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MSP430F2274: Internal OP-AMP configuration, light sensor

Mirco Franchetti42
Intellectual 560 points

Part Number: MSP430F2274

Hello,

I'm working with internal OP-AMP OA0, acting as a unity gain buffer and taking the voltage level from a phototransistor tied to A0 (P2.0).

My question is about OA0 to ADC10 connection. User Guide states that the output can be internally routed to analog input A1 AND his relative pin P2.1.

What does it imply?

I mean, do i have to set the A1 bit in ADC10AE0 register for using A1 for conversion? If not, will the P2.1 (A1) pin be influenced by OA0 output? 

I physically realized that if the bit in ADC10AE0 is set, the measures are reliable but I'm still in doubt about what I've done.

Thank you in advance!

Mirco

  • 0
    TI__Genius 14800 points

    Hello Mirco,

    After reading the OP-AMP and ADC sections of the User's Guide, it seems to be that you are using the peripherals as they are intended to be used for your application. From the chart below, it can be seen that the OA output can be strictly externally routed, strictly internally routed, or a combination of the both.

    Once the output is set to be routed to the ADC (A1), you must set the A1 bit in the ADC10AE0 to enable the analog conversion for that channel. If the bit is not set, the ADC A1 channel will not be enabled; however, if the OA0 output was externally routed you would still be able to see the OA0 output on P2.1 regardless of the A1 bit in ADC10AE0. Hopefully this clears things up a little bit and assures you that the way you have configured it is the proper configuration for routing the OA0 output to the appropriate ADC channel.

    Best regards,

    Matt Calvo

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