MSP432P401R: Timer with Button Delay Control:

Shraddha Debata

Part Number: MSP432P401R

how do I configure a button to change the period of the timer. Pressing the button once changes the Timer A toggle delay to 1 second. Pressing the button again changes the Timer A toggle delay to 2 seconds. Lastly, pressing the button a third time changes the Timer A toggle delay back to a half second delay. Additional button presses should cycle through this order. When the system is not toggling the light or handling button presses, it should be in low power mode.

I tried the below code but my loops don't work. It only blinks red. and doesn't toggle the rest of the timer LEDs

My code:-

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//******************************************************************************
// MSP432P401 Demo - Use TimerA in Low-Frequency mode with LPM0
//
//
// Description: Configure device to operate in Low-Frequency LPM0 with TimerA
// running and sourced by a low-frequency clock source. This examples builds
// up on msp432p401_pcm_05, which exercises the transition into LF active mode
// from active mode (LDO).
//
// Note: the code in this example assumes the device is currently in LDO mode
// AM0_LDO or AM1_LDO (Active Mode using LDO, VCore=0/1 respectively)
//
// Transition from DCDC mode to LF requires intermediate transition through
// LDO mode. For more information refer to the PCM chapter in the device user's
// guide.
//
// AM1_DCDC <-----> AM1_LDO <--@--> AM1_LF
// ^
// |
// |
// v
// AM0_DCDC <-----> AM0_LDO* <--@--> AM0_LF
// ^
// |
// |
// v
// LPM0_LF
// *: power state condition after reset
// @: transitions demonstrated in this code example
//
// MSP432P401x
// -----------------
// /|\| |
// | | |
// --|RST |
// | P1.0|--->LED
// | |
//
// William Goh
// Texas Instruments Inc.
// June 2016 (updated) | November 2013 (created)
// Built with CCSv6.1, IAR, Keil, GCC
//******************************************************************************
#include "ti/devices/msp432p4xx/inc/msp.h"
#include <stdint.h>

void error(void);

int main(void)
{
uint32_t currentPowerState;

WDT_A->CTL = WDT_A_CTL_PW | // Stop WDT
WDT_A_CTL_HOLD;

CS->KEY = CS_KEY_VAL ; // Unlock CS module
// Switch MCLK, SMCLK, ACLK sources over to REFO clock for
// low frequency operation first
CS->CTL1 = CS_CTL1_SELM_2 |
CS_CTL1_SELS_2 |
CS_CTL1_SELA_2;
CS->KEY = 0; // Lock CS module

// Get current power state
currentPowerState = PCM->CTL0 & PCM_CTL0_CPM_MASK;

// Transition to Low-Frequency Mode from current LDO power state properly
switch (currentPowerState)
{
case PCM_CTL0_CPM_0: // AM0_LDO, need to switch to AM0_Low-Frequency Mode
while ((PCM->CTL1 & PCM_CTL1_PMR_BUSY));
PCM->CTL0 = PCM_CTL0_KEY_VAL | PCM_CTL0_AMR_8;
while ((PCM->CTL1 & PCM_CTL1_PMR_BUSY));
if (PCM->IFG & PCM_IFG_AM_INVALID_TR_IFG)
error(); // Error if transition was not successful
break;
case PCM_CTL0_CPM_1: // AM1_LDO, need to switch to AM1_Low-Frequency Mode
while ((PCM->CTL1 & PCM_CTL1_PMR_BUSY));
PCM->CTL0 = PCM_CTL0_KEY_VAL | PCM_CTL0_AMR_9;
while ((PCM->CTL1 & PCM_CTL1_PMR_BUSY));
if (PCM->IFG & PCM_IFG_AM_INVALID_TR_IFG)
error(); // Error if transition was not successful
break;
case PCM_CTL0_CPM_8: // Device is already in AM0_Low-Frequency Mode
break;
case PCM_CTL0_CPM_9: // Device is already in AM1_Low-Frequency Mode
break;
default: // Device is in some other state, which is unexpected
error();
}

// Configure TimerA to run off SMCLK = REFO
TIMER_A0->CCTL[0] = TIMER_A_CCTLN_CCIE; // Enable capture compare interrupt
TIMER_A0->CCR[0] = 1000;
TIMER_A0->CTL = TIMER_A_CTL_SSEL__SMCLK | // SMCLK
TIMER_A_CTL_MC__CONTINUOUS; // continuous mode

// Enable TimerA3_CC0 interrupt on the NVIC
NVIC->ISER[0] = 1 << ((TA0_0_IRQn) & 31);

// Enable global interrupt
__enable_irq();

SCB->SCR |= SCB_SCR_SLEEPONEXIT_Msk; // Do not wake up on exit from ISR

// Ensures the SLEEPONEXIT mask is set.
__DSB();

// Go to LPM3
PCM_gotoLPM3();
}

// TimerA3_0 interrupt service routine handler
void TA0_0_IRQHandler(void)
{
int counter = 0;

if((P1IN & 0x02) == 0)
{
if(counter==0)
{
P2->OUT ^= BIT1; // Toggle P1.0 LED
TIMER_A0->CCTL[0] &= ~ TIMER_A_CCTLN_CCIFG;
TIMER_A0->CCR[0] +=256000;
counter=1;
}

else if(counter==1)
{
P2->OUT ^= BIT2; // Toggle P1.0 LED
TIMER_A0->CCTL[0] &= ~ TIMER_A_CCTLN_CCIFG;
TIMER_A0->CCR[0] +=128000;
counter=2;
}

else if(counter==2)
{
P2->OUT ^= BIT3; // Toggle P1.0 LED
TIMER_A0->CCTL[0] &= ~ TIMER_A_CCTLN_CCIFG;
TIMER_A0->CCR[0] +=64000;
counter=0;
}
}
}

void error(void)
{
volatile uint32_t i;

while (1)
{
P2->OUT ^= BIT1;
for(i = 0; i < 20000; i++); // Blink LED forever
}
}

over 4 years ago

0 Chester Gillon over 4 years ago

Guru 92251 points

Shraddha Debata said:
// TimerA3_0 interrupt service routine handler
void TA0_0_IRQHandler(void)
{
int counter = 0;

The counter variable in the timer interrupt service routine which controls changes to the timer delay has automatic scope, and thus is reset to zero every time the timer interrupt handler is entered. Suggest either:

Define counter a global variable
Define counter as a static variable in the TA0_0_IRQHandler()

0 Shraddha Debata over 4 years ago

Prodigy 20 points

the timer is entering all the loops but the button press isn't working. The lights start glowing automatically and they don't blink either.

0 Shraddha Debata over 4 years ago in reply to Chester Gillon

Prodigy 20 points

I declared the counter static as follows:-

void TA0_0_IRQHandler(void)
{
static int counter = 0;

however, my button press doesn't work here and the lights do not toggle for the specific timestamp/interrupt. The lights just glow one after the other but they do not blink with every button press with the respective interrupts.

I have to configure a button to change the period of the timer. Pressing the button once changes the Timer A toggle delay to 1 second. Pressing the button again changes the Timer A toggle delay to 2 seconds. Lastly, pressing the button a third time changes the Timer A toggle delay back to a half second delay.

0 Andy Peters over 4 years ago in reply to Shraddha Debata

Genius 3945 points

So what's keeping you from creating an interrupt triggered when the button is pressed ? Use a falling-edge event. Keep track of the current timer value. In the ISR, check to see what that current value is, and set it to the next one on your list.

Arm-based microcontrollers

Arm-based microcontrollers forum

MSP432P401R: Timer with Button Delay Control: