Best Way to Keep Track of Time with the nRF52

[A Knecht]

I need to keep track of time on a device featuring the nRF52 and have an RTC run continuously in the background. The drift should not be more than a few seconds over a year. Is this possible to achieve with a moderate power consumption?

I am a bit overwhelmed with the number of of ways to keep track of time in the SDK:

• app_timer*
• Also, the changes to app_timer posted in this forum by Clem Taylor. This dates back to 2015, though and targets the nRF51?
• app_simple_timer*
• nrf_drv_timer*
• nrf_drv_rtc*
• nrf_drv_clock*

Is there anything that comprehensively explains the difference between these? Also, what should my approach be to get a system clock with as little time drift as possible?

[Sigurd]

Hi,

The clock control system is basically the system that drives the whole chip, including the CPU and all peripherals. It can be divided into 2 clock systems, the low frequency clock(LFCLK) and the high frequency clock (HFCLK) . With nrf_drv_clock* you have several ways to interact with the clocks, including initialization and calibrating.

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The nrf_drv_rtc* includes drivers for the Real-time counter (RTC) peripheral.

The nrf_drv_timer* includes drivers for the TIMER peripheral.

The main difference between TIMER and RTC (Real-time counter) is that:

• TIMER uses the high-frequency clock source (HFCLK, 16 MHz), which means better resolution (62.5 ns) and higher power consumption (typ. 5 or 70 uA depending on HFCLK source).

• RTC uses the low-frequency clock source (LFCLK, 32 KHz), which means less resolution (~30 us) and lower power consumption (typ. 0.1 uA).

The app_timer* and app_simple_timer* are libraries that builds on top the RTC1 peripheral(app_timer) and the TIMER1 peripheral(app_simple_timer). This gives more high-level functionality where you can create multiple timer instances, and you have functions to start and stop the timers. Take a look at the Application Timer Tutorial if you want to learn more.

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For keeping track of time on the nRF52, I would recommend taking a look at the nrf-calendar-example we have on Github.

[sonalkale]

hello,

how nrf-calendar-example work?

I can create hex file using sdk14.But there is no output using printf command on uart port.

please suggest some solution.

Thank You.

[Sigurd]

Note that the example was originally written for SDK 13, so you might want to use that to test the example.

I recommend using PuTTY to test the example.

With PuTTY serial connection it should look like this: