Matching time conditions

[isaac]

Why not simply usesomething like a DS1337
where you can have an alarm time and compare it with the current time and if there is a match the DS1337 has a pin that either goes high or low ( cant remember check the data sheet)
This can then be connected to your interupt pin
here is an example
http://www.picbasic.co.uk/forum/show...highlight=toni

Isaac

[malc-c]

Isaac,

many thanks for the link - I'll study that and will look at breadboarding the 1337 chip.

Melanie,

I've looked at the datasheet on many occasions, but to those of us who can only grasp the basics, these datasheets tend to be somewhat daunting, and whilst I don't possess the Rosetta Stone, sometimes Egyptian would probably seem easier than many a datasheet by half

Also, for me I learn far more about PBP from example code written by those more advanced at programming than trying to fathom out the ins and outs of complicated chip structure. After all, this is a forum on PicBASIC Pro. I guess I should of registered at Maxim's forum (assuming one exists) to ask for technical assistance with the data format from the DS1307.

[Melanie]

After all, this is a forum on PicBASIC Pro. I guess I should of registered at Maxim's forum (assuming one exists) to ask for technical assistance with the data format from the DS1307.

Just do as you're told and download that Datasheet!

Then, and ONLY THEN you will be able to compare that I2C Statement with the DS1307's Registers. IT IS the Rosetta stone... until you've looked you won't see it.

I'm NOT being iffy or off-hand with my answer to your query... I'm actually telling you EXPLICITLY that IT WILL HELP YOU UNDERSTAND.

Skip all the crap and jump straight into the section on the Registers... look, it's all laid out crystal clear - it shows you what sequence they're in, how they're addressed, what's inside them... how on earth can you possibly understand what's going on in a piece of code if you don't understand what a particular BYTE of DATA has got inside it at any point in time.

If I told you that Bit 7 of the SECONDS Register was kinda IMPORTANT - How would you know? I could be talking Greek (sorry Ioannis)!

One look, and you know what the $D0 is all about in the I2C Statement. And what about $00 - what's it there for? The answer is screaming at you from the pages of the PBP Manual description of the I2C Command, and the DS1307's Datasheet. The two of them go together hand-in-hand. There's NO other secret document, no Training Course in Electronics or programming... just those two items together allow you fully understand, manipulate and control that chip. Don't handicap yourself unnescessarilly by dismissing it's 'beyond' your understanding. The DS1307 is a simple chip. But more importantly it's a stepping stone on the path to progressing to more complex hardware devices.

Armed with that information, THEN come on the forum and ask your questions. Then folks can point you as to WHY something is the way it is. YOU ASKED about accessing Data out of sequence... that $00 holds the key, and that Datasheet tells you what you should change it to if you wanted just to extract say HOURS. But if I simply said you change it to $02, my answer would be totally meaningless unless you knew WHY!

That is WHY I really PUSH folks to TRY and get to grips with Datasheets. The Ds1307 only has a dozen pages or so, and a chunk of those are irrelevant, so it's not like I'm asking you to digest Tolstoy's War & Peace.

[malc-c]

... And what about $00 - what's it there for? The answer is screaming at you from the pages of the PBP Manual description of the I2C Command, and the DS1307's Datasheet. The two of them go together hand-in-hand.

Mel,

Bear with me on this as I'm sure quite a few of us still have difficulties in getting our heads round bits and bytes and registers etc. But to try and answer your question and see if I've got some grips with the data sheet, here's my take on the above.

$00 is the start of the register address (00H). This byte stores the seconds, bits 0-4 for the digits and bits 5-7 the 10's. The next byte (01H) is the same but for mins. 02H stores the hours, with bit 6 setting the device up for 12/24 hrs depending if set high or low. Bits 0-2 of 03H stores the days, 04H date, 05H month, 06H year (1st 4 bits for digits, last 4 bits decades).

The only part I don't grasp is the $D0 part - The manual stated

I2CREAD DataPin,ClockPin,Control,{Address,}[Var{,Var...}]{,Label}

so in the code I have

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

which transpires as datapin, clockpin, then control. but the only control reference I can find in the data sheet is for SQW (square wave out), and I'm still at a loss as to where you arrive at the $D0

[malc-c]

The only part I don't grasp is the $D0 part -

OK now got it...

from the datasheet The address byte contains
the 7 bit DS1307 address, which is 1101000, followed by the *direction bit (R/W ) which, for a write,
is a 0.

I used a binary to decimal / hex convertor.... 11010000 is D0, therefore the $D0 is the address which the PIC looks for to locate the DS1307 on the I2C buss and sets the DS1307 to either receive data or to send it ?

[Melanie]

You've nailed it Malcolm.

I know I was a bit hard on you, but now you see how simple it all is with that Datasheet and how near impossible it is to understand without.

[malc-c]

Thanks...

Although I now have an understanding of how the DS1307 is accessed and what the registers are... I'm still a long way from understanding a 300 + page data sheet on one of the more complex PICs !, and I must confess I'm still at a loss on how to use the 1307 to match a value in the code an in turn set a value of a variable.

I assume that each byte for each register (01H, 02H etc) is converted from binary into BCD (which I gather is 4bit type code format of binary)... or does pbp simply read each byte at each register.

I guess the simple answer is to wait until I receive the new chip with the alarm function and use that ?