Merge pull request #13394 from benpicco/atmega-rtc

cpu/atmega_common: implement emulated RTC support

boards/atmega256rfr2-xpro/Makefile.features

@@ -2,6 +2,7 @@ CPU = atmega256rfr2
 
 FEATURES_PROVIDED += periph_adc
 FEATURES_PROVIDED += periph_i2c
+FEATURES_PROVIDED += periph_rtc
 FEATURES_PROVIDED += periph_rtt
 FEATURES_PROVIDED += periph_spi
 FEATURES_PROVIDED += periph_timer

boards/avr-rss2/Makefile.features

@@ -2,6 +2,7 @@ CPU = atmega256rfr2
 
 FEATURES_PROVIDED += periph_adc
 FEATURES_PROVIDED += periph_i2c
+FEATURES_PROVIDED += periph_rtc
 FEATURES_PROVIDED += periph_rtt
 FEATURES_PROVIDED += periph_spi
 FEATURES_PROVIDED += periph_timer

boards/derfmega128/Makefile.features

@@ -2,6 +2,7 @@ CPU = atmega128rfa1
 
 FEATURES_PROVIDED += periph_adc
 FEATURES_PROVIDED += periph_i2c
+FEATURES_PROVIDED += periph_rtc
 FEATURES_PROVIDED += periph_rtt
 FEATURES_PROVIDED += periph_spi
 FEATURES_PROVIDED += periph_timer

boards/derfmega256/Makefile.features

@@ -2,6 +2,7 @@ CPU = atmega256rfr2
 
 FEATURES_PROVIDED += periph_adc
 FEATURES_PROVIDED += periph_i2c
+FEATURES_PROVIDED += periph_rtc
 FEATURES_PROVIDED += periph_rtt
 FEATURES_PROVIDED += periph_spi
 FEATURES_PROVIDED += periph_timer

boards/mega-xplained/Makefile.features

@@ -3,6 +3,7 @@ CPU = atmega1284p
 # Put defined MCU peripherals here (in alphabetical order)
 FEATURES_PROVIDED += periph_adc
 FEATURES_PROVIDED += periph_i2c
+FEATURES_PROVIDED += periph_rtc
 FEATURES_PROVIDED += periph_rtt
 FEATURES_PROVIDED += periph_spi
 FEATURES_PROVIDED += periph_timer

boards/microduino-corerf/Makefile.features

@@ -3,6 +3,7 @@ CPU = atmega128rfa1
 # This board is based on an atmega CPU, thus import the features from it
 FEATURES_PROVIDED += periph_adc
 FEATURES_PROVIDED += periph_i2c
+FEATURES_PROVIDED += periph_rtc
 FEATURES_PROVIDED += periph_rtt
 FEATURES_PROVIDED += periph_spi
 FEATURES_PROVIDED += periph_timer

cpu/atmega_common/Makefile.features

@@ -6,3 +6,6 @@ FEATURES_PROVIDED += periph_gpio periph_gpio_irq
 FEATURES_PROVIDED += periph_pm
 FEATURES_PROVIDED += periph_cpuid
 FEATURES_PROVIDED += periph_wdt
+
+FEATURES_CONFLICT += periph_rtc:periph_rtt
+FEATURES_CONFLICT_MSG += "On ATmega, the RTC and RTT use to the same hardware timer."

cpu/atmega_common/periph/rtc.c

@@ -0,0 +1,137 @@
+/*
+ * Copyright (C) 2020 Benjamin Valentin
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser General
+ * Public License v2.1. See the file LICENSE in the top level directory for more
+ * details.
+ */
+
+/**
+ * @ingroup     drivers_periph_rtc
+ * @{
+ *
+ * @file
+ * @brief       Basic RTC implementation based on a 1 Hz clock
+ *
+ * @note        Unlike a real RTC, this emulated version is not guaranteed to keep
+ *              time across reboots or deep sleep.
+ *
+ * @author      Benjamin Valentin <benjamin.valentin@ml-pa.com>
+ *
+ * @}
+ */
+
+#include "periph/rtc.h"
+
+/* In .noinit so we don't reset the counter on reboot */
+static struct tm tm_now __attribute__((section(".noinit")));
+static struct tm tm_alarm __attribute__((section(".noinit")));
+
+static bool isr_flag;
+static rtc_alarm_cb_t alarm_cb;
+static void *alarm_cb_arg;
+
+/* will be called every second */
+ISR(TIMER2_OVF_vect)
+{
+    atmega_enter_isr();
+
+    isr_flag = !isr_flag;
+
+    if (++tm_now.tm_sec > 60) {
+        rtc_tm_normalize(&tm_now);
+    }
+
+    if (alarm_cb && rtc_tm_compare(&tm_now, &tm_alarm) == 0) {
+        alarm_cb(alarm_cb_arg);
+    }
+
+    atmega_exit_isr();
+}
+
+void rtc_init(void)
+{
+    static const struct tm zero = {0};
+
+    /* Disable all timer 2 interrupts */
+    TIMSK2 = 0;
+
+    /* avoid negative time values on init (uninitialized memory) */
+    if (!rtc_tm_valid(&tm_now)) {
+        tm_now = zero;
+    }
+
+    /* Select asynchronous 32 kHz clock source */
+    ASSR = (1 << AS2);
+
+    /* select normal operation */
+    TCCR2A = 0x0;
+
+    /* select divider 128 -> 1 Hz */
+    TCCR2B = 0x5;
+
+    /* Clear interrupt flags */
+    TIFR2 = (1 << OCF2B) | (1 << OCF2A) | (1 << TOV2);
+
+    /* Enable 8-bit overflow interrupt */
+    TIMSK2 |= (1 << TOIE2);
+}
+
+int rtc_set_time(struct tm *time)
+{
+    /* second starts now */
+    TCNT2 = 0;
+
+    tm_now = *time;
+
+    return 0;
+}
+
+int rtc_get_time(struct tm *time)
+{
+    bool tmp = isr_flag;
+
+    *time = tm_now;
+
+    /* check if interrupt happened while
+       reading the time struct */
+    if (isr_flag != tmp) {
+        *time = tm_now;
+    }
+
+    return 0;
+}
+
+int rtc_get_alarm(struct tm *time)
+{
+    *time = tm_alarm;
+
+    return 0;
+}
+
+int rtc_set_alarm(struct tm *time, rtc_alarm_cb_t cb, void *arg)
+{
+    rtc_tm_normalize(time);
+
+    alarm_cb = NULL;    /* disable alarm */
+    tm_alarm = *time;
+    alarm_cb_arg = arg;
+    alarm_cb = cb;      /* enable alarm */
+
+    return 0;
+}
+
+void rtc_clear_alarm(void)
+{
+    alarm_cb = NULL;
+}
+
+void rtc_poweron(void)
+{
+    power_timer2_enable();
+}
+
+void rtc_poweroff(void)
+{
+    power_timer2_disable();
+}

drivers/include/periph/rtc.h

@@ -37,6 +37,7 @@
 #ifndef PERIPH_RTC_H
 #define PERIPH_RTC_H
 
+#include <stdbool.h>
 #include <stdint.h>
 #include <time.h>
 #include "periph_conf.h"
@@ -169,6 +170,19 @@ uint32_t rtc_mktime(struct tm *t);
  */
 void rtc_localtime(uint32_t time, struct tm *t);
 
+/**
+ * @brief Verify that a time struct @p t contains valid data.
+ *
+ * @note    This function checks whether the fields of the
+ *          struct @p t are positive and within the bounds set
+ *          by @ref rtc_tm_normalize.
+ *
+ * @param[in] t       The struct to be checked.
+ *
+ * @return            true when valid, false if not
+ */
+bool rtc_tm_valid(const struct tm *t);
+
 #ifdef __cplusplus
 }
 #endif

drivers/periph_common/rtc.c

@@ -231,3 +231,34 @@ int rtc_tm_compare(const struct tm *a, const struct tm *b)
 
     return 0;
 }
+
+bool rtc_tm_valid(const struct tm *t)
+{
+    if (t->tm_sec < 0) {
+        return false;
+    }
+
+    if (t->tm_min < 0) {
+        return false;
+    }
+
+    if (t->tm_hour < 0) {
+        return false;
+    }
+
+    if (t->tm_mday < 0) {
+        return false;
+    }
+
+    if (t->tm_mon < 0) {
+        return false;
+    }
+
+    if (t->tm_year < 0) {
+        return false;
+    }
+
+    struct tm norm = *t;
+    rtc_tm_normalize(&norm);
+    return rtc_tm_compare(t, &norm) == 0;
+}