MSP430F5438A-EP: ADC12 Timer trigger

Dahun Kim

Prodigy 150 points

Part Number: MSP430F5438A-EP

Hello! everyone.

I want to trigger the ADC12 with Timer B.

My plan is Timer B triggers ADC12 about once per 0.1 second.

I configurated the timer B and ADC12. But it didnt worked. where am i missing?

I understood if i SHS in ADC12CTL1 is '10' (TIMER B), ADC12 work every 0.1 seconds.

Did i get it wrong?

My code was working only the first conversion is performed, then not working.

This is my code under the text.

Timer B = UpMode, ACLK, output = toogle ADC12 = A0, Single channel single-conversion, Vref = 2.5V

ACLK = 32,768 Hz

TB0CCR0 = 3275;  
TB0CTL |= TIMER_B_MC_UP + TIMER_B_TBSSEL_ACLK;
TB0CCTL0 = TIMER_B_CCIE+TIMER_B_OUTMOD_4;
TB0CTL |= TIMER_B_TBCLR;

P6SEL |= BIT0;
REFCTL0|= REFON + REFMSTR + REFVSEL_2 + REFTCOFF;

ADC12CTL0 |= ADC12ON + ADC12SHT0_2;
ADC12CTL1 |= ADC12SHS_2 + ADC12SHP;
ADC12MCTL0 |= ADC12SREF_1;
ADC12IE |= ADC12IE0;
ADC12CTL0 |= ADC12SHS_2 + ADC12ENC;

// temp variable = Global variable
#pragma vector = ADC12_VECTOR
__interrupt void ADC12_A_ISR(void)
{
	static int i =0;
    switch(_even_in_range(ADC12IV, 0x24))
		{
			case 0x06:
			    if(i==10) i = 0;
			    temp[i++] = ADC12MEM0;
				break;
			default:
				break;
		}
}

Not using ADC12SC. Because it's not precise.

Anyone help me~!

over 1 year ago

+1 Bruce McKenney47378 over 1 year ago

Guru 91010 points

When using SHS>0, you need to toggle ADC12ENC (=0 then =1) after each conversion in order to get the next trigger [Ref User Guide (SLAU208Q) Sec 28.2.7.1]. The ADC ISR is usually a good place to do this.

-------------------

Unsolicited:

> TB0CCTL0 = TIMER_B_CCIE+TIMER_B_OUTMOD_4;

This enables the CCR0 interrupt, but I don't see an ISR (TIMER0_B0_VECTOR) for it. If you're not interested in the timer interrupt, try:

> TB0CCTL0 = TIMER_B_OUTMOD_4;

OUTMOD=4 (toggle) output runs at half the timer cycle rate, so I expect you're getting a trigger every 0.2 sec. You might want to set TB0CCR0=3275/2.

-----------------

> ADC12CTL0 |= ADC12SHS_2 + ADC12ENC;

The SHS field is in CTL1, not CTL0. This is actually setting SHT0 to something large. Try instead:

> ADC12CTL0 |= ADC12ENC;

0 Dahun Kim over 1 year ago in reply to Bruce McKenney47378

Prodigy 150 points

Thank you for your answer.

I corrected the wrong part after hearing your advice.

1. Quotation (SLAU208Q Sec 28.2.7.1] : 'When any other trigger source is used, ADC12ENC must be toggled between each conversion"

I missed the sentence.

=> I revised ADC12ENC is toggled in ADC12ISR.

#pragma vector = ADC12_VECTOR
__interrupt void ADC12_ISR(void)
{
	static int i =0;
    switch(_even_in_range(ADC12IV, 0x24))
		{
			case 0x06:
			    if(i==10) {i = 0;}
				while(ADC12CTL1 & ADC12BUSY);
			    adc12v.temp[i++] = ADC12MEM0;
				break;
			default:
				break;
		}
	ADC12CTL0 &= ~(ADC12ENC);
	ADC12CTL0 |= ADC12ENC;
}

2. Timer Interrupt

=> In this question, I didn't write time ISR. But in my code, it was in time ISR.

#pragma vector = TIMER0_B0_VECTOR
__interrupt void TIMER0_B0_ISR(void)
{
	P7OUT ^= BIT7; // LED 
}

3. OUTPUT 0.1s

=> I revised TB0CCR0 = 1638-1;

4. ADC12CTL0 |= ADC12SHS_2 + ADC12ENC

=> I revised ADC12CTL0 |= ADC12ENC.

As a result, The ADC is working.

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MSP430F5438A-EP: ADC12 Timer trigger