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MSP430F55xx Comp_B with two external inputs?

Henry Lehmann
Prodigy 170 points
Other Parts Discussed in Thread: MSPWARE

Hi all,

I have looked through the user's guide and the MSPWare code examples for Comb_B and see no mention of being able to use two external inputs with the onboard comparator simultaneously.  In our case, we would like to use an external DC reference on the V- and a sine wave on V+ so we can find the zero-crossing point of said sine wave.  It appears that one of the inputs must always be connected to the internal reference or resistive ladder, which doesn't help us since the voltage isn't correct and will interfere with our external reference.  Am I understanding this correctly, or did I miss something?

Thanks!

-Henry

  • 0
    TI__Genius 16165 points

    Henry,

    You actually can provide external sources to both minus and positive terminals of the Comp_B. In SLAU208, see section 31.2.6 where it talks about "If external signals are applied to both comparator input terminals, the internal reference generator should be turned off."

    Then in your code you would just need to enable CBIMEN and CBIPEN bits in CBCTL0 register.

    Regards,

    William

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