DS1307 returns incorrect data ??? [Archive]

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gtvmarty

- 1st October 2009, 07:12

Hi All,

I know how much we dread the DS1307 RTC discussions, but here goes.....

I recently added a DS1307 to my pic16f877 for a data logging project.
I read a serial string into the pic, and send out some serial data with an added time/date stamped onto it for loggin purposes......fairly simple stuff

I can write to the RTCC, and READ from the RTCC with good results...

However, for some reason it displays 90 (yes, NINETY!) seconds before it will increment the minutes.

Also, when the minutes reaches certain numbers, it will jump by 6 mins on the next increment.
For example 12:37:00 will change to 12:43:00 when the next 'minute increment' occurs.

I'm NOT using a 12pf 32,768khz Xtal at the moment, however i thought having the wrong Xtal would only make my clock run slow/fast.

I can't understand where i get 90secs from?

I am writing DECIMAL numbers into the RTCC, not hex etc, as i've seen people writing/reading in 2 different number formats which confused them.

Anyone seen this before?

Thanx,
Marty.

Jerson

- 1st October 2009, 08:18

I use the DS1307 regularly and do not find this behaviour. Perhaps some interrupt routine is disturbing your RTC read? I am not underestimating your skill, but, maybe something is wrong with the code. It will be better if you can post it here for review.

gtvmarty

- 1st October 2009, 09:42

HI there,

Here's the basic code i use, which seems to work, except for the odd figures i mentioned initially.

I2CWrite PORTC.2,PORTC.3,$D0,$00,[0, 15, 15, 5, 1, 10, 9, 10]
'WRITE time and date e.g. this dsets clock to 15:15:00 (3:15pm) on
'Thur (5), 1st (1), October (10), 2009 (9), with control set to "10" for
'a 1Hz pulseout on pin7.

'and later i send this to serial port....
SerOut TX,T9600,["Logged at",#RTCHour,":",#RTCMin,":",#RTCSec,",13,10]

Obviously later, i remmed out the WRITE line, so the pic doesnt keep restarting at the same time/date.

Happy to be pointed out any wrong byte(s) i'm using or missing
Marty.

Darrel Taylor

- 1st October 2009, 09:49

Bit 7 of the seconds register in a 1307 is the "CH" bit, or "Clock Halt".

If that bit is set, you could easily get values of 90+ seconds.
Except that if that bit is set, the clock isn't running.

On initial power-up of a 1307 the internal registers are "undefined", so you actually have to set that bit to 0 to make sure the clock is running.

But if it's counting, and you get 90+ .... OMG.

jonas2

- 1st October 2009, 09:57

Hello

Your routine is correct, try this program

sinoteq

- 1st October 2009, 10:13

Hi
I wounder if you have not done a mistake in how you use the RTC, the DS has a "funny" way to handle numbers. They are BCD coded and can not be written as Decimal numbers straight. You say you write I2CWrite PORTC.2,PORTC.3,$D0,$00,[0, 15, 15, 5, 1, 10, 9, 10]. Please look at the datasheet Timekeeper registers. If you want to load 15 minutes in the DS you have to write it as 21DEC. Why? Becasue the low 4 bits are minutes and the higher 3 bits are 10 minutes so.... Low bits should be 5 (%0101) and then we need 1 ten-minutes thus getting %00010101

Minutes and Hours are kind of straight forward BCD but the Hours register you have to setup for 12pm or 24 hours function and on top of this use BDC codes.

You can not use almost any register from the DS without convering it from BCD code and you get 90 and the strange jumps becasue of this.

gtvmarty

- 1st October 2009, 10:53

Thanx everyone for your responses.

This is my FIRST 1307 project (it just took me several years to get around to trying it out hehehe).

I knew i was close, just a little more fiddling with certain register values and correct bcd data-handling as you all suggested, and i'll be on track.

Thanx again for the friendly support :D
Marty.

jonas2

- 2nd October 2009, 10:02

Hello

It works well try this program.

gtvmarty

- 6th October 2009, 06:10

Sorry guys, getting confused....
Can somebody PLEASE simply adjust "MY" few lines of code (up near top of thread) to show me EXACTLY what i should be writing/reading.

If i write decimal or hex i can't get the right figures.
Someone tells me i can't write in decimal, someone else says i can, and so on.....

If i remove the "#" in my SerOut line, i get NOTHING to come out.

What the ???????
:mad::mad::mad:

gtvmarty

- 6th October 2009, 06:36

Isn't writing $15(hex) the same as 21(dec)???
I see some examples are writing a bunch of hex characters...

I2CWrite PORTC.2,PORTC.3,$D0,$00,[$00, $15, $15, $05, $01, $10, $09, $10]

Marty.

Hi
I wounder if you have not done a mistake in how you use the RTC, the DS has a "funny" way to handle numbers. They are BCD coded and can not be written as Decimal numbers straight. You say you write I2CWrite PORTC.2,PORTC.3,$D0,$00,[0, 15, 15, 5, 1, 10, 9, 10]. Please look at the datasheet Timekeeper registers. If you want to load 15 minutes in the DS you have to write it as 21DEC. Why? Becasue the low 4 bits are minutes and the higher 3 bits are 10 minutes so.... Low bits should be 5 (%0101) and then we need 1 ten-minutes thus getting %00010101

Minutes and Hours are kind of straight forward BCD but the Hours register you have to setup for 12pm or 24 hours function and on top of this use BDC codes.

You can not use almost any register from the DS without convering it from BCD code and you get 90 and the strange jumps becasue of this.

sinoteq

- 6th October 2009, 08:01

Sure is.
But in your first example you did not write hex and then you only get 15 and not 21.

I would start by just writing 0 to all locations and from there start to read the DS once every second. I would do this to make sure I have a routine that can read and display the data in a correct way. When I am sure this is working I would set the DS to a specific time and date and test again.

You need the # in the serout function to convert the data in the variable to ASCII numbers. Without this you do not get nothing, you get a ASCII character that is difficult to detect but you do get something. Yes unless you send NUL :)

DS_CHECK: I2C_Adr_B=0
I2CREAD SDA,SCL,RTC,I2C_Adr_B,[Seconds,Minutes,Hours]
t=Seconds &%00001111
Seconds.7=0
n=Seconds>>4
Seconds=(n*10)+t
I2C_Adr_B=0
t=Minutes &%00001111
n=Minutes>>4
Minutes=(n*10)+t
Hours=Hours &%00001111
System_Time=(Hours*3600)+(Minutes*60)+Seconds
DS_COUNT=0
RETURN

This is one way to use the DS, maybe not the best and most code efficient but it works. Please note that it is only working to 9hours 59min 59 sec because I have not implemented the "10-hour" bit from the Hours register. The equipment I am using will never be on for more than a few hours and I am using the DS as a timer and not as a real RTC. I reset the RTC to 0 at startup.

gtvmarty

- 7th October 2009, 02:30

Although i'm NOW writing as hex data to keep things clear for me, i think my main problem is Reading/converting the 'read data' into correct decimal form.

getting closer ;-)
Marty.

Jerson

- 7th October 2009, 04:44

Look at the DS1307 registers and format your data accordingly. The values you write should be packed BCD values wherever needed.

eg: To write 21 minutes, you need to write HEX 21 to the minutes register. Same for the other registers like hours and seconds. Only make sure to write to the bits needed by the registers.

I haven't used PBP to write a DS1307 yet, but have some C code that works with the IC. Let me know if you wish to look at it for inspiration ;)

mackrackit

- 7th October 2009, 05:24

This is for a DS1337C but it might give you an idea...

Routine to set the RTC:

SET_RTC:
yr = $09
mon = $03
date = $07
sec = $00
mins = $28
hr = $05
I2CWRITE DS_SDA, DS_SCL, RTC, SecReg, [sec,mins,hr,day,date,mon,yr]
RETURN

To READ and send to terminal:

I2CREAD DS_SDA, DS_SCL, RTC, SecReg, [sec,MINs,hr,day,date,mon,yr]
PAUSE 100
SEROUT2 PORTC.6, 16572, [ "TIME ", HEX2 hr, ":", HEX2 MINs, ":",HEX2 sec,$d, $a]
SEROUT2 PORTC.6, 16572, [ "DATE ", HEX2 mon,"-",HEX2 date,"-",HEX2 yr,$d, $a]

gtvmarty

- 7th October 2009, 07:37

Thanx Dave, i'll try that when time allows....

I tried some things from other examples recently, but anything with a DEC2 or HEX2 command in it wouldn't compile for me.

I was using PBP 2.40 with Code Designer lite 1.7, although today i've just purchased PBP 2.60 upgrade (& manual) from local supplier.

Does it sound possible that v2.4 didn't support DEC/HEX commands?

Anyway, back to it :D
Marty.

mackrackit

- 7th October 2009, 11:48

Does it sound possible that v2.4 didn't support DEC/HEX commands?

Not sure, could be.
Make sure your local supplier does not sell you an old version. Get 2.6.

gtvmarty

- 7th October 2009, 11:53

Yep, it IS v2.6 from Dontronics (Aus).

jonas2

- 8th October 2009, 09:54

hello

a good example of converting binary bcd
http://www.picaxeforum.co.uk/showthread.php?t=1051&highlight=DS1307+Correction