CC430 RTC interrupts in calendar mode

Daniel Berenguer

Other Parts Discussed in Thread: CC430F5137

I've been using RTC interrupts in counter mode on my CC430F5137 platform without any issue. Now I want to explore the calendar capabilities of this MCU but this seems to be a far more complex task. Below is a piece of code used to set current time and a basic alarm that should be triggered every hour at 25 minutes.

RTC_SET_ACLK_XT1(); // Connect ACLK to 32.768 KHz crystal
WDTCTL = WDTPW | WDTHOLD;               // Stop WTD

// Configure RTC
RTCCTL01 |= RTCMODE | RTCTEVIE | RTCAIE | RTCRDYIE; 
RTCCTL01 |= RTCHOLD; // RTC hold

// Set current time
RTCYEAR = 2015;
RTCMON = 4;
RTCDAY = 7;
RTCDOW = 2
RTCHOUR = 17;
RTCMIN = 22
RTCSEC = 0;

// Trigger alarm every hour at 25 minutes
RTCAMIN = 25 & 0x80; // RTC Minute Alarm and enable

// Start RTC calendar mode
RTCCTL01 &= ~(RTCHOLD);

// Enter LPM3 with interrupts
__bis_SR_register(LPM3_bits + GIE);

// The LED should turn on at 17:25:00
LED_ON();

As you may guess, the LED is never turned on with the above code. There is no example about the use of CC430's RTC in calendar mode so I've been looking around for other examples without much luck.

Has anyone experience with this mode on any CC430 platform?

Thanks in advance for your time.

over 10 years ago

0 Daniel Berenguer over 10 years ago

Expert 2185 points

There is a typo in my post. RTCAMIN needs to be ORed against 0x80 and not ANDed:

// Trigger alarm every hour at 25 minutes
RTCAMIN = 25 | 0x80; // RTC Minute Alarm and enable

The correct code was in fact the one used in my tests.

0 Daniel Berenguer over 10 years ago in reply to Daniel Berenguer

Expert 2185 points

I found the problem.

The initialization of RTCCTL0/RTCCTL1 needs to be this one:

RTCCTL01 |= RTCMODE | RTCAIE | RTCHOLD;

0 Katie Pier over 10 years ago in reply to Daniel Berenguer

TI__Guru* 80381 points

Hi Daniel,

So glad to hear that you figured it out, and thanks for sharing the solution in case others run into the same issue in the future.

Now, was the issue that you had the other RTC interrupts enabled, and this caused a problem in your ISR? It's a little hard to understand your problem/solution without seeing the ISR code.

Regards,
Katie

0 Daniel Berenguer over 10 years ago in reply to Katie Pier

Expert 2185 points

My ISR code is quite simple; it just takes the MCU out of LPM:

__attribute__((interrupt(RTC_VECTOR)))
void rtcISR(void)
{
  __bic_SR_register_on_exit(LPM3_bits);  // clears the bits corresponding to LPM3 and exits the low power mode
}

With the above code RTCRDYIE seems to be triggering an interrupt almost immediately after starting the RTC module so the MCU was exiting from LPM very quickly. I'm now reading RTCIV in order to avoid this misunderstandings.

0 Katie Pier over 10 years ago in reply to Daniel Berenguer

TI__Guru* 80381 points

Perfect! That makes sense. Thanks for the further explanation. :-)

0 Dipankar panda over 9 years ago in reply to Daniel Berenguer

Prodigy 180 points

Thanks for this post Daniel Berenguer . I was also making mistake in setting up this line. Actually forgot to set AE bit of RTCAMIN register. your post was helpful.

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CC430 RTC interrupts in calendar mode