RE: ds3231 RTC changes the internal clock frequency in nrf52840

Osse — Thu, 21 Apr 2022 12:53:53 GMT

CONFIG_SYS_CLOCK_TICKS_PER_SEC is set to 32768 in autoconfig.h

RE: ds3231 RTC changes the internal clock frequency in nrf52840

qwertynoon — Thu, 21 Apr 2022 09:50:56 GMT

You have to know how much tics do you have at 1 second

This value should be your reference

LOG_INF("CONFIG_SYS_CLOCK_TICKS_PER_SEC = %d", CONFIG_SYS_CLOCK_TICKS_PER_SEC);

RE: ds3231 RTC changes the internal clock frequency in nrf52840

Osse — Thu, 21 Apr 2022 08:22:33 GMT

We get this same issue with the sampe "Maxim DS3231 TCXO RTC Sample Application"

https://developer.nordicsemi.com/nRF_Connect_SDK/doc/1.8.0/zephyr/samples/drivers/counter/maxim_ds3231/README.html

We modified the function set_aligned_clock a bit, to write to the terminal before and after the call on "k_sleep(K_msec(10000));". We print t2 - t1, this seems correct, 327690 ticks, but measuring with a stop watch it took 95 seconds. Almost 10 times 10 000msec. Mind you this is the only change we made to the sample. We use the same overlay file.

The changes to the function:

static void set_aligned_clock(const struct device *ds3231)
{
	if (!IS_ENABLED(CONFIG_APP_SET_ALIGNED_CLOCK)) {
		return;
	}

	uint32_t syncclock_Hz = maxim_ds3231_syncclock_frequency(ds3231);
	uint32_t syncclock = maxim_ds3231_read_syncclock(ds3231);
	uint32_t now = 0;
	int rc = counter_get_value(ds3231, &now);
	uint32_t align_hour = now + 3600 - (now % 3600);

	struct maxim_ds3231_syncpoint sp = {
		.rtc = {
			.tv_sec = align_hour,
			.tv_nsec = (uint64_t)NSEC_PER_SEC * syncclock / syncclock_Hz,
		},
		.syncclock = syncclock,
	};

	struct k_poll_signal ss;
	struct sys_notify notify;
	struct k_poll_event sevt = K_POLL_EVENT_INITIALIZER(K_POLL_TYPE_SIGNAL,
							    K_POLL_MODE_NOTIFY_ONLY,
							    &ss);

	k_poll_signal_init(&ss);
	sys_notify_init_signal(&notify, &ss);

	uint32_t t0 = k_uptime_get_32();

	rc = maxim_ds3231_set(ds3231, &sp, &notify);

	printk("\nSet %s at %u ms past: %d\n", format_time(sp.rtc.tv_sec, sp.rtc.tv_nsec),
	       syncclock, rc);

	/* Wait for the set to complete */
	rc = k_poll(&sevt, 1, K_FOREVER);

	uint32_t t1 = k_uptime_ticks();
	printk("begins the timer");

	/* Delay so log messages from sync can complete */
	k_sleep(K_MSEC(10000));
	printk("stops the timer");
	uint32_t t2 = k_uptime_ticks();

	printk("Synchronize final: %d %d in %u ms\n", rc, ss.result, t2 - t1);

	rc = maxim_ds3231_get_syncpoint(ds3231, &sp);
	printk("wrote sync %d: %u %u at %u\n", rc,
	       (uint32_t)sp.rtc.tv_sec, (uint32_t)sp.rtc.tv_nsec,
	       sp.syncclock);
}

Our deck:

RE: ds3231 RTC changes the internal clock frequency in nrf52840

qwertynoon — Wed, 20 Apr 2022 16:48:50 GMT

Could you please explain your issue with detail.