MSP430FR59941: configure LFXO

John Moore39

Expert 1470 points

Part Number: MSP430FR59941

Dear Sirs:

I'm having trouble configuring the LFXO (32khz crystal) for use with timer A1. Do you have an example or procedure.

I'm setting:

PJSEL0 |= BIT4; //enable LFXO LFXO
PJSEL1 &= ~BIT4;
PJSEL0 |= BIT5;
PJSEL1 &= ~BIT5;

// Configure timer A1:

void ConfigTimerA1(void)

{

TA1CTL |= 0x0100; // TASSEL_1=Use ACLK as source for timer

TA1CTL |= MC_1; //Use UP mode timer continuous

TA1CCR0 = 0xffff; //start
}

Thanks,

John

over 3 years ago

0 Bruce McKenney47378 over 3 years ago

Guru 88510 points

What sort of trouble are you having?

The sequence appears in Example msp430fr599x_cs03.c, here:

http://dev.ti.com/tirex/explore/node?node=AFwRLGNEiJiAjRrZ2osowA__IOGqZri__LATEST

I suspect you can just copy/paste it (that's what I do).

0 John Moore39 over 3 years ago in reply to Bruce McKenney47378

Expert 1470 points

Thanks, Bruce:

I’m needing a higher clock frequency than 10khz to clock the timer. Using the timer to measure pulse widths.

I’ve tried everything to make ACLK use the LFXO as input to the timer.

But ACLK keeps coming up 10khz.

It would probably work as well using MODCLK for ACLK but can't get it either!

John

0 Bruce McKenney47378 over 3 years ago in reply to John Moore39

Guru 88510 points

Did you try copy/pasting the LFXT startup sequence from that Example I llinked to? That's what I do.

0 John Moore39 over 3 years ago in reply to John Moore39

Expert 1470 points

Thanks, Bruce:

Believe it is working. You won't believe what I was doing.

I was using another timer (also driven from ACLK). The other timer was timing out every .01 sec. So naturally

no matter what the (common) clock source was, the time difference in the second timer came up exactly 100.

Clever no?

John

0 John Moore39 over 3 years ago in reply to John Moore39

Expert 1470 points

Thanks for your help, Bruce:

I looked over the example and changed mine to match. Then started looking at the problem through your eyes.

It was then that I realized I could be making a fundamental mistake.

Anyway Thanks

John

**Attention** This is a public forum

MSP low-power microcontrollers

MSP low-power microcontroller forum

MSP430FR59941: configure LFXO