Jman's code for the DS3231
No alarms or offset
Calculation to set Day of the week
Goto settime from the console will set the DS3231 with the current
time and date


' I2C RTC based On DS1307 Secs,Mins,Hours,Day,Date,Month,Year,Control
Dim RTCbuff(7)
Dim Temp(2)
Dim Days$(7)
GoSub Days
i2caddr = &h68 ' DS3231 I2C address
I2C open 100,100 ' Enable I2C
I2C write I2caddr, 0, 1, 0
I2C Read i2caddr, 0, 7, RTCbuff(0) ' Read Time
I2C write I2caddr, 0, 1, 17
I2C Read i2caddr, 0, 2, Temp(0) ' Read Temperature
I2C Close

BCDTEMP = RTCBuff(0)
BCDtoDec BCDTEMP
sec$ = Str$(decimal)

BCDTEMP = RTCBuff(1)
BCDtoDec BCDTEMP
min$ = Str$(decimal)

BCDTEMP = RTCBuff(2)
BCDtoDec BCDTEMP
hours$ = Str$(decimal)

BCDTEMP = RTCBuff(3)
BCDtoDec BCDTEMP
DayOfWeek = decimal

BCDTEMP = RTCBuff(4)
BCDtoDec BCDTEMP
day$ = Str$(decimal)

bcdtemp = rtcbuff(5)
BCDtoDec BCDTEMP
month$ = Str$(decimal)

bcdtemp = rtcbuff(6)
BCDtoDec BCDTEMP
year$ = Str$(decimal + 2000 )

t$ = hours$+":"+min$+":"+sec$
D$ = day$+"/"+month$+"/"+year$
Time$ = T$
Date$ = D$
Temp
Print "Time has been set to ";Time$
Print"Date has been set to ";Date$
Print "Today is ";Days$(DayOfWeek)
Print "Temperature is";Temperature
End


'Temperature
Sub Temp
If Temp(0) < &h80 Then
Temperature= Temp(0) + (Temp(1) / 256)
Else
Temperature=-((Temp(0) Xor &HFF) + 1) + (Temp(1) / 256))
EndIf
End Sub

'Convert to Decimal
Sub BCDtoDec (BCDTEMP)
Decimal = Fix(BCDTemp / 16) * 10
Decimal = Decimal + (BCDTEMP And &hF)
End Sub

Days:
For I = 1 To 7
Read Days$(I)
Next I
Return

Data "Sunday"
Data "Monday"
Data "Tuesday"
Data "Wednesday"
Data "Thursday"
Data "Friday"
Data "Saturday"

SetTime:
' Get time from time$ and date$
tempdec = Val(Left$(Time$, 2))
BCDtoHex TempDec
hours = hex

tempdec = Val(Mid$(Time$, 4, 2))
BCDtoHex TempDec
minutes = hex

tempdec = Val(Right$(Time$, 2))
BCDtoHex TempDec
seconds = hex

tempdec = Val(Left$(Date$, 2))
BCDtoHex TempDec
day = hex

tempdec = Val(Mid$(Date$, 4, 2))
BCDtoHex TempDec
month = hex

tempdec = (Val(Right$(Date$, 4)) - 2000)
BCDtoHex TempDec
year = hex

DayOfWeek

' Write Time to RTC
i2caddr = &h68 ' DS3231 I2C address
I2C Open 100,100 ' Enable I2C
I2C Write i2caddr,0,8,0,seconds,minutes,hours,dow,day,month,year
I2C Close

Print "0=ok 1=nack 2=timeout"; MM.I2C
Print "RTC has been set to ";Time$;" ";Date$
End

'Calculate Day Of Week TZAdvantage's DOW Calculation
Sub DayOfWeek
A = Int(14-Val(Mid$(Date$,4,2)))/12
M = Val(Mid$(Date$,4,2)) + 12*a - 2
Y = Val(Mid$(Date$,7,4)) -a
D = Val(Mid$(Date$,1,2))
Dow=(day+y+Int(y/4)-Int(y/400)+Int(31*m/12)) Mod 7
End Sub

' Convert to Hex
Sub BCDtoHex TempDec
hex = Fix(tempdec / 10) * 16
hex = hex Or ((tempdec / 10) - (Fix(tempdec / 10))) * 10
Return