MSP430 ADC12 multiple channel conversion

Alin Dosa said:

ADC12MCTL0 = ADC12INCH_0+ADC12SREF_1;                 // ref+=AVcc, channel = A0
  ADC12MCTL4 = ADC12INCH_4+ADC12SREF_1+ADC12EOS;        // ref+=AVcc, channel = A3, end seq.

What about 1,2 and 3? The ADC12 works a sequence as if the MCTL registers were a script. It first converts based on MCTL0, then MCTL1, then MCTL2 until it hits the EOS bit. (which might even be set after a reset for one fo the MCTLs you skipped in the setup)

There is no need to configure ADC12MCTL4 for channel 4 nd 0 for channel 0.

The MCTLs can use any input channel. So you can configure MCTL0 for channel 0 and MCTL1 for channel 4 (or even mutiple MCTLs for the same channel, if you want)

Alin Dosa said:

  ADC12IE = 0x10;                           // Enable ADC12IFG.3

It's ADC12IFG.4. However, I gues that's what you wanted anyway.

Another thin I nothiced: you use ADC12SREF_1, but you don't enable the reference anywhere. Won't work. Use ADC12SREF_0 to compare against VCC or enable the internal reference.

 

I am setting the reference previously in the code:

REFCTL0 |= REFON+REFVSEL_1;                   // Set 2.0V reference for ADC

 

I have changed my ADC init function based on your recommendation (and of course then interrupt service routine), and I still get the same behavior (I need to send conversion start twice)

void ADC_Init(void)
{
 
  P6SEL = 0x11;                             // Enable A/D channel inputs
  ADC12CTL0 = ADC12ON+ADC12MSC+ADC12SHT0_8; // Turn on ADC12, set sampling time
  ADC12CTL1 = ADC12SHP+ADC12CONSEQ_1;       // Use sampling timer, single sequence
  ADC12MCTL0 = ADC12INCH_0+ADC12SREF_1;                 // ref+=AVcc, channel = A0

  ADC12MCTL1 = ADC12INCH_4+ADC12SREF_1+ADC12EOS;        // ref+=AVcc, channel = A3, end seq.
  ADC12IE = 0x2;                           // Enable ADC12IFG.2
  ADC12CTL0 |= ADC12ENC;                    // Enable conversions
 
}

#pragma vector = ADC12_VECTOR
__interrupt void ADC12_ISR(void)
{
 
  switch(__even_in_range(ADC12IV,34))
  {
 
  case  0: break;                           // Vector  0:  No interrupt
  case  2: break;                           // Vector  2:  ADC overflow
  case  4: break;                           // Vector  4:  ADC timing overflow
  case  6:                                  // Vector  6:  ADC12IFG0
  //ADC_Result1 = ADC12MEM0;             //store the temperature
  //      ADC_done_flag=1;                                              
             break;     
  case  8:                            // Vector  8:  ADC12IFG1
      ADC_Result1 = ADC12MEM0;             //store the temperature
      ADC_Result2 = ADC12MEM1;             //store the temperature
        ADC_done_flag=1;                                              
             break; 
  case 10: break;                           // Vector 10:  ADC12IFG2
  case 12: break;                           // Vector 12:  ADC12IFG3
  case 14:                            // Vector 14:  ADC12IFG4
                                            
             break; 
 
 
  case 16: break;                           // Vector 16:  ADC12IFG5
  case 18: break;                           // Vector 18:  ADC12IFG6
  case 20: break;                           // Vector 20:  ADC12IFG7
  case 22: break;                           // Vector 22:  ADC12IFG8
  case 24: break;                           // Vector 24:  ADC12IFG9
  case 26: break;                           // Vector 26:  ADC12IFG10
  case 28: break;                           // Vector 28:  ADC12IFG11
  case 30: break;                           // Vector 30:  ADC12IFG12
  case 32: break;                           // Vector 32:  ADC12IFG13
  case 34: break;                           // Vector 34:  ADC12IFG14
  default: break;
  }
}

Any other thoughts?

Alin Dosa said:

I am setting the reference previously in the code:

Okay. I cannot know what you don't post :) A buggy program is like an elephant. You know the joke about the blind men describing an elephant? One was touching the nose ad said "it's a snake", the other was touching the foot and said 'No, it's a tree' while the third was holding the tail and said "you're both wrong, it's a rope".

Alin Dosa said:

ADC12IE = 0x2;                           // Enable ADC12IFG.2

Isn't it ADC12IFG.1? Actually it doesn't enable ADC12IGGx. Those bits are set independently of the IE bit. The IE bit just enables triggering of the ISR (if  the IE bit isn't set, it isn't put into to ADC12IV at all)
Anyway, 0x2 is what you want. You can also use ADC12IE1, which is more clear.

However, I don't see what's wrong with your code.
My own ADC12 init code is similar except one thing: I first set ADC12ON in a separate statement, then I set ADC12MSC and the rest. Maybe the ADC12MSC bit isn't set if you don't enable ADC12ON before (and not at the same time).