mimxrt/machine_rtc: Add the RTC class to the machine module.

Initial version, using the LP RTC clock.  It provides setting the date and
time with rtc.init() or rtc.datetime(), and reading the date and time with
rtc.datetime() or rtc.now().  The method weekday() reports the weekday of
the current date.  It starts with 0 for Monday.

The tuple order for datetime() and now() matches the CPython sequence:
(year, month, day, hour, minute, second, microsecond, TZ).  TZ is ignored
and reported as None.  Microsecond is provided at a best effort.

If a battery is not supplied, the default boot date/time is 1970/1/1 0:0:0.
With a battery, the clock continues to run even when the board is not
powered.  The clock is quite precise.  If not, using rtc.calibration() may
help.

ports/mimxrt/Makefile

@@ -108,6 +108,7 @@ SRC_TINYUSB_IMX_C += \
 	$(MCU_DIR)/drivers/fsl_flexram.c \
 	$(MCU_DIR)/drivers/fsl_flexspi.c \
 	$(MCU_DIR)/drivers/fsl_pit.c \
+	$(MCU_DIR)/drivers/fsl_snvs_lp.c \
 	$(MCU_DIR)/drivers/fsl_trng.c \
 
 SRC_C = \
@@ -120,6 +121,7 @@ SRC_C = \
 	$(BOARD_DIR)/flash_config.c \
 	machine_led.c \
 	machine_pin.c \
+	machine_rtc.c \
 	machine_timer.c \
 	mimxrt_flash.c \
 	modutime.c \
@@ -146,6 +148,7 @@ SRC_S = lib/utils/gchelper_m3.s \
 SRC_QSTR += \
 	machine_led.c \
 	machine_pin.c \
+	machine_rtc.c \
 	machine_timer.c \
 	mimxrt_flash.c \
 	modutime.c \

ports/mimxrt/machine_rtc.c

@@ -0,0 +1,156 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2021 Damien P. George
+ * Copyright (c) 2021 "Robert Hammelrath" <robert@hammelrath.com>
+ *
+ * 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:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * 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 "py/runtime.h"
+#include "modmachine.h"
+#include "ticks.h"
+#include "fsl_snvs_lp.h"
+
+typedef struct _machine_rtc_obj_t {
+    mp_obj_base_t base;
+    mp_obj_t callback;
+} machine_rtc_obj_t;
+
+// Singleton RTC object.
+STATIC const machine_rtc_obj_t machine_rtc_obj = {{&machine_rtc_type}};
+
+// Calculate the weekday from the date.
+// The result is zero based with 0 = Sunday.
+// by Michael Keith and Tom Craver, 1990.
+static int calc_weekday(int y, int m, int d) {
+    return (d += m < 3 ? y-- : y - 2, 23 * m / 9 + d + 4 + y / 4 - y / 100 + y / 400) % 7;
+}
+
+STATIC mp_obj_t machine_rtc_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *args) {
+    // Check arguments.
+    mp_arg_check_num(n_args, n_kw, 0, 0, false);
+
+    // Start up the RTC if needed.
+    SNVS_LP_SRTC_StartTimer(SNVS);
+
+    // Return constant object.
+    return (mp_obj_t)&machine_rtc_obj;
+}
+
+STATIC mp_obj_t machine_rtc_datetime_helper(size_t n_args, const mp_obj_t *args) {
+    if (n_args == 1) {
+        // Get date and time.
+        snvs_lp_srtc_datetime_t srtc_date;
+        SNVS_LP_SRTC_GetDatetime(SNVS, &srtc_date);
+
+        mp_obj_t tuple[8] = {
+            mp_obj_new_int(srtc_date.year),
+            mp_obj_new_int(srtc_date.month),
+            mp_obj_new_int(srtc_date.day),
+            mp_obj_new_int(srtc_date.hour),
+            mp_obj_new_int(srtc_date.minute),
+            mp_obj_new_int(srtc_date.second),
+            mp_obj_new_int(ticks_us64() % 1000000),
+            mp_const_none,
+        };
+        return mp_obj_new_tuple(8, tuple);
+    } else {
+        // Set date and time.
+        mp_obj_t *items;
+        mp_int_t year;
+        mp_obj_get_array_fixed_n(args[1], 8, &items);
+
+        snvs_lp_srtc_datetime_t srtc_date;
+        year = mp_obj_get_int(items[0]);
+        srtc_date.year = year >= 100 ? year : year + 2000; // allow 21 for 2021
+        srtc_date.month = mp_obj_get_int(items[1]);
+        srtc_date.day = mp_obj_get_int(items[2]);
+        srtc_date.hour = mp_obj_get_int(items[3]);
+        srtc_date.minute = mp_obj_get_int(items[4]);
+        srtc_date.second = mp_obj_get_int(items[5]);
+        if (SNVS_LP_SRTC_SetDatetime(SNVS, &srtc_date) != kStatus_Success) {
+            mp_raise_ValueError(NULL);
+        }
+
+        return mp_const_none;
+    }
+}
+
+STATIC mp_obj_t machine_rtc_datetime(mp_uint_t n_args, const mp_obj_t *args) {
+    return machine_rtc_datetime_helper(n_args, args);
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(machine_rtc_datetime_obj, 1, 2, machine_rtc_datetime);
+
+STATIC mp_obj_t machine_rtc_now(mp_obj_t self_in) {
+    return machine_rtc_datetime_helper(1, &self_in);
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(machine_rtc_now_obj, machine_rtc_now);
+
+STATIC mp_obj_t machine_rtc_init(mp_obj_t self_in, mp_obj_t date) {
+    mp_obj_t args[2] = {self_in, date};
+    machine_rtc_datetime_helper(2, args);
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_2(machine_rtc_init_obj, machine_rtc_init);
+
+STATIC mp_obj_t machine_rtc_weekday(mp_obj_t self_in) {
+    (void)self_in; // unused
+    int day;
+    snvs_lp_srtc_datetime_t srtc_date;
+    SNVS_LP_SRTC_GetDatetime(SNVS, &srtc_date);
+    day = calc_weekday(srtc_date.year, srtc_date.month, srtc_date.day);
+    return MP_OBJ_NEW_SMALL_INT((day + 6) % 7);
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(machine_rtc_weekday_obj, machine_rtc_weekday);
+
+// calibration(cal)
+// When the argument is a number in the range [-16 to 15], set the calibration value.
+STATIC mp_obj_t machine_rtc_calibration(mp_obj_t self_in, mp_obj_t cal_in) {
+    mp_int_t cal = 0;
+    snvs_lp_srtc_config_t snvsSrtcConfig;
+    cal = mp_obj_get_int(cal_in);
+    if (cal < -16 || cal > 15) {
+        mp_raise_ValueError(MP_ERROR_TEXT("value out of range -16 to 15"));
+    } else {
+        snvsSrtcConfig.srtcCalEnable = true;
+        snvsSrtcConfig.srtcCalValue = cal & 0x1f; // 5 bit 2's complement
+        SNVS_LP_SRTC_Init(SNVS, &snvsSrtcConfig);
+    }
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_2(machine_rtc_calibration_obj, machine_rtc_calibration);
+
+STATIC const mp_rom_map_elem_t machine_rtc_locals_dict_table[] = {
+    { MP_ROM_QSTR(MP_QSTR_init), MP_ROM_PTR(&machine_rtc_init_obj) },
+    { MP_ROM_QSTR(MP_QSTR_datetime), MP_ROM_PTR(&machine_rtc_datetime_obj) },
+    { MP_ROM_QSTR(MP_QSTR_now), MP_ROM_PTR(&machine_rtc_now_obj) },
+    { MP_ROM_QSTR(MP_QSTR_weekday), MP_ROM_PTR(&machine_rtc_weekday_obj) },
+    { MP_ROM_QSTR(MP_QSTR_calibration), MP_ROM_PTR(&machine_rtc_calibration_obj) },
+};
+STATIC MP_DEFINE_CONST_DICT(machine_rtc_locals_dict, machine_rtc_locals_dict_table);
+
+const mp_obj_type_t machine_rtc_type = {
+    { &mp_type_type },
+    .name = MP_QSTR_RTC,
+    .make_new = machine_rtc_make_new,
+    .locals_dict = (mp_obj_t)&machine_rtc_locals_dict,
+};

ports/mimxrt/modmachine.c

@@ -56,6 +56,7 @@ STATIC const mp_rom_map_elem_t machine_module_globals_table[] = {
     #endif
     { MP_ROM_QSTR(MP_QSTR_Pin),                 MP_ROM_PTR(&machine_pin_type) },
     { MP_ROM_QSTR(MP_QSTR_Timer),               MP_ROM_PTR(&machine_timer_type) },
+    { MP_ROM_QSTR(MP_QSTR_RTC),                 MP_ROM_PTR(&machine_rtc_type) },
 };
 STATIC MP_DEFINE_CONST_DICT(machine_module_globals, machine_module_globals_table);
 

ports/mimxrt/modmachine.h

@@ -30,6 +30,7 @@
 #include "py/obj.h"
 
 extern const mp_obj_type_t machine_timer_type;
+extern const mp_obj_type_t machine_rtc_type;
 
 void machine_timer_init_PIT(void);