Date and Time stamping!!!!

ambivalent · Guest

Hi everyone,

i am interested in date and time stamping (i.e including the current time and date) my data string before storing it into external memory. i am using 16f877a mcu. is this sort of a thing possible. if so, how ?

Take care

Best regards

Mark · Joined: 07 Sep 2003 Posts: 2838 Location: Atlanta, GA

Try searching the forum:
http://www.ccsinfo.com/forum/viewtopic.php?t=23945&highlight=date

kender · Joined: 09 Aug 2004 Posts: 768 Location: Silicon Valley

In a general case, you'll need a surce of date and time for this such as real time clock (RTC, e.g. DS1307) or a GPS receiver.

ambivalent · Guest

Hi everyone!

i have searched the following forum for my date and time stamping problem:

http://www.ccsinfo.com/forum/viewtopic.php?t=23945&highlight=date

however the command printf(__DATE__) gives the date at the compile time, which in my case is no good as i need the date and time update constantly with out having to burn the code again and again.

I guess i would need to use real time clock (RTC, e.g. DS1307) as kender suggested. does ne one have any idea about interfacing this RTC to the 16f877a, how much would it cost me to purchase this RTC hardware

Take care

Best Regards

jecottrell · Joined: 16 Jan 2005 Posts: 559 Location: Tucson, AZ

You can use either a RTC (that will need a lithium back-up battery) or implement a firmware clock.

RTC:
$3.75 for the IC
$4.50 for the battery

Holds time after power down.
Driver available on this forum.

Firmware Clock:
Free
Must set after each power-up.
Must write your own code.

I've done both. I will always use a RTC from now on. You have to decide what's important to you.

Good luck,

John

ambivalent · Guest

Hi everyone

john thankyou for your reply. i believe that the RTC IC option will be the most feasible in my case as i do need the and date to be updated constantly without reprogramming the controller.

can you plz tell me the IC no for which the drivers are available, and also from where these drivers can be found.

and also is the 'date' feature also included in the RTC IC or not?

thankyou very much

Best Regards

jecottrell · Joined: 16 Jan 2005 Posts: 559 Location: Tucson, AZ

First:

Do you have any other peripherals that you need to incorporate? Do they require I2C or SPI? If so, that will help decide which RTC you want to use.

The DS1307 is I2C and I believe the DS1302 is SPI.

Go to the following web page:

http://para.maxim-ic.com/ss.asp?Fam=RTC&Tree=Timers&HP=Timers.cfm&ln=

Check the appropriate boxes (the BUS type is the most relevant).

When trying to find drivers look in your c:/program files/PICC/drivers for an appropriate driver. If that doesn't work, come to this forum and search. I used "ds1307 driver" and received this as one possibility:

http://www.ccsinfo.com/forum/viewtopic.php?t=23255&highlight=ds1307+driver

As always, when using a new component, read the datasheet and make sure you understand what's involved. The 1302 and 1307 are similar but different. One can recharge a b/u battery the other can't.

Yes, most any RTC will support dates. And a variety of other nifty features.... alarms, etc.....

Good luck,

John

ambivalent · Guest

hi
thankyou john for your reply.

can you plz clarify some things as i am new to this field of microcontrollers. what is the significance of I2C or SPI. Another thing is that if i chose ds1307 than what about its power source. Does it need a rechargable battery or does it require +5v from the same source as the microcontroller.

Hope you can help!
Best regards

jecottrell · Joined: 16 Jan 2005 Posts: 559 Location: Tucson, AZ

I2C and SPI are serial communication schemes that are popular in embedded systems. They are relevant in your choice of a specific RTC because you would normally want to stick with one scheme throughout your design for simplicity's sake.

So, if you have any other hardware peripheral requirements, EEPROM, digital pots, etc. you may want to look into what is available. Sticking with a single type will simplify things and reduce the pin count of your MCU. But, if all else fails both SPI and I2C can be implemented simultaneously (if I'm not mistaken.)

If you are going to be logging data you will need some sort of external memory for the data. How much, how fast will, for what cost will help you decide that. Provide details and many expert members of this forum will provide all sorts of ideas.

The power to the RTC must be "un-interruptable" to allow it continue to run when power is removed from the MCU. So, there is typically a coin cell that provides the few uA required for the RTC to continue to run. Depending on the RTC, that may be a rechargeable cell or not. But, that comes later in the decision process.

ckielstra · Joined: 18 Mar 2004 Posts: 3680 Location: The Netherlands

kender · Joined: 09 Aug 2004 Posts: 768 Location: Silicon Valley

I personally always make an oposite choice:

Ttelmah · Guest

I agree.
However it does of course depend on which way you want to transfer data. A software I2C 'slave', can be done, but is _very_ hard indeed, and is not a standard implementation. The 'master' conversely, is very easy to code, and even easier if the library is available. On SPI, the same is true. The master is relatively easy to code either with software or hardware, but the slave is actually hard with either (the SPI slave implementation in the PIC, is to my mind very poor).

Best Wishes