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TI Home » TI E2E Community » Support Forums » Microcontrollers » MSP430™ Microcontrollers » MSP430 Ultra-Low Power 16-bit Microcontroller Forum » Using TB0.1 as ADC12SHS
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    Using TB0.1 as ADC12SHS

    This question is answered
    Zack Bomsta
    Posted by Zack Bomsta
    on May 08 2012 11:11 AM
    Intellectual340 points

    Hi All,

    I am trying to configure Timer_B0.1 to be the ADC12 sample-and-hold source select on the MSP430F6636. I have set the ADC12SHS bit to ADC12SHS_3 so as to choose TB0.1 accordingly. I have configured Timer_B to have a period of 3ms, to count in Up-Mode, and I have set TB0CCR1 to be less than TB0CCR0. I am able to verify that the timer is counting to TB0CCR0. It appears to be working correctly; however, the ADC does not seem to be performing any conversions. Do I need to select TB0.1 functionality on the output pin in order for the TB0.1 output to reach the ADC? I hope not, because I have already used that pin as GPIO. Any thoughts on what the issue may be?

    Thanks,  

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    • Jeff Tenney
      Posted by Jeff Tenney
      on May 08 2012 14:44 PM
      Verified Answer
      Verified by Zack Bomsta
      Guru11130 points

      Zack Bomsta
      Do I need to select TB0.1 functionality on the output pin in order for the TB0.1 output to reach the ADC?

      No.

      Some ideas:

      1. Did you configure TB0CCTL1 correctly?
      2. Did you configure the ADC12 correctly?
      3. Are you identifying completed conversion(s) correctly?

      Maybe you could post some code related to these questions.

      Jeff

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    • Jens-Michael Gross
      Posted by Jens-Michael Gross
      on May 09 2012 07:07 AM
      Guru141810 points

      Zack Bomsta
      I have set TB0CCR1

      Did you configure TB0CCR1 for an outmode? If TB0.1 doesn't do anything, it won't trigger a conversion too.
      It is actually the PWM signal generated by the CCR unit (even if not put out to a pin) that is taken as trigger signal.
      So if you don't change the outmode to anything that toggles the TB0.1 signal, nothign will happen.

      Also, you'll have to start the conversion by setting the ADC12SC (and ENC) bit, or the ADC won't do anythign, whether there is a trigger or not.

      The SHP bit controls whether the pulsewidth of TB0.1 controls the samling time, or the internal sampling timer and the SHT_x settings (which of course must be shorter than the TB cycle time, bu tlong enough to sample your signal depending on teh signal source impedance)

      _____________________________________
      Before posting bug reports or ask for help, do at least quick scan over this article. It applies to any kind of problem reporting. On any forum. And/or look here.
      If you cannot discuss your problem in the public, feel free to start a private conversation: click on my name and then 'start conversation'. But please do so only if you really cannot do it in a public thread, as I usually read all threads. And I prefer to answer where others can profit from it (or contribute to it) too.

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    • Zack Bomsta
      Posted by Zack Bomsta
      on May 09 2012 09:00 AM
      Intellectual340 points

      Jeff,

      I was failing on number 3. I was making some incorrect assumptions, but taking a few extra steps to identify a completed ADC showed that it is working! I find that it is usually my faulty assumptions that get me in the most trouble. Thanks for your suggestions.

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    • Zack Bomsta
      Posted by Zack Bomsta
      on May 09 2012 09:09 AM
      Intellectual340 points

      Jens-Michael Gross
       Also, you'll have to start the conversion by setting the ADC12SC (and ENC) bit, or the ADC won't do anythign, whether there is a trigger or not.

      I am not so sure that this is entirely true. I have the ADC performing correct conversions in repeated auto scan mode using TB0.1 as SHS, but I never had to set the ADC12SC in software to get it to work.

      Thanks for your response, you have no idea ho much I have learned by reading your posts on various topics!   

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    • Jens-Michael Gross
      Posted by Jens-Michael Gross
      on May 09 2012 11:22 AM
      Guru141810 points

      Zack Bomsta
      Jens-Michael Gross
       Also, you'll have to start the conversion by setting the ADC12SC (and ENC) bit, or the ADC won't do anything, whether there is a trigger or not.
      I am not so sure that this is entirely true.

      You're right, ADC12ENC alone is sufficient (and required) to allow the conversions to be started by timer.
      I mixed it up with the (not timer triggered) sequence mode, where you have to start the sequence with ADC12SC when using SHP (and individual manipulation of ADC12SC if in extended sample mode)

      Zack Bomsta
      Thanks for your response, you have no idea ho much I have learned by reading your posts on various topics!

      You're welcome. And as you can see, I too still learn (or have to reminded of things I already forgot) :)

      _____________________________________
      Before posting bug reports or ask for help, do at least quick scan over this article. It applies to any kind of problem reporting. On any forum. And/or look here.
      If you cannot discuss your problem in the public, feel free to start a private conversation: click on my name and then 'start conversation'. But please do so only if you really cannot do it in a public thread, as I usually read all threads. And I prefer to answer where others can profit from it (or contribute to it) too.

      Report Abuse
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