LED BRIGHTNESS CONTROL USING SWITCH

Hi Neena!

I would drive the LED at an output pin that can be hardware-controlled by a timer and operate it in OUTMOD_7 (reset/set). Then I would set a fixed frequency with CCR0 and a variable duty-cycle in CCRx. Then check the buttons and increase CCRx by a fixed value when pressing one button and decrease CCRx by the value when pressing the other one.

Dennis

Hi

I am also attached my code with this case.Could you please check that there is any mistakes is there in that code.

PWM dimming LEDs don't have to be to be fast as anything over 100-200 Hz looks smooth to a human eye.

So say you are using 1MHz DCO for  taclk source.
1'000'000/200 = 500-1 to be used for the CCR0 value

Set CCR1 to 20 and use CCR0's IRQ to increase it each 16th cycle until it reach 480.

With a msp that has no store-and-latched Timmer, then comes the problems of not changing it in time so don't go below 20 for ccr1

once you got this working, your are ready to use buttons to change CCR1 value.

Hi Tony,

Now I changed the code in the following way.Now we have four LEDs and two different brightness levels are there.But now the problem is that when we are working continously the PWM output get changed.That means one become zero and zero become one.So the duty cycle will change.Before the problem occur the duty cycle was (10%-58%) but after this toggling issue the duty cycle was (62%-90%).

#include <msp430.h>
#define THRESHOLD0 0x0000
#define THRESHOLD1 0x0136
#define THRESHOLD2 0x026c
#define THRESHOLD3 0x03a2
#define hystyrisis 0x005D

#define TIM1 120

#define TIM2 560
#define VAR 1
int main(void)
{

WDTCTL = WDTPW + WDTHOLD; // Stop WDT

BCSCTL1 = CALBC1_16MHZ;
DCOCTL = CALDCO_16MHZ;

ADC10CTL1 = INCH_0; // Conversion code singed format, input A0
ADC10CTL0 = ADC10SHT_2 + ADC10ON + ADC10IE; // ADC10ON, interrupt enabled
ADC10AE0 |= 0x00; // P1.0 ADC option select

// Set P1.0 LED on

P2DIR |= 0x0F; // P1.0 output
P2OUT |= 0x00;

CCTL1 = CCIE + OUTMOD_7; // CCR1 interrupt enabled
CCTL2 = CCIE + OUTMOD_7; // CCR2 interrupt enabled
CCR1 = 100;
CCR2 = 100;
CCR0 = 1000;
TACTL = TASSEL_2 + MC_3; // SMCLK, Contmode

for (;;)
{
ADC10CTL0 |= ENC + ADC10SC; // Sampling and conversion start
__bis_SR_register(CPUOFF + GIE); // LPM0, ADC10_ISR will force exit

if((THRESHOLD3+0x003E) >= ADC10MEM && ADC10MEM > (THRESHOLD3-hystyrisis) & TACCR1>=TIM1)
{

CCR1 -= VAR;

_delay_cycles(350000);

}

else if((THRESHOLD2+hystyrisis) >= ADC10MEM && ADC10MEM > (THRESHOLD2-hystyrisis) & TACCR1<=TIM2)
{
CCR1 += VAR;

_delay_cycles(350000);

}
else if((THRESHOLD1+hystyrisis) >= ADC10MEM && ADC10MEM > (THRESHOLD1-hystyrisis) & TACCR2>=TIM1)
{
CCR2 -= VAR;

_delay_cycles(350000);

}
else if((THRESHOLD0+hystyrisis) >= ADC10MEM & TACCR2<=TIM2)
{
CCR2 += VAR;

_delay_cycles(350000);

}
else
{
_delay_cycles(0);
}

}}

// ADC10 interrupt service routine
#pragma vector=ADC10_VECTOR
__interrupt void ADC10_ISR(void)
{
_delay_cycles(1);
__bic_SR_register_on_exit(CPUOFF); // Clear CPUOFF bit from 0(SR)
}
// Timer_A3 Interrupt Vector (TA0IV) handler
#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector=TIMER0_A1_VECTOR
__interrupt void Timer_A(void)
#elif defined(__GNUC__)
void __attribute__ ((interrupt(TIMER0_A1_VECTOR))) Timer_A (void)
#else
#error Compiler not supported!
#endif
{
switch( TA0IV )
{
case 2: // CCR1
{
P2OUT ^= 0x06; // Toggle P1.0
}
break;
case 4:
{
P2OUT ^= 0x09; // Toggle P1.
}
break;

case 10: break; // overflow not used
}}

NEENA JOSEPH said:

I am not toggling LED.

This looks like you toggle the output:

P2OUT ^= 0x06; // Toggle P1.0

But you also have

CCTL1 = CCIE + OUTMOD_7; // CCR1 interrupt enabled

the OUTMOD_7 in your code, although I cannot see any PxSEL settings to assign a pin to that functionality.

NEENA JOSEPH said:

P2OUT ^= 0x06;

NEENA JOSEPH said:

// Toggle P1.0

NEENA JOSEPH said:

this is four selecting output led arrays.In this command we are selecting 2nd and 3rd LED array.

The above three quotes from you are talking about three different subjects. Are they not?