DS1337 - 12h to 24h mode

[richard]

the code by tabsoft works fine with a ds1307 and the double write is not needed , I have not got a 1337 to test

' pic16f688
 #CONFIG
       __config _INTRC_OSC_NOCLKOUT & _CP_OFF & _WDT_OFF  &  _PWRTE_ON  &  _MCLRE_ON  & _BOD_ON    &  _BOR_ON
 #ENDCONFIG
  
  

        DEFINE OSC 8                 
       DEFINE NO_CLRWDT 1
        CRC VAR BYTE   BANK0 SYSTEM    'CRC
        
            SDApin   var PORTC.0                'SDA
            SCLpin   var PORTC.1               'SCL 
           
            tmp var byte
            pkt var byte[11]
 rtcAMPM   var bit   ' Storage flag to indicate AM or PM ; 0=AM, 1=PM
 hourmode  var bit   ' Storage flag for RTC 12/24 hour mode ; 0=24Hr, 1=12Hr
 BCDResult var byte  ' Storage for temporary result for BCD Conversions
 RTCHour    var byte
          osccon=$70    '8 mhz
          ansel=0       'dig i/o
          CMCON0=7        ' compare off 
                 trisc=%100000
  portc=3
  pause 10


i2cwrite  sdapin,sclpin,$D0,0,[$0,$14,$21,3,$14,1,$14]  'SANE TIME AND DATE  
'i2cwrite  sdapin,sclpin,$D0,0,[0]
 pause 3000  
         serout2 porta.0,84, ["ready",13,10]  
main:

  i2cREAD  sdapin,sclpin,$D0,0,[str pkt \3 ]
      RTCHour = pkt[2]
   if  RTCHour.6 then
   serout2 porta.0,84, [hex2 (pkt[2]&$1f),":",hex2 pkt[1],":",hex2 pkt[0]] 
    if   RTCHour.5 then serout2 porta.0,84, [" pm" ]
     serout2 porta.0,84, [13,10] 
   
   else
   serout2 porta.0,84, [hex2 pkt[2],":",hex2 pkt[1],":",hex2 pkt[0],13,10] 
   endif
    pause 5000
  gosub ampm  
   goto main
   
ampm:

   I2CRead SDApin,SCLpin,$D0,$02,[RTCHour]
   hourmode = RTCHour.6
   if hourmode = 1 then          ' Is the RTC set for 12-hour mode
    rtcAMPM = RTCHour.5          ' Assign AM/PM
    RTCHour = RTCHour & %00011111  ' Bits 4-0 = Hours  0-12
   endif
  BCDResult = RTCHour
  
  gosub Bcd2Dec
  
   
  if hourmode = 1 then  '12Hr Convert to 24Hr
    hourmode = 0    ' change to 24Hr
    if rtcAMPM = 1 then 'PM 
        BCDResult = BCDResult + 12  'PM
    endif
  else  '24Hr Convert to 12Hr
    hourmode = 1
    if BCDResult > 12 then 
        BCDResult = BCDResult - 12
        rtcAMPM = 1
    else
        rtcAMPM = 0
    endif
  endif
  gosub Dec2Bcd
  RTCHour = BCDResult
  RTCHour.6 = hourmode
  RTCHour.5 = rtcAMPM 
  I2cwrite SDApin,SCLpin,$D0,$02,[RTCHour]
  'pause 10
  'I2cwrite SDApin,SCLpin,$D0,$02,[RTCHour]  ' Need to write twice because you changed the mode bit
 
 return 
         
  
 Bcd2Dec:
' Subroutine to convert BCD (2 hex digits) to Decimal
' Make sure to set BCDResult with parameter value before calling this sub  
' Result is stored in BCDResult

    BCDResult = (((BCDResult >> 4) * 10) + (BCDResult & $0f))
    
    return
    
Dec2Bcd:
' Subroutine to convert Decimal to BCD (2 hex digits)
' Make sure to set BCDResult with parameter value before calling this sub  
' Result is stored in BCDResult
     
    BCDResult = (((BCDResult / 10) << 4) | (BCDResult // 10))
    
    return