How to use MSP430FR5849 Window Comparator within LPM3/4

Section 28.2.1.1 of the User's Guide says:

The user must ensure that the clock that is used for ADC12CLK remains active until the end of a conversion.

So you have to use a clock that isn't stopped, such as ACLK in LPM3.

Hi Clemens-san,

Think you for your information.

But, our customer already implemented suggested code.
Please look the testing code below and let us know what is problem?
This code (using LPM3) is modified from msp430fr59xx_adc12_21.c (using LPM0).
//******************************************************************************
// MSP430FR59xx Demo - ADC12, Window Comparator, 2.5V ref
//
// Description; A1 is sampled in single ch/ single conversion mode.
// Window comparator is used to generate interrupts to
// indicate when the input voltage goes above the High_Threshold or below the
// Low_Threshold or is in between the high and low thresholds. TimerB0 is used
// as an interval timer used to control the LED at P1.0 to toggle slow/fast
// or turn off according to the ADC12 Hi/Lo/IN interupts.
//
// MSP430FR5969
// -----------------
// /|\| XIN|-
// | | | 32kHz
// --|RST XOUT|-
// | |
// >---|P1.1/A1 P1.0 |--> LED
//
// Priya Thanigai
// Texas Instruments Inc.
// February 2014
// Built with IAR Embedded Workbench V5.60 & Code Composer Studio V5.5
//******************************************************************************
#include "msp430.h"

#define High_Threshold 0x333 // ~500mV
#define Low_Threshold 0x199 // ~250mV

volatile unsigned int SlowToggle_Period = 20000-1;
volatile unsigned int FastToggle_Period = 1000-1;

int main(void)
{
WDTCTL = WDTPW | WDTHOLD; // Stop WDT

// Configure GPIO
P1OUT &= ~BIT0; // Clear P1.0
P1DIR |= BIT0; // Set P1.0 output direction
P1SEL1 |= BIT2; // Configure ADC P1.2/A2
P1SEL0 |= BIT2;
PJSEL0 |= BIT4 | BIT5; // For XT1

// Disable the GPIO power-on default high-impedance mode to activate
// previously configured port settings
PM5CTL0 &= ~LOCKLPM5;

// Clock System Setup
CSCTL0_H = CSKEY >> 8; // Unlock CS registers
CSCTL1 = DCOFSEL_3; // Set DCO to 8MHz
CSCTL2 = SELA__LFXTCLK | SELS__DCOCLK | SELM__DCOCLK;
CSCTL3 = DIVA__1 | DIVS__8 | DIVM__8; // MCLK = SMCLK = 1MHz
CSCTL4 &= ~LFXTOFF; // Enable LFXT1

do
{
CSCTL5 &= ~LFXTOFFG; // Clear XT1 fault flag
SFRIFG1 &= ~OFIFG;
}while (SFRIFG1&OFIFG); // Test oscillator fault flag
CSCTL0_H = 0; // Lock CS registers

// Configure ADC12
// tsample = 16ADC12CLK cycles, tconvert = 14 ADC12CLK cycles
// software trigger for SOC, MODOSC, single ch-single conversion,
// tsample controlled by SHT0x settings
// Channel 1, reference = internal, enable window comparator
// Set thresholds for ADC12 interrupts
// Enable Interrupts
ADC12CTL0 = ADC12SHT0_2 | ADC12ON;
ADC12CTL1 = ADC12SHS_0 | ADC12SSEL_1 | ADC12CONSEQ_0 | ADC12SHP; /* ACLK */
ADC12MCTL0 = ADC12INCH_2 | ADC12VRSEL_1 |ADC12WINC;
ADC12HI = High_Threshold;
ADC12LO = Low_Threshold;
ADC12IER2 = ADC12HIIE | ADC12LOIE | ADC12INIE;

// Configure internal reference
while(REFCTL0 & REFGENBUSY); // If ref generator busy, WAIT
REFCTL0 |= REFVSEL_2|REFON; // Select internal ref = 2.5V
// Internal Reference ON
while(!(REFCTL0 & REFGENRDY)); // Wait for reference generator
// to settle

// Configure TB0 period-timer for LED toggle
TB0CCTL0 = CCIE; // CCR0 interrupt enabled
TB0CTL = TBSSEL__ACLK | TBCLR; // ACLK, clear TBR

while(1)
{
ADC12CTL0 |= ADC12ENC | ADC12SC; // Enable & start conversion
__bis_SR_register(LPM3_bits | GIE); // Enter LPM3 w/ interrupts
__no_operation(); // for debugger
}
}

#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector = ADC12_VECTOR
__interrupt void ADC12_ISR(void)
#elif defined(__GNUC__)
void __attribute__ ((interrupt(ADC12_VECTOR))) ADC12_ISR (void)
#else
#error Compiler not supported!
#endif
{
switch(__even_in_range(ADC12IV, ADC12IV_ADC12RDYIFG))
{
case ADC12IV_NONE: break; // Vector 0: No interrupt
case ADC12IV_ADC12OVIFG: break; // Vector 2: ADC12MEMx Overflow
case ADC12IV_ADC12TOVIFG: break; // Vector 4: Conversion time overflow
case ADC12IV_ADC12HIIFG: // Is A1 > 2V?: High Interrupt
ADC12IFGR2 &= ~ADC12HIIFG; // Clear interrupt flag
TB0CTL &= ~MC__UP; // Turn off Timer
TB0CCR0 = FastToggle_Period; // Set Timer Period for fast LED toggle
TB0CTL |= MC__UP;
__bic_SR_register_on_exit(LPM3_bits); // Exit active CPU
break;
case ADC12IV_ADC12LOIFG: // Is A1 < 1V?: Low Interrupt
ADC12IFGR2 &= ~ADC12LOIFG; // Clear interrupt flag
TB0CTL &= ~MC__UP; // Turn off Timer
TB0CCR0 = SlowToggle_Period; // Set Timer Period for slow LED toggle
TB0CTL |= MC__UP;
__bic_SR_register_on_exit(LPM3_bits); // Exit active CPU
break;
case ADC12IV_ADC12INIFG:
ADC12IFGR2 &= ~ADC12INIFG; // Clear interrupt flag
TB0CTL &= ~MC__UP; // Turn off Timer
P1OUT &= ~BIT0; // Turn off LED
// __bic_SR_register_on_exit(LPM3_bits); // Exit active CPU
break; // Vector 10: ADC12IN
case ADC12IV_ADC12IFG0: break; // Vector 12: ADC12MEM0
case ADC12IV_ADC12IFG1: break; // Vector 14: ADC12MEM1
case ADC12IV_ADC12IFG2: break; // Vector 16: ADC12MEM2
case ADC12IV_ADC12IFG3: break; // Vector 18: ADC12MEM3
case ADC12IV_ADC12IFG4: break; // Vector 20: ADC12MEM4
case ADC12IV_ADC12IFG5: break; // Vector 22: ADC12MEM5
case ADC12IV_ADC12IFG6: break; // Vector 24: ADC12MEM6
case ADC12IV_ADC12IFG7: break; // Vector 26: ADC12MEM7
case ADC12IV_ADC12IFG8: break; // Vector 28: ADC12MEM8
case ADC12IV_ADC12IFG9: break; // Vector 30: ADC12MEM9
case ADC12IV_ADC12IFG10: break; // Vector 32: ADC12MEM10
case ADC12IV_ADC12IFG11: break; // Vector 34: ADC12MEM11
case ADC12IV_ADC12IFG12: break; // Vector 36: ADC12MEM12
case ADC12IV_ADC12IFG13: break; // Vector 38: ADC12MEM13
case ADC12IV_ADC12IFG14: break; // Vector 40: ADC12MEM14
case ADC12IV_ADC12IFG15: break; // Vector 42: ADC12MEM15
case ADC12IV_ADC12IFG16: break; // Vector 44: ADC12MEM16
case ADC12IV_ADC12IFG17: break; // Vector 46: ADC12MEM17
case ADC12IV_ADC12IFG18: break; // Vector 48: ADC12MEM18
case ADC12IV_ADC12IFG19: break; // Vector 50: ADC12MEM19
case ADC12IV_ADC12IFG20: break; // Vector 52: ADC12MEM20
case ADC12IV_ADC12IFG21: break; // Vector 54: ADC12MEM21
case ADC12IV_ADC12IFG22: break; // Vector 56: ADC12MEM22
case ADC12IV_ADC12IFG23: break; // Vector 58: ADC12MEM23
case ADC12IV_ADC12IFG24: break; // Vector 60: ADC12MEM24
case ADC12IV_ADC12IFG25: break; // Vector 62: ADC12MEM25
case ADC12IV_ADC12IFG26: break; // Vector 64: ADC12MEM26
case ADC12IV_ADC12IFG27: break; // Vector 66: ADC12MEM27
case ADC12IV_ADC12IFG28: break; // Vector 68: ADC12MEM28
case ADC12IV_ADC12IFG29: break; // Vector 70: ADC12MEM29
case ADC12IV_ADC12IFG30: break; // Vector 72: ADC12MEM30
case ADC12IV_ADC12IFG31: break; // Vector 74: ADC12MEM31
case ADC12IV_ADC12RDYIFG: break; // Vector 76: ADC12RDY
default: break;
}
}

// Timer1 B0 interrupt service routine
#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector=TIMER0_B0_VECTOR
__interrupt void TIMER0_B0_ISR(void)
#elif defined(__GNUC__)
void __attribute__ ((interrupt(TIMER0_B0_VECTOR))) TIMER0_B0_ISR (void)
#else
#error Compiler not supported!
#endif
{
P1OUT ^= BIT0; // Toggle LED P1.0
}

Best Best Regards,

Why is the __bic_SR_register_on_exit() call commented out?

Hi Clemens-san,

Thank you for the comment.

This is a low power application and we need to use the MSP430 at LPM3 mode
as much as possible. The power consumption will be more if we use ADC all the time.

And we believe window comparator should be useful in this case,
we thought that using window comparator we could check the threshold level and execute
ADC only if the value is above the threshold level.

If we comment out "__bic_SR_register_on_exit()" every time the CPU goes to
active state in the ADC interrupt handler and ADC gets triggered.
And the power consumption is too much(around 1mA) comapared to the LPM3 mode.

Window Comparator won't be a meaningful feature if we cannot use it in the LPM3 mode.
Please let me know your suggestions.

Best Regards,