rtc.c

/* Teensyduino Core Library
 * http://www.pjrc.com/teensy/
 * Copyright (c) 2019 PJRC.COM, LLC.
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * 1. The above copyright notice and this permission notice shall be 
 * included in all copies or substantial portions of the Software.
 *
 * 2. If the Software is incorporated into a build system that allows 
 * selection among a list of target devices, then similar target
 * devices manufactured by PJRC.COM must be included in the list of
 * target devices and selectable in the same manner.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#include "imxrt.h"
#include "debug/printf.h"
#include <sys/time.h> // for struct timeval

unsigned long rtc_get(void)
{
	uint32_t hi1 = SNVS_HPRTCMR;
	uint32_t lo1 = SNVS_HPRTCLR;
	while (1) {
		uint32_t hi2 = SNVS_HPRTCMR;
		uint32_t lo2 = SNVS_HPRTCLR;
		if (lo1 == lo2 && hi1 == hi2) {
			return (hi2 << 17) | (lo2 >> 15);
		}
		hi1 = hi2;
		lo1 = lo2;
	}
}

void rtc_set(unsigned long t)
{
	// stop the RTC
	SNVS_HPCR &= ~(SNVS_HPCR_RTC_EN | SNVS_HPCR_HP_TS);
	while (SNVS_HPCR & SNVS_HPCR_RTC_EN); // wait
	// stop the SRTC
	SNVS_LPCR &= ~SNVS_LPCR_SRTC_ENV;
	while (SNVS_LPCR & SNVS_LPCR_SRTC_ENV); // wait
	// set the SRTC
	SNVS_LPSRTCLR = t << 15;
	SNVS_LPSRTCMR = t >> 17;
	// start the SRTC
	SNVS_LPCR |= SNVS_LPCR_SRTC_ENV;
	while (!(SNVS_LPCR & SNVS_LPCR_SRTC_ENV)); // wait
	// start the RTC and sync it to the SRTC
	SNVS_HPCR |= SNVS_HPCR_RTC_EN | SNVS_HPCR_HP_TS;
}

void rtc_compensate(int adjust __attribute__((unused)))
{
}

// https://github.com/arduino-libraries/ArduinoBearSSL/issues/54
// https://forum.pjrc.com/threads/70966
__attribute__((weak))
int _gettimeofday(struct timeval *tv, void *ignore __attribute__((unused)))
{
	uint32_t hi1 = SNVS_HPRTCMR;
	uint32_t lo1 = SNVS_HPRTCLR;
	while (1) {
		uint32_t hi2 = SNVS_HPRTCMR;  // ref manual 20.3.3.1.3 page 1231
		uint32_t lo2 = SNVS_HPRTCLR;
		if (lo1 == lo2 && hi1 == hi2) {
			tv->tv_sec = (hi2 << 17) | (lo2 >> 15);
			tv->tv_usec = ((lo2 & 0x7FFF) * 15625) >> 9;
			return 0;
		}
		hi1 = hi2;
		lo1 = lo2;
	}
}