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MSP430FR5739 - Understand low battery voltage through SVS

Davide Sartori
Prodigy 20 points
Other Parts Discussed in Thread: MSP430FR5739, MSP430F5510, MSP-FRAM-UTILITIES, MSP430FR5969

Hi everybody,

I'm  investigating the possibility of saving in FRAM the state of the microcontroller in case of low supply voltage ( < 2.0 V). I don't want to use external hardware or the ADC10 to supervise the supply voltage.  I tried to intercept the interrupt generated by the SVS, but without success. I was only able to figure out after a BOR the cause of the restart. I know that on another micro (e.g. MSP430F5510) there's the possibility of managing the SVM thresholds in order to generate an interrupt when the supply voltage is falling. Has anyone ever tried to do something like that on MSP430FR5739?

Thank you in advance,

Davide

  • 0
    TI__Guru 68116 points
    Hi Davide,

    We actually released something recently for cases like yours (trying to save off data into FRAM when losing power). It's called Compute Through Power Loss (CTPL) and is part of the MSP-FRAM-UTILITIES: www.ti.com/.../msp-fram-utilities
    dev.ti.com/.../

    Please check it out - there is even an example for MSP430FR5739. That example is for using LPM4.5. But if you look at one of the examples for MSP430FR5969 dev.ti.com/.../ that has an example for using the COMP_E comparator module to do the voltage monitoring to detect losing power. FR5739 has a comparator also (COMP_D) so you may be able to port it.

    I hope that this helps!

    Regards,
    Katie
  • 0 in reply to Katie Pier
    Prodigy 20 points

    Dear Katie,

    thank you for the reply. Example code are very interesting, but I was wondering if there is the possibility to intercept a power loss situation in an automatic manner (as  the COMP_E for the MSP430FR5969) exploiting any system interrupt such as SVS or similar without using external hardware. Searching the datasheet and trying some tests, I understand that the reset BOR interrupt due to a SVSH is understandable only after the board reset and hence there's no possibility to save the state of the microcontroller immediately before a BOR event in this way.

    I think that the more efficient solution that seems to be usable is realize a voltage divider powering from an external source and use COMP_E module on MSP430FR5739.

    Regards,

    Davide

  • 0 in reply to Davide Sartori
    TI__Guru 68116 points
    Hi Davide,

    Yes, it is not possible to catch the power loss with SVS for this purpose because it's not possible to get the SVS interrupt before BOR as you noted. So there are basically two options for your case:
    1. Use ADC monitoring of the internal channel connected to Vcc/2, no external components required (though I think you already stated earlier in the thread that you don't want to use the ADC?).
    2. Use the COMP_D on FR57xx in the same way that COMP_E is being used in that FR59xx example (port this to FR57xx - I don't think this will likely take much effort to port). This needs the external resistors for a voltage divider.

    Hopefully one of these options will work for you.
    Regards,
    Katie

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