7us Pulse width with MSP430G2452 Launchpad

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jamdaman5000
Posts: 2
Joined: Thu Sep 08, 2011 7:08 pm

7us Pulse width with MSP430G2452 Launchpad

Post by jamdaman5000 » Thu Sep 08, 2011 7:18 pm

Hello everyone!

I have a challange for all of you MSP pro's out there. I want to make a PWM of sorts with a 7us pulse width, and a 2.77ms period. Here's the catch, I need to vary/skip pulses. The "MU" arrays below indicate a 1 when I want a 7us pulse, and a 0 when I skip that pulse.

I am using an MSP430G2452 on a TI launchpad development board. I am a PIC guy, so I am not quite familiar with TI's MSP430 registers. I've been working for hours at this and can't quite seem to get it. Here's what I have so far, feel free to markup/dissect/question any parts of my code :D

-Jameson


#include <MSP430G2452.h>

void ConfigClocks(void);
void ConfigTimerA0(void);

unsigned int PULSE_WIDTH = 20; //60Mu/min pulse is 7us @1MHz, that is 7 counts on timer A2
unsigned int DEAD_TIME = 44208; //dead time after pulse makes 2.77ms
unsigned int MU_80[6] = {1, 0, 0, 0, 0, 0}; //60Mu/min pulse is 7us @8mHz, that is 56 counts on timer A2
unsigned int MU_160[6] = {1, 0, 0, 1, 0, 0};
unsigned int MU_240[6] = {1, 0, 1, 0, 1, 0};
unsigned int MU_320[6] = {1, 1, 0, 1, 1, 0};
unsigned int MU_400[6] = {1, 1, 1, 1, 1, 0};
unsigned int CYCLE_STATE = 0; //to remember which part of the pulse train we are on.
unsigned int BEAM_ON = 0;


void main(void)
{
WDTCTL = WDTPW + WDTHOLD; //stop watchdog timer
P1DIR = BIT0; //P1.0 output
P1OUT = 0;
ConfigClocks();
ConfigTimerA0();
_BIS_SR(GIE); //TURN ON INTERRUPTS!!!!


while(1)
{
_NOP();
}
}


void ConfigClocks(void)
{
if(CALBC1_16MHZ == 0xFF || CALDCO_16MHZ == 0xFF)
{
P1OUT = 1;
while(1);
}
BCSCTL1 |= CALBC1_16MHZ; //use 1MHZ calibrated dco
DCOCTL |= CALDCO_16MHZ;
IFG1 &= ~OFIFG;
BCSCTL2 &= ~SELS;
BCSCTL2 |= DIVS0;
}

void ConfigTimerA0(void)
{
CCTL0 = OUTMOD_7 + CCIE;
CCR0 = DEAD_TIME;
TACTL = TASSEL_2 + MC_1 + TAIE;
}

#pragma vector=TIMER0_A0_VECTOR
__interrupt void Timer_A0 (void)
{

if(MU_400[CYCLE_STATE] == 1)
{
P1OUT |= BIT0; //led on
CCR1 = PULSE_WIDTH;
}
else
{
P1OUT &= ~BIT0; //led off
CCR1 = 0;
}
CCTL0 &= ~CCIFG;

if(CYCLE_STATE == 5)
{
CYCLE_STATE = 0;
}
else
{
CYCLE_STATE += 1;
}


}

jamdaman5000
Posts: 2
Joined: Thu Sep 08, 2011 7:08 pm

Re: 7us Pulse width with MSP430G2452 Launchpad

Post by jamdaman5000 » Fri Sep 09, 2011 12:02 pm

So I got the pulses working properly (well...with 10us pulses instead of 7).

Now I would like to incorporate this into the capacitive touch code.

Any suggestions? Here's my pulse code working below:


#include <MSP430G2452.h>

void ConfigClocks(void);
void ConfigTimerA0(void);

unsigned int PULSE_WIDTH = 111; //60Mu/min pulse is 7us @1MHz, that is 7 counts on timer A2
unsigned int OFF_TIME = 26625; //dead time after pulse makes 2.77ms
unsigned int CYCLE = 26736;
unsigned int MU_80[6] = {1, 0, 0, 0, 0, 0}; //60Mu/min pulse is 7us @8mHz, that is 56 counts on timer A2
unsigned int MU_160[6] = {1, 0, 0, 1, 0, 0};
unsigned int MU_240[6] = {1, 0, 1, 0, 1, 0};
unsigned int MU_320[6] = {1, 1, 0, 1, 1, 0};
unsigned int MU_400[6] = {1, 1, 1, 1, 1, 0};
unsigned int CYCLE_STATE = 0; //to remember which part of the pulse train we are on.
unsigned int BEAM_ON = 0;
unsigned int waitFlag = 0;


void main(void)
{
WDTCTL = WDTPW + WDTHOLD; //stop watchdog timer
P1DIR = BIT0; //P1.0 output
P1OUT = 0;
if(CALBC1_16MHZ == 0xFF || CALDCO_16MHZ == 0xFF)
{
P1OUT = 1;
while(1);
}
ConfigTimerA0();
_BIS_SR(GIE); //TURN ON INTERRUPTS!!!!
ConfigClocks();

}


void ConfigClocks(void)
{
BCSCTL1 |= CALBC1_16MHZ; //use 1MHZ calibrated dco
DCOCTL |= CALDCO_16MHZ;
IFG1 &= ~OFIFG;
BCSCTL2 &= ~SELS;
BCSCTL2 |= DIVS0;
}

void ConfigTimerA0(void)
{
CCTL0 = OUTMOD_5 + CCIE;
CCR0 = OFF_TIME;
CCR1 = PULSE_WIDTH;
TACTL = TASSEL_2 + MC_1 + TAIFG;
}

#pragma vector=TIMER0_A0_VECTOR
__interrupt void Timer_A0 (void)
{
if(waitFlag == 1)
{
CCR0 = OFF_TIME; //let the rest of the period remain off
P1OUT &= ~BIT0;
waitFlag = 0;
}
else
{

if(MU_240[CYCLE_STATE] == 1)
{
P1OUT |= BIT0; //led on
CCR0 = PULSE_WIDTH;
waitFlag = 1;
}
else
{
P1OUT &= ~BIT0; //led off
CCR0 = CYCLE;
}

CYCLE_STATE = CYCLE_STATE + 1; //increment cycle state
if(CYCLE_STATE == 6)
{
CYCLE_STATE = 0;
}

}
}

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