TimeStamp in nRF52832

RE: TimeStamp in nRF52832

Einar Thorsrud — Wed, 18 Mar 2020 12:44:11 GMT

Hi,

[quote user="Sunil vignesh"]will you suggest any external ic for Timestamp.[/quote]

I do not have any suggestions for that. It is not directly related to the nRF, but perhaps some other members on this forum has some suggestions?

[quote user="Sunil vignesh"]how nrf_calender works.[/quote]

nrf_calendar uses the RTC to generate ticks and the time.h library to map this to actual calendar time and date. You can refer to the source code for details.

[quote user="Sunil vignesh"]how the time and date will taken[/quote]

The calendar time and date is calculated in SW, based on the elapsed time, counted by the RTC.

RE: TimeStamp in nRF52832

Sunil vignesh — Wed, 18 Mar 2020 09:55:53 GMT

will you suggest any external ic for Timestamp.

how nrf_calender works.

how the time and date will taken

RE: TimeStamp in nRF52832

Einar Thorsrud — Mon, 16 Mar 2020 06:49:21 GMT

The RTC will work in normal low power (system ON) sleep mode, yes. It is always used when you use BLE for instance, in order to wake up at connection events, advertising events etc. The current consumption is system ON low power mode is ~2-3 uA, which is not very much.

It will not run in system off mode, though, but most applications never use system off. In system off the IC is almost entirely powered off, and can only wake up on GPIO, LPCOMP or NFC.

RE: TimeStamp in nRF52832

Sunil vignesh — Mon, 16 Mar 2020 06:44:18 GMT

will timer / counter work in sleep mode?

RE: TimeStamp in nRF52832

Einar Thorsrud — Wed, 11 Mar 2020 08:23:03 GMT

Hi,

[quote user="Sunil vignesh"]internal RTC is a counter right?[/quote]

Yes, the RTC is a counter that can count 32.768 kHz clock cycles, which may or may not be divided by a Prescaler. (So the accuracy of the RTC is given by the accuracy of your 32 kHz clock source.)

[quote user="Sunil vignesh"]i have to count the time until reset or power off. When it again power up the data will be lost right?[/quote]

In principle yes, though you could use a method such as suggested by hmolesworth, which seems like a very good suggestion.

RE: TimeStamp in nRF52832

hmolesworth — Tue, 10 Mar 2020 16:06:58 GMT

A tip is to keep the current time value in RAM memory that is not initialised on a reset. On a cold start reset where the RAM does not contain a valid RTC value then the time value would be set to zero and a companion value set to some fixed constant; this latter fixed constant can subsequently be used following a reset to indicate validity of the RTC time. This allows the RTC to continue with only time lost while the reset takes place. This is sample code for both SES and IAR:

// Segger Embedded Studio format
// Place following data in section .noinit so it doesn't get wiped on a reset
  static volatile uint32_t mIamInitialisedRTC __attribute__((section(".non_init"))); // Valid data indication for this data
  // 32-bit unsigned RTC time
  static volatile uint32_t mRTC_Timer         __attribute__((section(".non_init")));
// End - Place following data in section .noinit so it doesn't get wiped on a reset

// IAR Format:
// Place following data in section .noinit so it doesn't get wiped on a reset
#pragma default_variable_attributes = @ ".noinit"
  static volatile uint32_t mIamInitialisedRTC; // Valid data indication for this data
  // 32-bit unsigned RTC time
  static volatile uint32_t mRTC_Timer;
#pragma default_variable_attributes =
// End - Place following data in section .noinit so it doesn't get wiped on a reset

Care has to be taken over the type of reset and applicable errata, since there are conditions that can corrupt RAM. The RAM area for segment .noinit also has to have power enabled regardless of operating mode (eg in system Off).

In practice this works well; resets are rare (ideally only happen once when battery first installed) and only have minimal impact on RTC time.

RE: TimeStamp in nRF52832

Sunil vignesh — Tue, 10 Mar 2020 14:50:26 GMT

Here SW, are mentioning flash storage ?

internal RTC is a counter right? . i have to count the time until reset or power off. When it again power up the data will be lost right?

i will refer that example

RE: TimeStamp in nRF52832

Einar Thorsrud — Tue, 10 Mar 2020 13:59:42 GMT

I see. If you are happy with the risk of getting an incorrect timestamp in case of a reset, then you can use the internal RTC (perhaps using the app timer library and a repeated timer to update your timekeeping SW). We do not have any official examples for that, but you can refer to nrf-calendar-example.

RE: TimeStamp in nRF52832

Sunil vignesh — Tue, 10 Mar 2020 13:36:38 GMT

My case is . I need to read the sensor data and through value to the mobile app. device has to connect the mobile phone daily. and mobile app it send data to server. there it will have date time respective sensor data .

but if the device not connected to mobile for two days . the sensor data will be stored in external EEPROM / FLASH but i need to send timestamp . to match the database.

Can you give solution for that

RE: TimeStamp in nRF52832

Einar Thorsrud — Tue, 10 Mar 2020 12:26:00 GMT

Hi,

You can use the RTC peripheral in the nRF to keep time, but remember that the RTC will be reset when the chip is reset for any reason. Also, there is no HW for mapping the RTC ticks to time and date, so you need to keep the calendar in SW. If this is not acceptable, then you need to use an external dedicated RTC chip.