msp430G2553: P2.6

Justin Mooney

Part Number: MSP430G2553

Hi!

I am trying to create a PWM signal, and it works for the P1.6 (LED2) output, but it is not working for the P2.6 pin. Could someone please help me?

Thanks!

Here's my code:

#include <msp430.h>

void main(void)
{
WDTCTL = WDTPW + WDTHOLD; // Stop WDT
ConfigureClockModule();

P1DIR |= BIT6; // P1.6 as output
P2DIR |= BIT6; // P2.6 as output

P1SEL |= BIT6; // P1.6 select as output
P2SEL &= ~BIT6; // Clearing SEL bit
P2SEL2 &= ~BIT6; // Clearing SEL2 bit

TA0CCR0 = 999; // PWM Period = TA0CCR0 +1
TA0CCTL1 = OUTMOD_7; // CCR1 reset/set

TA0CCR1 = 250; // CCR1 PWM duty cycle = TA0CCR1*100/(TA0CCR0+1)
TA0CCTL2 = OUTMOD_7; // CCR2 reset/set

TA0CCR2 = 250; // CCR2 PWM duty cycle = TA0CCR2*100/(TA0CCR0+1)
TA0CTL = TASSEL_2 + MC_1 + TACLR; // SMCLK, up mode, clear TAR

__bis_SR_register(LPM0_bits); // Enter LPM0
__no_operation(); // For debugger
}

over 8 years ago

0 Clemens Ladisch over 8 years ago

Guru 324950 points

P1SEL |= BIT6; // P1.6 select as output

This is the correct method to connect the TA0.1 output to P1.6.

P2SEL &= ~BIT6; // Clearing SEL bit
P2SEL2 &= ~BIT6; // Clearing SEL2 bit

This is not the correct method to connect the TA0.1 output to P2.6. See table 21 of the datasheet.

And the TA0.2 output is available only at P3.0 or P3.6.

0 Justin Mooney over 8 years ago in reply to Clemens Ladisch

Prodigy 100 points

So here is table 21, and that's what I used to P2SEL = 0 and P2SEL2 = 0. Is that not correct?

0 Clemens Ladisch over 8 years ago in reply to Justin Mooney

Guru 324950 points

To get a PWM signal out of the pin, you have to connect a timer's output to it.

"TA0.1" is such a timer output. "P2.6" means that the pin is controlled by software.

0 Justin Mooney over 8 years ago in reply to Clemens Ladisch

Prodigy 100 points

So then I would set P2DIR = BIT6, P2SEL = BIT6, and P2SEL2 = ~BIT6?

0 Jeff Hastings over 8 years ago in reply to Justin Mooney

Intellectual 820 points

it is best to not change bits in PxDIR or PxSELx reisters that you don't care about.
try this code snip:

// general setup for '2553 for having PWM on P2.6
// set pin for output and
// attach it to timer A0 output 1
P2DIR |= BIT6;
// in P2SEL, set bit 6 and clear bit 7
P2SEL |= BIT6;
P2SEL &= ~BIT7;
// in P2SEL2, clear bit 6 and bit 7
P2SEL2 &= ~(BIT6 | BIT7)

0 Justin Mooney over 8 years ago in reply to Jeff Hastings

Prodigy 100 points

Hi Jeff,

Thank you for your help! May I ask why you clear BIT7 even though I won't be using it?

Thanks!

0 Jeff Hastings over 8 years ago in reply to Justin Mooney

Intellectual 820 points

see table 21 of SLAS735J.
said table would perhaps be better/clearer if the column heading P2DIR.x read P2DIR.6 instead. oh well

here's what going on.. as I understand it. XIN and XOUT pins function as a pair, normally; hanging a 32.6768 khz crystal on them is quite common. if you're using the internal DCO and want to use the "xin" pin as an output, than it makes sense to specifically detach "xout" pin from external crystal-related functions. keeping P2SEL.7 and P2SEL2.7 bits clear does this.

0 Justin Mooney over 8 years ago in reply to Jeff Hastings

Prodigy 100 points

Ohhh I see! Thank you so much, Jeff! It works perfectly now!

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msp430G2553: P2.6