RTC Timer

Cryptik · **Posted:** Thu Aug 16, 2012 3:24 pm

I have an interesting issue with the waspmote. I can set an RTC interrupt time for 1 minute using the standard code for setting alarm 1 using an offset. I use RTC_ALM1_MODE4 and set the string to "00:00:01:00". I put the mote into deep sleep and then it gets turned back on by the RTC in one minute increments.

All seems to be working... except that after about 75 of these one minute cycles, the sleep time begins to increase. I have also set an ACC interrupt so that if either the time limit or the device is moved...it will wake up and send a zigbee packet. What I noticed is that the sleep time extends so much that it will eventually stop waking up. The odd thing is that if I let it run for about 5 hours... it will stop waking up on the RTC, but if I move the device...the ACC interrupt will work. The device then wakes up and goes back to one minute sleep cycles.

Is there something that I have set wrong?

Kind regards
Cryptik

libelium-dev · **Joined:** Mon Sep 28, 2009 1:06 pm **Posts:** 7815

Hi Cryptik,

that sounds like you are missing interruptions from the RTC, could you please check the voltage of the button cell?

Regards.

Cryptik · **Posted:** Fri Aug 17, 2012 4:31 pm

thank you libelium-dev. The voltage was 0.5 so it was certainly the problem. I switched out the battery and I am running the tests again.

Kind regards,
Cryptik

libelium-dev · **Joined:** Mon Sep 28, 2009 1:06 pm **Posts:** 7815

Cryptik,

Glad to hear you solve your issue.

Regards

Cryptik · **Posted:** Tue Aug 21, 2012 4:44 am

So.. after some research and experimenting... I found it does not appear it was only the battery. I was having issues with one of the motes. After about 10 minutes (sometimes an hour or two) the mote would simply stop waking up on the one minute RTC interrupts.

Checking the battery should that it was indeed low on voltage. I replaced it with a new battery that tested out around 3V and the same thing continued to happen. I figured it was my code...maybe a memory overrun. After working with the code to optimize...the problem just would not go away.

As a last ditch effort, I switched to another mote and loaded the code to that device. The code has been running for about 12 hours with no problems.

Is is possible that the RTC is damaged on the mote? Is there a software reason that it would behave this way?

Kind regards,
Cryptik

libelium-dev · **Joined:** Mon Sep 28, 2009 1:06 pm **Posts:** 7815

Cryptik,

The most probably cause for your issue is that coin cell battery is quite discharged. This is not normal, and coin cell can last for years. Check coin cell voltage to be sure.

Regards.