RTC Time Discrepancy Issue with nRF5340

RE: RTC Time Discrepancy Issue with nRF5340

Sigurd — Tue, 03 Sep 2024 11:59:57 GMT

Hi!

Instead of using the RTC(real time counter peripheral) directly like that, you could try using e.g. the RTC emulated device driver instead.

https://docs.zephyrproject.org/latest/hardware/peripherals/rtc.html#rtc-emulated-device

https://github.com/nrfconnect/sdk-zephyr/blob/main/drivers/rtc/rtc_emul.c

RE: RTC Time Discrepancy Issue with nRF5340

Krishnachandran_a — Tue, 03 Sep 2024 03:51:40 GMT

Hi Sigurd,

Thank you for the update. The problem is that, although we updated RTC via the mobile app (using BLE) without any problems, there was a noticeable difference in RTC after around 30 minutes of operation (slow).

For your reference, the RTC init and call back code are attached. Please review and share any recommendations.

void rtc_init()
{

	const nrfx_rtc_config_t config = {
		.prescaler = NRF_RTC_FREQ_TO_PRESCALER(RTC_PRESCALAR), 
		.interrupt_priority = NRFX_RTC_DEFAULT_CONFIG_IRQ_PRIORITY,
		.tick_latency = NRFX_RTC_US_TO_TICKS(2000, 32768),
		.reliable = true};
		
	// Function for initializing the RTC driver instance.
	nrfx_rtc_init(&rtc_driver_instance_0, &config, rtc_callback);

	IRQ_DIRECT_CONNECT(RTC0_IRQn, 0, nrfx_rtc_0_irq_handler, 0);

	// Function for disabling the TICK event.
	nrfx_rtc_tick_disable(&rtc_driver_instance_0);
	
	nrfx_rtc_tick_enable(&rtc_driver_instance_0,true);

}

void rtc_callback(nrfx_rtc_int_type_t val)
{
	nrfx_rtc_counter_clear(&rtc_driver_instance_0);
	// Enable interupt
	nrfx_rtc_int_enable(&rtc_driver_instance_0, 131072);
	update_time(val);

    if(read_rtc_state == true && val == 4)
    {
        read_rtc_count++;
        if(read_rtc_count >= 100)
        {
            read_rtc_count = 0;
            rtc_read_callback_function();
        }
    }
    else if(read_rtc_state  == false && read_rtc_count != 0)
    {
        read_rtc_count =0;
    }
}

Regards,

Krishna Chandran

RE: RTC Time Discrepancy Issue with nRF5340

Sigurd — Mon, 02 Sep 2024 13:27:41 GMT

Depending on e.g. BLE connection interval, BLE connection Slave Latency, etc, there will be a bit delay from the time mobile phone sends the data, to it's received on the nRF, and you update the RTC. You could try requesting a lower connection interval when updating, and see if that improves things.

RE: RTC Time Discrepancy Issue with nRF5340

Krishnachandran_a — Sun, 01 Sep 2024 09:52:49 GMT

Hi,

[quote userid="15146" url="~/f/nordic-q-a/114354/rtc-time-discrepancy-issue-with-nrf5340/500591"]Could you explain a bit more on how you do this sync? [/quote]

Actually we are using a mobile app, using app(BLE)we are updating the time to device.

[quote userid="15146" url="~/f/nordic-q-a/114354/rtc-time-discrepancy-issue-with-nrf5340/500591"]How do you get the "actual time" ?[/quote]

Actual time means the system time.

Regards,

Krishnachandran

RE: RTC Time Discrepancy Issue with nRF5340

Sigurd — Fri, 30 Aug 2024 12:36:21 GMT

Hi!

Could you explain a bit more on how you do this sync? How do you get the "actual time" ?