From 3d00bdf3c069031138889d7cbe975bc1a0899439 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?King=20K=C3=A9vin?= <kingkevin@cuvoodoo.info>
Date: Mon, 30 Nov 2020 14:36:33 +0100
Subject: [PATCH] application: add periodis RTC wakeup

---
 application.c | 50 +++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 41 insertions(+), 9 deletions(-)

diff --git a/application.c b/application.c
index 2d457bc..20222e3 100644
--- a/application.c
+++ b/application.c
@@ -36,10 +36,14 @@
 /** watchdog period in ms */
 #define WATCHDOG_PERIOD 10000
 
+/** wakeup frequency (i.e. least number of times per second to  perform the main loop) */
+#define WAKEUP_FREQ 16
+
 /** @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 */
+static volatile bool wakeup_flag = false; /**< flag set when wakeup timer triggered */
+static volatile bool second_flag = false; /**< flag set when a second passed */
 /** @} */
 
 size_t putc(char c)
@@ -408,6 +412,22 @@ void main(void)
 	}
 	puts("OK\n");
 
+	// setup wakeup timer for periodic checks
+	puts("setup wakeup: ");
+	// RTC needs to be configured beforehand
+	pwr_disable_backup_domain_write_protect(); // disable backup protection so we can write to the RTC registers
+	rtc_unlock(); // enable writing RTC registers
+	rtc_clear_wakeup_flag(); // clear flag for fresh start
+#if defined(MINIF401)
+	rtc_set_wakeup_time((32768 / 2) / WAKEUP_FREQ - 1, RTC_CR_WUCLKSEL_RTC_DIV2); // set wakeup time based on LSE (keep highest precision, also enables the wakeup timer)
+#else
+	rtc_set_wakeup_time((32000 / 2) / WAKEUP_FREQ - 1, RTC_CR_WUCLKSEL_RTC_DIV2); // set wakeup time based on LSI (keep highest precision, also enables the wakeup timer)
+#endif
+	rtc_enable_wakeup_timer_interrupt(); // enable interrupt
+	rtc_lock(); // disable writing RTC registers
+	// important: do not re-enable backup_domain_write_protect, since this will prevent clearing flags (but RTC registers do not need to be unlocked)
+	puts("OK\n");
+
 	// setup terminal
 	terminal_prefix = ""; // set default prefix
 	terminal_process = &process_command; // set central function to process commands
@@ -432,15 +452,13 @@ void main(void)
 			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 second has passed
-				led_toggle(); // toggle LED (good to indicate if main function is stuck)
-			}
+		if (wakeup_flag) { // time to do periodic checks
+			wakeup_flag = false; // clear flag
+		}
+		if (second_flag) { // one second passed
+			second_flag = false; // clear flag
+			led_toggle(); // toggle LED 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 {
@@ -448,3 +466,17 @@ void main(void)
 		}
 	} // main loop
 }
+
+/** interrupt service routine when the wakeup timer triggered */
+void rtc_wkup_isr(void)
+{
+	static uint16_t tick = WAKEUP_FREQ; // how many wakeup have occurred
+	exti_reset_request(EXTI22); // clear EXTI flag used by wakeup
+	rtc_clear_wakeup_flag(); // clear flag
+	wakeup_flag = true; // notify main loop
+	tick--; // count the number of ticks down (do it in the ISR to no miss any tick)
+	if (0 == tick) { // count down completed
+		second_flag = true; // notify main loop a second has passed
+		tick = WAKEUP_FREQ; // restart count down
+	}
+}