stm32f1/application.c

/* This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */
/** STM32F1 application example
 *  @file
 *  @author King Kévin <kingkevin@cuvoodoo.info>
 *  @date 2016-2020
 */

/* standard libraries */
#include <stdint.h> // standard integer types
#include <stdlib.h> // standard utilities
#include <string.h> // string utilities
#include <time.h> // date/time utilities
#include <ctype.h> // utilities to check chars

/* STM32 (including CM3) libraries */
#include <libopencmsis/core_cm3.h> // Cortex M3 utilities
#include <libopencm3/cm3/scb.h> // vector table definition
#include <libopencm3/cm3/nvic.h> // interrupt utilities
#include <libopencm3/stm32/gpio.h> // general purpose input output library
#include <libopencm3/stm32/rcc.h> // real-time control clock library
#include <libopencm3/stm32/exti.h> // external interrupt utilities
#include <libopencm3/stm32/rtc.h> // real time clock utilities
#include <libopencm3/stm32/iwdg.h> // independent watchdog utilities
#include <libopencm3/stm32/dbgmcu.h> // debug utilities
#include <libopencm3/stm32/desig.h> // design utilities
#include <libopencm3/stm32/flash.h> // flash utilities

/* own libraries */
#include "global.h" // board definitions
#include "print.h" // printing utilities
#if !defined(STLINKV2)
#include "uart.h" // USART utilities
#endif
#include "usb_cdcacm.h" // USB CDC ACM utilities
#include "terminal.h" // handle the terminal interface
#include "menu.h" // menu utilities

/** watchdog period in ms */
#define WATCHDOG_PERIOD 10000

/** set to 0 if the RTC is reset when the board is powered on, only indicates the uptime
 *  set to 1 if VBAT can keep the RTC running when the board is unpowered, indicating the date and time
 */
#if defined(CORE_BOARD)
#define RTC_DATE_TIME 1
#else
#define RTC_DATE_TIME 0
#endif

/** number of RTC ticks per second
 *  @note use integer divider of oscillator to keep second precision
 */
#define RTC_TICKS_SECOND 4

/** RTC time when device is started */
static time_t time_start = 0;

/** @defgroup main_flags flag set in interrupts to be processed in main task
 *  @{
 */
static volatile bool rtc_internal_tick_flag = false; /**< flag set when internal RTC ticked */
/** @} */

size_t putc(char c)
{
	size_t length = 0; // number of characters printed
	static char last_c = 0; // to remember on which character we last sent
	if ('\n' == c) { // send carriage return (CR) + line feed (LF) newline for each LF
		if ('\r' != last_c) { // CR has not already been sent
#if !defined(STLINKV2)
			uart_putchar_nonblocking('\r'); // send CR over USART
#endif
			usb_cdcacm_putchar('\r'); // send CR over USB
			length++; // remember we printed 1 character
		}
	}
#if !defined(STLINKV2)
	uart_putchar_nonblocking(c); // send byte over USART
#endif
	usb_cdcacm_putchar(c); // send byte over USB
	length++; // remember we printed 1 character
	last_c = c; // remember last character
	return length; // return number of characters printed
}

/** display available commands
 *  @param[in] argument no argument required
 */
static void command_help(void* argument);

/** show software and hardware version
 *  @param[in] argument no argument required
 */
static void command_version(void* argument);

/** show uptime
 *  @param[in] argument no argument required
 */
static void command_uptime(void* argument);

#if RTC_DATE_TIME
/** show date and time
 *  @param[in] argument date and time to set
 */
static void command_datetime(void* argument);
#endif

/** reset board
 *  @param[in] argument no argument required
 */
static void command_reset(void* argument);

/** switch to DFU bootloader
 *  @param[in] argument no argument required
 */
static void command_bootloader(void* argument);

/** list of all supported commands */
static const struct menu_command_t menu_commands[] = {
	{
		.shortcut = 'h',
		.name = "help",
		.command_description = "display help",
		.argument = MENU_ARGUMENT_NONE,
		.argument_description = NULL,
		.command_handler = &command_help,
	},
	{
		.shortcut = 'v',
		.name = "version",
		.command_description = "show software and hardware version",
		.argument = MENU_ARGUMENT_NONE,
		.argument_description = NULL,
		.command_handler = &command_version,
	},
	{
		.shortcut = 'u',
		.name = "uptime",
		.command_description = "show uptime",
		.argument = MENU_ARGUMENT_NONE,
		.argument_description = NULL,
		.command_handler = &command_uptime,
	},
#if RTC_DATE_TIME
	{
		.shortcut = 'd',
		.name = "date",
		.command_description = "show/set date and time",
		.argument = MENU_ARGUMENT_STRING,
		.argument_description = "[YYYY-MM-DD HH:MM:SS]",
		.command_handler = &command_datetime,
	},
#endif
	{
		.shortcut = 'r',
		.name = "reset",
		.command_description = "reset board",
		.argument = MENU_ARGUMENT_NONE,
		.argument_description = NULL,
		.command_handler = &command_reset,
	},
	{
		.shortcut = 'b',
		.name = "bootloader",
		.command_description = "reboot into DFU bootloader",
		.argument = MENU_ARGUMENT_NONE,
		.argument_description = NULL,
		.command_handler = &command_bootloader,
	},
};

static void command_help(void* argument)
{
	(void)argument; // we won't use the argument
	printf("available commands:\n");
	menu_print_commands(menu_commands, LENGTH(menu_commands)); // print global commands
}

static void command_version(void* argument)
{
	(void)argument; // we won't use the argument
	printf("firmware date: %04u-%02u-%02u\n", BUILD_YEAR, BUILD_MONTH, BUILD_DAY); // show firmware build date
	// show flash size
	puts("flash size: ");
	if (0xffff == DESIG_FLASH_SIZE) {
		puts("unknown (probably a defective micro-controller\n");
	} else {
		printf("%u KB\n", DESIG_FLASH_SIZE);
	}
	const uint16_t dev_id = DBGMCU_IDCODE & DBGMCU_IDCODE_DEV_ID_MASK;
	const uint16_t rev_id = DBGMCU_IDCODE >> 16;
	printf("MCUID: DEV_ID=0x%03x REV_ID=0x%04x\n", dev_id, rev_id);
	// display device identity
	printf("device id: %08x%08x%04x%04x\n", DESIG_UNIQUE_ID2, DESIG_UNIQUE_ID1, DESIG_UNIQUE_ID0 & 0xffff, DESIG_UNIQUE_ID0 >> 16);
#if DEBUG
	bool fake = false; // if details indicate it's not an STM32
	puts("chip family: ");
	switch (dev_id) {
		case 0: // DBGMCU_IDCODE is only accessible in debug mode (this is a known issue documented in STM32F10xxC/D/E Errata sheet, without workaround)
			puts("not readable, retry with debug attached");
			break;
		// from RM0008 STM32F101xx, STM32F102xx, STM32F103xx, STM32F105xx and STM32F107xx
		case 0x412:
			puts("STM32F10x low-density");
			break;
		case 0x410:
			puts("STM32F10x medium-density");
			break;
		case 0x414:
			puts("STM32F10x high-density");
			break;
		case 0x430:
			puts("STM32F10x XL-density");
			break;
		case 0x418:
			puts("STM32F10xconnectivity");
			break;
		// from RM0091 STM32F0x8
		case 0x444:
			puts("STM32F03x");
			break;
		case 0x445:
			puts("STM32F04x");
			break;
		case 0x440:
			puts("STM32F05x");
			break;
		case 0x448:
			puts("STM32F07x");
			break;
		case 0x442:
			puts("STM32F09x");
			break;
		// from RM0444 STM32G0x1
		case 0x460:
			puts("STM32G071xx/STM32G081xx");
			break;
		case 0x466:
			puts("STM32G031xx/STM32G041xx");
			break;
		// from RM0090 STM32F4x5/STM32F4x7
		case 0x413:
			puts("STM32F405/STM32F407/STM32F415/STM32F417");
			break;
		case 0x419:
			puts("STM32F42x/STM32F43x");
			break;
		// from RM0368
		case 0x423:
			puts("STM32F401xB/C");
			break;
		case 0x433:
			puts("STM32F401xD/E");
			break;
		// from RM0383
		case 0x431:
			puts("STM32F411xC/E");
			break;
		default:
			puts("unknown");
			fake = true;
			break;
	}
	putc('\n');
	puts("chip revision: ");
	switch (DBGMCU_IDCODE & DBGMCU_IDCODE_DEV_ID_MASK) {
		case 0x412:
			if (0x1000 == rev_id) {
				putc('A');
			} else {
				puts("unknown");
			}
			break;
		case 0x410:
			if (0x0000 == rev_id) {
				putc('A');
			} else if (0x2000 == rev_id) {
				putc('B');
			} else if (0x2001 == rev_id) {
				putc('Z');
			} else if (0x2003 == rev_id) {
				puts("1/2/3/X/Y");
			} else {
				puts("unknown");
			}
			break;
		case 0x414:
			if (0x1000 == rev_id) {
				puts("A/1");
			} else if (0x1001 == rev_id) {
				putc('Z');
			} else if (0x1003 == rev_id) {
				puts("1/2/3/X/Y");
			} else {
				puts("unknown");
			}
			break;
		case 0x430:
			if (0x1003 == rev_id) {
				puts("A/1");
			} else {
				puts("unknown");
			}
			break;
		case 0x418:
			if (0x1000 == rev_id) {
				putc('A');
			} else if (0x1001 == rev_id) {
				putc('Z');
			} else {
				puts("unknown");
			}
			break;
		default:
			printf("unknown");
			break;
	}
	putc('\n');
	// from RM0091 STM32F0x8 reference manual (not sure if it applies to F1)
	puts("manufacturing information:\n");
	printf("- X,Y wafer coordinate: %08x\n", DESIG_UNIQUE_ID0);
	printf("- lot number: %c%c%c%c%c%c%c\n", DESIG_UNIQUE_ID2 >> 24, DESIG_UNIQUE_ID2 >> 16, DESIG_UNIQUE_ID2 >> 8, DESIG_UNIQUE_ID2 >> 0, DESIG_UNIQUE_ID1 >> 24, DESIG_UNIQUE_ID1 >> 16, DESIG_UNIQUE_ID1 >> 8);
	printf("- wafer number: %u\n", DESIG_UNIQUE_ID1 & 0xff);
	// from ARMv7-M and Cortex-M3 TRM
	// ARMv7-M B3.2.3
	printf("CPUID: 0x%08x\n", SCB_CPUID);
	const uint8_t cpuid_implementer = (SCB_CPUID & SCB_CPUID_IMPLEMENTER) >> SCB_CPUID_IMPLEMENTER_LSB;
	printf("- implementer: %s (0x%02x)\n", 0x41 == cpuid_implementer ? "ARM" : "unknown", cpuid_implementer);
	const uint8_t cpuid_architecture = (SCB_CPUID & SCB_CPUID_CONSTANT) >> SCB_CPUID_CONSTANT_LSB;
	puts("- architecture: ");
	switch (cpuid_architecture) {
	case 0xc:
		puts("ARMv6-M");
		break;
	case 0xf:
		puts("ARMv7-M");
		break;
	default:
		fake = true;
		puts("unknown");
	}
	printf(" (0x%x)\n", cpuid_architecture);
	const uint16_t cpuid_partno = (SCB_CPUID & SCB_CPUID_PARTNO) >> SCB_CPUID_PARTNO_LSB;
	puts("- part number: ");
	switch (cpuid_partno) {
	case 0xC60:
		puts("Cortex-M0+");
		break;
	case 0xC20:
		puts("Cortex‑M0");
		break;
	case 0xC23: // the ARM spec actually mentions 0xC24
		puts("Cortex‑M3");
		break;
	case 0xC24:
		puts("Cortex‑M4");
		break;
	case 0xC27:
		puts("Cortex‑M7");
		break;
	default:
		fake = true;
		puts("unknown");
	}
	printf(" (0x%03x)\n", cpuid_partno);
	const uint8_t cpuid_variant = (SCB_CPUID & SCB_CPUID_VARIANT) >> SCB_CPUID_VARIANT_LSB;
	printf("- variant: %u\n", cpuid_variant);
	const uint8_t cpuid_revision = (SCB_CPUID & SCB_CPUID_REVISION) >> SCB_CPUID_REVISION_LSB;
	printf("- revision: %u\n", cpuid_revision);
	// ARM CoreSight B2.2.2
	const uint8_t jep106_continuation = *(uint32_t*)0xE00FFFD0 & 0x0f; // DES_2, PIDR4 bits[3:0]
	const uint8_t jep106_identification = ((*(uint32_t*)0xE00FFFE8 & 0x7) << 4) + ((*(uint32_t*)0xE00FFFE4 >> 4) & 0xf); // DES_0, PIDR1 bits[7:4] JEP106 identification code bits[3:0], DES_1, PIDR2 bits[2:0] JEP106 identification code bits[6:4]
	const uint16_t pidr_partno = ((*(uint32_t*)0xE00FFFE4 & 0xf) << 8) + (*(uint32_t*)0xE00FFFE0 & 0xff); // PART_0, PIDR0 bits[7:0] Part number bits[7:0], PART_1, PIDR1 bits[3:0] Part number bits[11:8]
	puts("JEP106 ID: ");
	if (0 == jep106_continuation && 0x20 == jep106_identification) {
		puts("STM");
	} else if (7 == jep106_continuation && 0x51 == jep106_identification) {
		puts("GigaDevice");
	} else if (4 == jep106_continuation && 0x3b == jep106_identification) {
		puts("ARM");
	} else {
		puts("unknown");
	}
	printf(" (cont.=%u, ID=0x%02x), part=0x%03x\n", jep106_continuation, jep106_identification, pidr_partno);
	// guess the micro-controller
	puts("MCU: ");
	if (1 == cpuid_variant && 1 == cpuid_revision && 0 == jep106_continuation && 0x20 == jep106_identification) { // STM32 uses Cortex-M3 r1p1 and the right JEP106 ID
		puts("STM32");
	} else if (2 == cpuid_variant && 1 == cpuid_revision && 7 == jep106_continuation && 0x51 == jep106_identification) { // GD32  uses Cortex-M3 r2p1 and the right JEP106 ID
		puts("GD32");
		fake = true;
	} else if (2 == cpuid_variant && 1 == cpuid_revision && 4 == jep106_continuation && 0x3b == jep106_identification) { // GD32  uses Cortex-M3 r2p1 and ARM JEP106 ID
		puts("CS32");
		fake = true;
	} else {
		puts("unknown");
		fake = true;
	}
	putc('\n');
	// detect fake STM32
	if (0x412 == dev_id || 0x410 == dev_id || 0x414 == dev_id || 0x430 == dev_id || 0x418 == dev_id) { // STM32F10x
		// the original STM32F10x uses a Cortex-M3 r1p1
		if (0xC23 != cpuid_partno) { // Cortex-M3
			fake = true;
		}
		if (1 != cpuid_variant) { // r1
			fake = true;
		}
		if (1 != cpuid_revision) { // p1
			fake = true;
		}
	}
	printf("this %s to be a genuine STM32\n", fake ? "does not seem" : "seems");
#endif
}

static void command_uptime(void* argument)
{
	(void)argument; // we won't use the argument
	const uint32_t uptime = (rtc_get_counter_val() - time_start) / RTC_TICKS_SECOND; // get time from internal RTC
	printf("uptime: %u.%02u:%02u:%02u\n", uptime / (24 * 60 * 60), (uptime / (60 * 60)) % 24, (uptime / 60) % 60, uptime % 60);
}

#if RTC_DATE_TIME
static void command_datetime(void* argument)
{
	char* datetime = (char*)argument; // argument is optional date time
	if (NULL == argument) { // no date and time provided, just show the current day and time
		time_t time_rtc = rtc_get_counter_val() / RTC_TICKS_SECOND; // get time from internal RTC
		struct tm* time_tm = localtime(&time_rtc); // convert time
		printf("date: %d-%02d-%02d %02d:%02d:%02d\n", 1900 + time_tm->tm_year, time_tm->tm_mon, time_tm->tm_mday, time_tm->tm_hour, time_tm->tm_min, time_tm->tm_sec);
	} else { // date and time provided, set it
		const char* malformed = "date and time malformed, expecting YYYY-MM-DD HH:MM:SS\n";
		struct tm time_tm; // to store the parsed date time
		if (strlen(datetime) != (4 + 1 + 2 + 1 + 2) + 1 + (2 + 1 + 2 + 1 + 2)) { // verify date/time is long enough
			printf(malformed);
			return;
		}
		if (!(isdigit((int8_t)datetime[0]) && isdigit((int8_t)datetime[1]) && isdigit((int8_t)datetime[2]) && isdigit((int8_t)datetime[3]) && '-' == datetime[4] && isdigit((int8_t)datetime[5]) && isdigit((int8_t)datetime[6]) && '-' == datetime[7] && isdigit((int8_t)datetime[8]) && isdigit((int8_t)datetime[9]) && ' ' == datetime[10] && isdigit((int8_t)datetime[11]) && isdigit((int8_t)datetime[12]) && ':' == datetime[13] && isdigit((int8_t)datetime[14]) && isdigit((int8_t)datetime[15]) && ':' == datetime[16] && isdigit((int8_t)datetime[17]) && isdigit((int8_t)datetime[18]))) { // verify format (good enough to not fail parsing)
			printf(malformed);
			return;
		}
		time_tm.tm_year = strtol(&datetime[0], NULL, 10) - 1900; // parse year
		time_tm.tm_mon = strtol(&datetime[5], NULL, 10); // parse month
		time_tm.tm_mday = strtol(&datetime[8], NULL, 10); // parse day
		time_tm.tm_hour = strtol(&datetime[11], NULL, 10); // parse hour
		time_tm.tm_min = strtol(&datetime[14], NULL, 10); // parse minutes
		time_tm.tm_sec = strtol(&datetime[17], NULL, 10); // parse seconds
		time_t time_rtc = mktime(&time_tm); // get back seconds
		time_start = time_rtc * RTC_TICKS_SECOND + (rtc_get_counter_val() - time_start); // update uptime with current date
		rtc_set_counter_val(time_rtc * RTC_TICKS_SECOND); // save date/time to internal RTC
		printf("date and time saved: %d-%02d-%02d %02d:%02d:%02d\n", 1900 + time_tm.tm_year, time_tm.tm_mon, time_tm.tm_mday, time_tm.tm_hour, time_tm.tm_min, time_tm.tm_sec);
	}
}
#endif

static void command_reset(void* argument)
{
	(void)argument; // we won't use the argument
	scb_reset_system(); // reset device
	while (true); // wait for the reset to happen
}

static void command_bootloader(void* argument)
{
	(void)argument; // we won't use the argument
	// set DFU magic to specific RAM location
	__dfu_magic[0] = 'D';
	__dfu_magic[1] = 'F';
	__dfu_magic[2] = 'U';
	__dfu_magic[3] = '!';
	scb_reset_system(); // reset system (core and peripherals)
	while (true); // wait for the reset to happen
}

/** process user command
 *  @param[in] str user command string (\0 ended)
 */
static void process_command(char* str)
{
	// ensure actions are available
	if (NULL == menu_commands || 0 == LENGTH(menu_commands)) {
		return;
	}
	// don't handle empty lines
	if (!str || 0 == strlen(str)) {
		return;
	}
	bool command_handled = false;
	if (!command_handled) {
		command_handled = menu_handle_command(str, menu_commands, LENGTH(menu_commands)); // try if this is not a global command
	}
	if (!command_handled) {
		printf("command not recognized. enter help to list commands\n");
	}
}

/** program entry point
 *  this is the firmware function started by the micro-controller
 */
void main(void);
void main(void)
{
	rcc_clock_setup_in_hse_8mhz_out_72mhz(); // use 8 MHz high speed external clock to generate 72 MHz internal clock

#if DEBUG
	// enable functionalities for easier debug
	DBGMCU_CR |= DBGMCU_CR_IWDG_STOP; // stop independent watchdog counter when code is halted
	DBGMCU_CR |= DBGMCU_CR_WWDG_STOP; // stop window watchdog counter when code is halted
	DBGMCU_CR |= DBGMCU_CR_STANDBY; // allow debug also in standby mode (keep digital part and clock powered)
	DBGMCU_CR |= DBGMCU_CR_STOP; // allow debug also in stop mode (keep clock powered)
	DBGMCU_CR |= DBGMCU_CR_SLEEP; // allow debug also in sleep mode (keep clock powered)
#else
	// setup watchdog to reset in case we get stuck (i.e. when an error occurred)
	iwdg_set_period_ms(WATCHDOG_PERIOD); // set independent watchdog period
	iwdg_start(); // start independent watchdog
#endif

	board_setup(); // setup board
#if !defined(STLINKV2)
	uart_setup(); // setup USART (for printing)
#endif
	usb_cdcacm_setup(); // setup USB CDC ACM (for printing)
	puts("\nwelcome to the CuVoodoo STM32F1 example application\n"); // print welcome message

#if DEBUG
	// show reset cause
	if (RCC_CSR & (RCC_CSR_LPWRRSTF | RCC_CSR_WWDGRSTF | RCC_CSR_IWDGRSTF | RCC_CSR_SFTRSTF | RCC_CSR_PORRSTF | RCC_CSR_PINRSTF)) {
		puts("reset cause(s):");
		if (RCC_CSR & RCC_CSR_LPWRRSTF) {
			puts(" low-power");
		}
		if (RCC_CSR & RCC_CSR_WWDGRSTF) {
			puts(" window-watchdog");
		}
		if (RCC_CSR & RCC_CSR_IWDGRSTF) {
			puts(" independent-watchdog");
		}
		if (RCC_CSR & RCC_CSR_SFTRSTF) {
			puts(" software");
		}
		if (RCC_CSR & RCC_CSR_PORRSTF) {
			puts(" POR/PDR");
		}
		if (RCC_CSR & RCC_CSR_PINRSTF) {
			puts(" pin");
		}
		putc('\n');
		RCC_CSR |= RCC_CSR_RMVF; // clear reset flags
	}
#endif
#if !(DEBUG)
	// show watchdog information
	printf("setup watchdog: %.2fs", WATCHDOG_PERIOD / 1000.0);
	if (FLASH_OBR & FLASH_OBR_OPTERR) {
		puts(" (option bytes not set in flash: software wachtdog used, not automatically started at reset)\n");
	} else if (FLASH_OBR & FLASH_OBR_WDG_SW) {
		puts(" (software watchdog used, not automatically started at reset)\n");
	} else {
		puts(" (hardware watchdog used, automatically started at reset)\n");
	}
#endif

	// setup RTC
	puts("setup internal RTC: ");
#if defined(BLUE_PILL) || defined(STLINKV2) || defined(BLASTER) // for boards without a Low Speed External oscillator
	// note: the blue pill LSE oscillator is affected when toggling the onboard LED, thus prefer the HSE
	rtc_auto_awake(RCC_HSE, 8000000 / 128 / RTC_TICKS_SECOND - 1); // use High Speed External oscillator (8 MHz / 128) as RTC clock (VBAT can't be used to keep the RTC running)
#else // for boards with an precise Low Speed External oscillator
	rtc_auto_awake(RCC_LSE, 32768 / RTC_TICKS_SECOND - 1); // ensure internal RTC is on, uses the 32.678 kHz LSE, and the prescale is set to our tick speed, else update backup registers accordingly (power off the micro-controller for the change to take effect)
#endif
	rtc_interrupt_enable(RTC_SEC); // enable RTC interrupt on "seconds"
	nvic_enable_irq(NVIC_RTC_IRQ); // allow the RTC to interrupt
	time_start = rtc_get_counter_val(); // get start time from internal RTC
	puts("OK\n");

	// setup terminal
	terminal_prefix = ""; // set default prefix
	terminal_process = &process_command; // set central function to process commands
	terminal_setup(); // start terminal

	// start main loop
	bool action = false; // if an action has been performed don't go to sleep
	button_flag = false; // reset button flag
	while (true) { // infinite loop
		iwdg_reset(); // kick the dog
		if (user_input_available) { // user input is available
			action = true; // action has been performed
			led_toggle(); // toggle LED
			char c = user_input_get(); // store receive character
			terminal_send(c); // send received character to terminal
		}
		if (button_flag) { // user pressed button
			action = true; // action has been performed
			puts("button pressed\n");
			led_toggle(); // toggle LED
			sleep_ms(100); // wait a bit to remove noise and double trigger
			button_flag = false; // reset flag
		}
		if (rtc_internal_tick_flag) { // the internal RTC ticked
			rtc_internal_tick_flag = false; // reset flag
			action = true; // action has been performed
			if (0 == (rtc_get_counter_val() % RTC_TICKS_SECOND)) { // one seond has passed
				led_toggle(); // toggle LED (good to indicate if main function is stuck)
			}
		}
		if (action) { // go to sleep if nothing had to be done, else recheck for activity
			action = false;
		} else {
			__WFI(); // go to sleep
		}
	} // main loop
}

/** @brief interrupt service routine called when tick passed on RTC */
void rtc_isr(void)
{
	rtc_clear_flag(RTC_SEC); // clear flag
	rtc_internal_tick_flag = true; // notify to show new time
}