
TRISC      = %00000000 'Set Input/Output (0 to 7)
PORTC      = %00000000 'Ports High/Low (0 to 7)

'-------------------------------------------------------------------------------
' Defines
DEFINE OSC 4

'-------------------------------------------------------------------------------
' Variables
SQW         VAR PORTA.2     'DS1307's 1Hz output
D_Out       VAR PORTB.7     'serial data out for display
SCL         VAR PORTC.0     'DS1307 clock line
SDA         VAR PORTC.1     'DS1307 data line

DB0         VAR BYTE(8)
DB0(0)      = 0 ' Seconds (00-59)
DB0(1)      = 0 ' Minutes (00-59)
DB0(2)      = 0 ' Hours (00-23)
DB0(3)      = 0 ' Day (01-07; 1=Sunday, 2=Monday, ...)
DB0(4)      = 0 ' Date (01-31)
DB0(5)      = 0 ' Month (01-12)
DB0(6)      = 0 ' Year (00-99)
DB0(7)      = 0 ' Control (see datasheet)

D_Bps       CON 16468   ' 9600 Driven Inverted None

'-------------------------------------------------------------------------------
' Initialize

'-------------------------------------------------------------------------------
' Program
ON INTERRUPT GOTO Read_DS1307

MAIN:
    GOTO MAIN:
END    

'-------------------------------------------------------------------------------
' Interrutp Service Routine
DISABLE
Read_DS1307:      ' Read time Secs,Mins,Hours,Day,Date,Month,Year,Control
    I2CREAD SDA,SCL,$D0,$00,[STR DB0\8] ' Read 8 bytes from DS1307

    ' Write to external memory
    I2CWRITE SDA,SCL,$A0,$00,[DB0(2),DB0(1),DB0(0)]
    PAUSE 10
    
    'Read from external memory
    I2CREAD SDA,SCL,$A0,$00,[DB0(2),DB0(1),DB0(0)]

    SEROUT2 D_Out,D_Bps,[HEX2 DB0(2),":",HEX2 DB0(1),":",HEX2 DB0(0),13,10]

    INTCON.1 = 0  'clear INTF interrupt flag
    RESUME 
ENABLE