using DS1307

[Scampy]

Following on from my previous threads, the current code for my aquarium controller has been running without issue for the past three days, and has been keeping time very well considering it uses a timer overflow rather than a dedicated time chip like the DS1307 (which the previous version used and kept issuing 10:10:10:10 as the time etc). My new code uses a variable to store a value based on minutes since midnight, and then logic statements are used to determine the phase of the lights (ramp up, on ramp down). This works really well, but as the code is using the internal timers to overflow, the main program loop must be less than the overflow timing, otherwise the clock looses time.

The alternative is to use a DS1307, and but still do the conversion into minutes since midnight as that has proven to be more reliable than doing direct comparison to matching time in Hrs and Min format. However I only really need the HH:MM segment of the time, and I know that the DS1307 has a long string of info stored that includes month, day, year etc. What would be the best way to write / read the DS1307 so that it only gives the hours and minutes and nothing else.

This way if I add features which would otherwise delay the cycle and cause the clock to loose time, with the reading of the DS1307 the counter would still be correct.

The idea is

Counter1 variable word

Read DS1307 to get hours and minutes
Counter1 = (Hours * 60) + minutes

Do logic of if on time >= counter1 then do something etc

[Amoque]

The DS1307 keeps each time "segment" in separate registers, you may read only those you need by standard I2C. From the data sheet, the registers you require are 01H and 02H - minutes and hours respectively. The difficulty is only that the values are stored in BCD format. You may work with them directly, but I find it more intuitive to convert them to decimal, so that every calculation may be done with decimal result.

Below is a snippet from my recent work that reads ALL the DS1337 registers (I am sure they are the same, but '37 is without battery backup) and decodes them to the Debug for verification. You may use the entire code segment or, change the REG_TIM variable to match the first register you require, then collect only two values (as [ MIN, HR]). Also, abbreviate the loop (LP).

SDA/ SCL = PIN DESIGNATIONS, RTC_ADD = ADDRESS, REG_TIM = BEGINNING REGISTER TO READ, REG_VAL[X] = BCD register value from chip.

I2CRead SDA, SCL, RTC_ADD, REG_TIM, [REG_VAL[0], REG_VAL[1], REG_VAL[2], REG_VAL[3], REG_VAL[4], REG_VAL[5], REG_VAL[6]]
FOR LP = 0 TO 6 ' For each register
D0 = (REG_VAL[LP] >> 4) * 10 ' Decode 10's digit
D1 = REG_VAL[LP] & %0001111 ' Blank 10's, get 1's
REG_VAL[LP] = D0 + D1 ' Write Decimal value to register
NEXT LP ' Next register

DEBUG "TIME:[", dec1 REG_VAL[3], "] ", dec2 REG_VAL[5], "/", dec2 REG_VAL[4], "/", dec2 REG_VAL[6], " ", dec2 REG_VAL[2], ":", dec2 REG_VAL[1], ":", dec2 REG_VAL[0], 10

Debug should print TIME:[DOW] MO/DAY/YR HR:MN:SC and each REG_VAL[X] should contain the decimal value of the segment indicated.

At this point, then... Multiply HR * 60 + MN. Of course I (elsewhere) set my clock to 24 hour mode - or also read the AM/PM bit and add 12 hours as required.

[Scampy]

Thanks for the info.

From a previous example I have:

I2CRead SDApin,SCLpin,$D0,$00,[RTCSec,RTCMin,RTCHour,RTCWDay,RTCDay,RTCMonth,RTCYear,RTCCtrl]  ; read DS1307 chip

My question is would I need to read every bit or could I get away with

I2CRead SDApin,SCLpin,$D0,$00,[,RTCMin,RTCHour,,,,,]  ; read DS1307 chip

How would I get it to ignore the first bit (rtcsec) accept the next two bits and ignore the rest... or doesn't it work that way ?

[Amoque]

You need not read any that you do not require.

I2CRead SDApin,SCLpin,$D0,$01,[,RTCMin, RTCHour] ; read DS1307 chip

Will begin reading at register $01 (note change I made to your code) and collect two registers in the variables (RTCMin, RTCHour) you provided. Like that you have BCD minutes and hours.

Also, remove the leading comma in the variable list as: [RTCMin, RTCHour]

[Scampy]

Cheers - Between our replies I found that I could do as you suggested, although I didn't know about the $01 address part. I assume where I had $00 the is the RTCSec bit, so using the $01 tells the code to read from the second bit (RTCMIN) ?

Thanks for your help

[Amoque]

Yes, but understand only that where you use the word "bit" is actually a byte. $00 is "%00000000", $01: "%00000000" ... like that. It is how you can read and write the AM/PM bit and read Status bits to verify the clock is running:

IF RTCHour.6 = 0 then 24H mode enabled.

Enjoy...

[Scampy]

Hi,

Thanks for your help... The following code works fine for just hours and minutes.

Posted here for reference should anyone else need this.

18F4520 - running with a 20mhz crystal - 4x20 LCD

ASM 
  __CONFIG    _CONFIG1H, _OSC_HSPLL_1H
  __CONFIG    _CONFIG2L, _PWRT_ON_2L  
  __CONFIG    _CONFIG2H, _WDT_ON_2H & _WDTPS_512_2H
  __CONFIG    _CONFIG3H, _MCLRE_ON_3H & _LPT1OSC_OFF_3H & _PBADEN_OFF_3H  
  __CONFIG    _CONFIG4L, _LVP_OFF_4L & _XINST_OFF_4L
ENDASM

DEFINE  OSC 48  ; config settings 18F4580, 20mhz crystal
ADCON1 = $0F
clear

	RTCMin var byte		' Minutes
	RTCHour var byte	' Hours
	RTCCtrl var byte	' Control 
                   
SCLpin var PORTC.3               ' RTC pin - clk
SDApin var PORTC.4               ' RTC pin - data	

Hours             var byte
Minutes           var byte	

	CounterA var byte	' General purpose Variable
	CounterB var byte	' General purpose Variable
	CounterC var byte	' General purpose Variable
	CounterD var byte	' General purpose Variable
	
	SetMN var byte		' Minutes
	SetHR var byte	' Hours


'analog settings

ADCON0 = 0                      'Set ADCON0
ADCON1 = %00001111              'Set D i/o
CMCON = 7                       'Disable Comparators

PR2 = 249 
'****************************************************************
'Port settings

CCP1CON = %00001100             ' 
CCP2CON = %00001100             '     
TRISA  = %11101111              'set PORTA as all output apart from 0,1,2
TRISB  = %00000011 
TRISD  = %00000011              'set PORTB as all output apart from 0&1
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 4               ' number of lines on LCD
DEFINE LCD_COMMANDUS 2000        ' Command delay time in us 
DEFINE LCD_DATAUS 50             ' Data delay time in us 

setHR = 12
setMN = 01

'	Save Minutes
'	------------
			CounterA=SetMN
			Gosub ConvertBCD
			RTCMin=CounterB
'
'	Save Seconds
'	------------
			CounterA=SetHR
			Gosub ConvertBCD
			RTCHour=CounterB

I2cwrite  SDApin,SCLpin,$D0,$01,[RTCMin,RTCHour]  ; read DS1307 chip
		
main:		
I2CREAD SDApin,SCLpin,$D0,$01,[RTCMin,RTCHour]  ; read DS1307 chip

	LCDOut $FE,$80
If RTCHour.6=1 then
			
CounterA=(RTCHour>>4)&$01                           ' Work-Out 12 or 24 hour Display for Hours
else
CounterA=(RTCHour>>4)&$03
endif
CounterA=CounterA*10+(RTCHour&$0F)                  ' Display Hours appropriately for 12 or 24 hour Mode 
If RTCHour.6=1 then			
LCDOut $FE,$D4,#CounterA
else
LCDOut $FE,$D4,#CounterA Dig 1,#CounterA Dig 0
endif
LCDOut ":",#(RTCMin>>4)&$0F,#RTCMin&$0F,"   "

	Goto main
ConvertBCD:
	CounterB=CounterA DIG 1                        ' CounterA is the entry variable
	CounterB=CounterB<<4                           ' CounterB holds the converted BCD result on exit
	CounterB=CounterB+CounterA DIG 0
	Return

It's all rough and ready... now to convert the Hours and minutes into the value for a counter and try this in my next version of aquarium lighting

Thanks for your contribution - steep learning curve but I'm getting there

[Scampy]

OK, whilst the RTC is working fine with just reading and writing RTCHours and RTCMin, I'm having issues converting the time into minutes so I can use the variable Counter1 to store that value which is then used in the logic within my code to trigger case statements.

For example 14:00 hrs would equate to 840 minutes as the counter is reset to 00:00 at midnight. 14 * 60 = 840. 14:01 would thus be 841 etc

I've tried the following

If RTCHour.6=1 then
			
CounterA=(RTCHour>>4)&$01                           ' Work-Out 12 or 24 hour Display for Hours
else
CounterA=(RTCHour>>4)&$03
endif
CounterA=CounterA*10+(RTCHour&$0F)                  ' Display Hours appropriately for 12 or 24 hour Mode 
If RTCHour.6=0 then			
LCDOut $FE,$D4,#CounterA
else
LCDOut $FE,$D4,#CounterA Dig 1,#CounterA Dig 0
endif
LCDOut ":",#(RTCMin>>4)&$0F,#RTCMin&$0F,"   "
MM=(RTCMin>>4)&$0F+RTCMin&$0F
Counter1 = (counterA*60)+MM

But using this 13:57 gives a value of 784, when it should be 837.... anyone have any suggestions ?

[richard]

you need to put the rtc seconds into your ss var , so the leds can ramp up/down

[Scampy]

Doh !!!

I obviously had spent too long looking at this screen...... that's obvious now you've pointed that out... All working now

Thanks Richard

[richard]

I hope your screen isn't green like your prev post , I nearly went blind trying to read your red and green sections

cheers richard

[Amoque]

It appears even fish have something to be thankful for on Thanksgiving!

As a younger man I kept tropical varieties and had the greatest joy from watching their antics. Reading through your code I imagine a very cool arrangement for lighting that simulates a cycle much more natural than my own habit of turning off the lights at bed time! I can hardly wait for version "2" of your software that incorporates the calendar for seasonal adjustments of daylight hours. Perhaps you think this will not happen, but I think it will - sometime. I recall that keeping fish compelled me always to "futz" with this and improve on that to make their environment more natural and realistic; I think your project shows you are the same? In fact, have you not also thought of the sensors that measure Ph and the devices (Peltier?) that might control heat and cool? Then there is dissolved oxygen, clarity, water level, feeding...

Congratulations on both the completed project and mastering the skills... I find nothing more satisfying than creation by my own hand; perhaps you are the same in this too?

[Art]

Another option, depending on real natural light available, is to have the pic learn the
real daylight cycle so you never have to set the clock.
This is what some solar controllers with auto night light output do to figure out when
to turn night lights on and off.
They are designed to use on remote toilet blocks and such, and would not be subject
to getting thrown off too much by the home lights being turned on and off.