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CCS/MSP430F5529: Interfacing DS3231 IC USING MSP430F5529 WITH I2C

VIKASH CHANDRA RAMAN
Intellectual 280 points

Part Number: MSP430F5529
Other Parts Discussed in Thread: MSP430F5659

Tool/software: Code Composer Studio

Hello Everyone,

I am doing a project which is called a site monitoring system based on msp430f5529. On that project i am using a DS3231 IC interface with I2C Protocol. i have write the code and its working , its give a accurate time on main power supply, but when its goes for battery i found my time is not accurate , i found 2 sec extra in 48 hours when its goes for battery.

so i request you please cooperate us what is problem behind that 

waiting for your positive response.

vikash chandra raman

COMCON INDUSTRIES

 

  • 0
    TI__Expert 5260 points

    Hello Vikash,

    Time delay on battery is related to DS3231 and it would be better to check with Maxim for the same.. You can check 32KHz signal on battery if there is any change in ppm and report to Maxim about the same.

    Regards,

    Vikas Chola 

  • 0 in reply to Vikas Chola
    Intellectual 280 points

    Hello vikas chola,

    thanks for the replying me, actually we are using AIS Micro Lithium cell CR 2032 3V cmos battery Battery, Is it correct for DS3231 ?

    waiting for your positive response

    vikash chandra raman

    COMCON INDUSTRIES

  • 0 in reply to VIKASH CHANDRA RAMAN
    TI__Genius 17960 points

    Hello Vikash,

    may I ask you why you're trying to use an external RTC? The MSP430F5529 has a built in RTC module, the RTC_A. It supports calendar functions, and allows also calibration. In addition, the ADC module on chip contains a temperature sensor like all our ADC integrated into MSP430 devices. Thus you're able to perform a very accurate temperature compensation of the 32.768kHz based RTC in addition if you want. On top, due to the integration it will be compared with the external I2C interface based RTC probably of significantly lower power consumption. Keep in mind I2C is due to the pull-up resistors never Ultra Low Power communication.

    Best regards

    Peter

  • 0 in reply to VIKASH CHANDRA RAMAN
    TI__Expert 5260 points

    Hello Vikash,

    CR2032 is correct battery , However as I mentioned you should check 32.768KHz accuracy of DS3231  during battery mode, Monitor Battery Voltage on Oscilloscope. If you find any variation you should contact with Maxim with these data.

    As Peter mentioned in his suggestion, you can also use RTC_A and make a battery backup for MSP430F5529 using LPM3.5 with calibration and achieve accurate RTC.  

    Regards,

    Vikas Chola

  • 0 in reply to Peter Spevak
    Intellectual 280 points

    Hello Peter,

    Thanks for reply me, Actually i have already try to run its Own RTC ,its working  but the problem is that there is no option of VBAT, where i can connect the cmos battary, thats why we all decided to use DS3231

    so i would like to asked you sir please suggest me in MSP430F5529 at what pin i will connect the CMOS battary.

    MSP430F5659 There is a provision to interface cmos battary (VBAT) but msp430f5529 doesn't have.

    waiting for your positive reply

    Thanks & Regards

    VIKASH CHANDRA RAMAN

    COMCON INDUSTRIES

    NEW DELHI

    INDIA

  • 0 in reply to VIKASH CHANDRA RAMAN
    TI__Genius 17960 points

    Hello Vikash,

    understand your point. The problem is, the VBAT is a connection related to the power supply architecture of the MSP430 device. In case of the MSP430F5659, the power supply architecture allows the connection of a backup battery.

    With the power supply architecture of the MSP430F5529, like with most of our MSP430 devices, this is not the case. This means you'll have to implement an external circuitry, which enables you using a backup battery for your MSP430 application. How this circuitry needs to look like, is dependent on many factors coming from the expected functionality and other application related requirements.

    Best regards

    Peter

  • 0 in reply to Peter Spevak
    TI__Genius 17960 points

    Hello Vikash,

    please let us know in case you still need support on this. Many thanks in advance.

    Best regards

    Peter

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