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MSP430f6638 Ref voltage by ADC12CTL0 or ADC12MCTL

jim wang2
Intellectual 270 points
Other Parts Discussed in Thread: MSP430F6636

Hi there are two registers ADC12CTL0 or ADC12MCTL can set the ADC REF voltage,  

ADC12REFON  and ADC12REF2_5V of ADC12CTL0

ADC12SREFx of ADC12MCTL

what is different between them? and I only can select one, right?

do you have some sample code of ADC application for MSP430f6636 ?

thanks

  • 0
    Guru 74080 points

    Hi Jim!

    Code examples for the processor can be downloaded here. For the ADC there are

    • msp430f66xx_adc_01.c              ADC12, Sample A0, Set P1.0 if A0 > 0.5*AVcc
    • msp430f66xx_adc_02.c              ADC12, Using the Internal Reference
    • msp430f66xx_adc_05.c              ADC12, Using an External Reference
    • msp430f66xx_adc_06.c              ADC12, Repeated Sequence of Conversions
    • msp430f66xx_adc_07.c              ADC12, Repeated Single Channel Conversions
    • msp430f66xx_adc_08.c              ADC12, Using A8 and A9 Ext Channels for Conversion
    • msp430f66xx_adc_09.c              ADC12, Sequence of Conversions (non-repeated)
    • msp430f66xx_adc_10.c              ADC12, Sample A10 Temp and Convert to oC and oF

    Dennis

  • 0
    TI__Prodigy 335 points
    Hello Jim,

    with the ADC12REF2_5V setting in ADC12CTL0 you can control the voltage level of the internal reference.

    With ADC12SREFx instead you control the reference which should be used for a ADC channel (e.g. AVcc/AVss or Vref+/AVss).

    The ADC12REFON bit and the ADC12REF2_5V bits can be used to control the internal reference but it is a better choice to control the internal reference with the bits in REFCTL0 register,

    Best regards,

    Michael
  • 0 in reply to Michael Weber
    Intellectual 270 points

      if following code running, the A/D will convert only A0 to A2 or A0 to A7 ?

      ADC12CTL1 = ADC12SHP+ADC12CONSEQ_1;       // Use sampling timer, single sequence
      ADC12MCTL0 = ADC12INCH_0;                 // ref+=AVcc, channel = A0
      ADC12MCTL1 = ADC12INCH_1;                 // ref+=AVcc, channel = A1
      ADC12MCTL2 = ADC12INCH_2;                 // ref+=AVcc, channel = A2

    thanks

    jim

  • 0 in reply to jim wang2
    TI__Prodigy 335 points

    Hello Jim,

    in your example the ADC converts channel A0 to A2. For conversion of A0 to A7 you have to extend your example with:

    ADC12MCTL3 = ADC12INCH_3;

    ADC12MCTL4 = ADC12INCH_4;

    ADC12MCTL5 = ADC12INCH_5;

    ADC12MCTL6 = ADC12INCH_6;

    ADC12MCTL7 = ADC12INCH_7 + ADC12EOS;

    As you can see in the code you have to set the ADC12EOS-Bit for the last channel to indicate the end of the measurement sequence.

    Best regards,

    Michael

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