Problem in understanding RTC

RE: Problem in understanding RTC

Ole Bauck — Fri, 08 Jan 2016 11:37:22 GMT

I would definitely guess so. Using normal timer would make i.e. the HRM example use a lot of power. Since we from nordic didn't write this library, I cannot tell for sure. If you have questions about the arduino library I would ask redbearlabs.

RE: Problem in understanding RTC

adrianwong — Fri, 08 Jan 2016 04:52:52 GMT

Ya if i try using the code found on github, I will be getting error complaining about multiple definitions of void RTC_IRQHandler(void). Yes the ticker class is working, but it is using low power RTC? My aim is to use RTC to saving power instead of normal timer.

RE: Problem in understanding RTC

Ole Bauck — Thu, 07 Jan 2016 15:30:43 GMT

You can use the Ticker class like is shown in the HRM example, with something like ticker_task2.attach_us(callback_function, 100). I have not tested it though to see if it actually fires every 100us. You can also try to use the code found on github, but I guess you will get a compile error complaining about multiple definitions of void RTC_IRQHandler(void).

RE: Problem in understanding RTC

adrianwong — Thu, 07 Jan 2016 02:55:41 GMT

Yes i'm using redbear nrf51822-arduino library in my our PCB.

RE: Problem in understanding RTC

Ole Bauck — Wed, 06 Jan 2016 11:53:13 GMT

Is this the redbearlab module (i.e. BLE nano)? I am not too familiar with programming the nRF51 from Arduino IDE.

RE: Problem in understanding RTC

adrianwong — Wed, 06 Jan 2016 11:37:57 GMT

Okay. I try to find the library that can use together with Arduino IDE but I couldn't find

RE: Problem in understanding RTC

Ole Bauck — Wed, 06 Jan 2016 11:25:48 GMT

app_timer is a SDK module/library that use RTC to schedule multiple tasks regulary.

RE: Problem in understanding RTC

adrianwong — Wed, 06 Jan 2016 10:26:06 GMT

what is the different of app_timer and RTC?

RE: Problem in understanding RTC

Ole Bauck — Wed, 06 Jan 2016 10:20:24 GMT

No, I guess you are using some SDK modules that are using app_timer, then you have no RTC left to use (SD uses RTC0 and there are only two RTC on nRF51). You could use app_timer, but the minimum time between two events is 5 ticks (152.59us with prescaler 0) as stated here. Here is a tutorial on using app_timer.

RE: Problem in understanding RTC

adrianwong — Wed, 06 Jan 2016 09:43:32 GMT

Ok. If another library that i using now is already used RTC1 then i cannot used again right? It will show me error like "multiple definition of RTC1_IRQHandler".

RE: Problem in understanding RTC

Ole Bauck — Wed, 06 Jan 2016 09:36:18 GMT

You cannot get 100us accurately. Since the resolution of the RTC with prescaler 0 is 30.517us, the closest number would be 91.55us. To get 100us accurately, you have to use the TIMER peripheral that is able to run at 16MHz, however this will draw a lot more power (~250uA+ from crystal). To change to RTC1 susbstitute RTC0 by RTC1.

RE: Problem in understanding RTC

adrianwong — Wed, 06 Jan 2016 04:11:59 GMT

Thanks Ole Bauck. What is the best way for me to set the timer to 100us accurately? By the way, If i wanted to change from RTC0 to RTC1 i just need to substitute all RTC0 to RTC1 only right?

RE: Problem in understanding RTC

Ole Bauck — Tue, 05 Jan 2016 12:37:26 GMT

And NRF_RTC0->CC[0] = NRF_RTC0->COUNTER + 32768; in the interrupt as the RTC is not reset unless it overflows.

RE: Problem in understanding RTC

adrianwong — Tue, 05 Jan 2016 12:12:37 GMT

What you mean is by putting NRF_RTC0->CC[0] = 32768 when NRF_RTC0->PRESCALER = 0 then the IRQ handler will trigger every 1s right? Nope, this is not working.

RE: Problem in understanding RTC

Ole Bauck — Tue, 05 Jan 2016 12:04:56 GMT

With prescaler 0, the RTC will run at 32.768 KHz which means 32768 counts per second. This means that the CC[0] needs to be initialized and incremented with 32768 instead of 1000. I suggest that you read the Reference Manual chapter about RTC to get a better understanding of how it works.

RE: Problem in understanding RTC

adrianwong — Tue, 05 Jan 2016 10:47:13 GMT

From the code itself, how can i change the RTC interval to 1s? THrough my calculation i couldn't get what i want. Kindly assist.

RE: Problem in understanding RTC

awneil — Mon, 04 Jan 2016 12:20:28 GMT

The comments in the code look pretty detailed already.

RE: Problem in understanding RTC

adrianwong — Mon, 04 Jan 2016 10:18:17 GMT

Hi , what i need is can you put details comments beside the every line of the code that i sent. Then from there i can slowly figure out what is actually happen in the code. Thanks. By the way, plus what kind of output can i expect? Currently, the code running and displayed "4, 2 , 1, 1, 1, 1, 1, 1, 1, 1, 1" by checking through serial terminal. Then it stop forever.

RE: Problem in understanding RTC

awneil — Mon, 04 Jan 2016 09:47:35 GMT

Indeed - it is difficult to assist when it's not clear what assistance you require!

You say you are "a newbie in nordic" - do you have any prior programming experience at all? Do you have any prior experience with microcontrollers?

RE: Problem in understanding RTC

atune — Mon, 04 Jan 2016 09:43:58 GMT

It'd be helpful to yourself and anyone responding if you could be more specific about what exactly is difficult to understand. There are only a few registers used and the product datasheet should explain most of the things sufficiently well.