rp2/machine_rtc: Add initial support for RTC.

Initial support for machine.RTC on rp2 port. It only supports datetime()
method and nothing else. The method gets/returns a tuple of 8 items, just
like esp32 port, for example, but the usec parameter is ignored as the RP2
RTC only works up to seconds precision.

The Pico RTC isn't very useful as the time is lost during reset and there
seems to be no way to easily power up just the RTC clock with a low current
voltage, but still there seems to be use-cases for that, see issues #6831,
and a Thonny issue #1592. It was also requested for inclusion on v1.15
roadmap on #6832.

Signed-off-by: Krzysztof Adamski <k@japko.eu>

ports/rp2/CMakeLists.txt

@@ -86,6 +86,7 @@ set(MICROPY_SOURCE_PORT
     machine_i2c.c
     machine_pin.c
     machine_pwm.c
+    machine_rtc.c
     machine_spi.c
     machine_timer.c
     machine_uart.c
@@ -113,6 +114,7 @@ set(MICROPY_SOURCE_QSTR
     ${PROJECT_SOURCE_DIR}/machine_i2c.c
     ${PROJECT_SOURCE_DIR}/machine_pin.c
     ${PROJECT_SOURCE_DIR}/machine_pwm.c
+    ${PROJECT_SOURCE_DIR}/machine_rtc.c
     ${PROJECT_SOURCE_DIR}/machine_spi.c
     ${PROJECT_SOURCE_DIR}/machine_timer.c
     ${PROJECT_SOURCE_DIR}/machine_uart.c
@@ -154,6 +156,7 @@ set(PICO_SDK_COMPONENTS
     pico_sync
     pico_time
     pico_unique_id
+    pico_util
     tinyusb_common
     tinyusb_device
 )

ports/rp2/machine_rtc.c

@@ -0,0 +1,120 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2021 "Krzysztof Adamski" <k@japko.eu>
+ *
+ * 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 <stdio.h>
+#include <string.h>
+
+#include <time.h>
+#include <sys/time.h>
+
+#include "py/nlr.h"
+#include "py/obj.h"
+#include "py/runtime.h"
+#include "py/mphal.h"
+#include "py/mperrno.h"
+#include "lib/timeutils/timeutils.h"
+#include "hardware/rtc.h"
+#include "pico/util/datetime.h"
+#include "modmachine.h"
+
+typedef struct _machine_rtc_obj_t {
+    mp_obj_base_t base;
+} machine_rtc_obj_t;
+
+// singleton RTC object
+STATIC const machine_rtc_obj_t machine_rtc_obj = {{&machine_rtc_type}};
+
+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);
+    bool r = rtc_running();
+
+    if (!r) {
+        // This shouldn't happen as rtc_init() is already called in main so
+        // it's here just in case
+        rtc_init();
+        datetime_t t = { .month = 1, .day = 1 };
+        rtc_set_datetime(&t);
+    }
+    // return constant object
+    return (mp_obj_t)&machine_rtc_obj;
+}
+
+STATIC mp_obj_t machine_rtc_datetime(mp_uint_t n_args, const mp_obj_t *args) {
+    if (n_args == 1) {
+        bool ret;
+        datetime_t t;
+
+        ret = rtc_get_datetime(&t);
+        if (!ret) {
+            mp_raise_OSError(MP_EIO);
+        }
+
+        mp_obj_t tuple[8] = {
+            mp_obj_new_int(t.year),
+            mp_obj_new_int(t.month),
+            mp_obj_new_int(t.day),
+            mp_obj_new_int(t.dotw),
+            mp_obj_new_int(t.hour),
+            mp_obj_new_int(t.min),
+            mp_obj_new_int(t.sec),
+            mp_obj_new_int(0)
+        };
+
+        return mp_obj_new_tuple(8, tuple);
+    } else {
+        mp_obj_t *items;
+
+        mp_obj_get_array_fixed_n(args[1], 8, &items);
+
+        datetime_t t = {
+            .year = mp_obj_get_int(items[0]),
+            .month = mp_obj_get_int(items[1]),
+            .day = mp_obj_get_int(items[2]),
+            .dotw = mp_obj_get_int(items[3]),
+            .hour = mp_obj_get_int(items[4]),
+            .min = mp_obj_get_int(items[5]),
+            .sec = mp_obj_get_int(items[6]),
+        };
+
+        rtc_set_datetime(&t);
+
+    }
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(machine_rtc_datetime_obj, 1, 2, machine_rtc_datetime);
+
+STATIC const mp_rom_map_elem_t machine_rtc_locals_dict_table[] = {
+    { MP_ROM_QSTR(MP_QSTR_datetime), MP_ROM_PTR(&machine_rtc_datetime_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/rp2/modmachine.c

@@ -164,6 +164,7 @@ STATIC const mp_rom_map_elem_t machine_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR_SoftI2C),             MP_ROM_PTR(&mp_machine_soft_i2c_type) },
     { MP_ROM_QSTR(MP_QSTR_Pin),                 MP_ROM_PTR(&machine_pin_type) },
     { MP_ROM_QSTR(MP_QSTR_PWM),                 MP_ROM_PTR(&machine_pwm_type) },
+    { MP_ROM_QSTR(MP_QSTR_RTC),                 MP_ROM_PTR(&machine_rtc_type) },
     { MP_ROM_QSTR(MP_QSTR_Signal),              MP_ROM_PTR(&machine_signal_type) },
     { MP_ROM_QSTR(MP_QSTR_SPI),                 MP_ROM_PTR(&machine_spi_type) },
     { MP_ROM_QSTR(MP_QSTR_SoftSPI),             MP_ROM_PTR(&mp_machine_soft_spi_type) },

ports/rp2/modmachine.h

@@ -7,6 +7,7 @@ extern const mp_obj_type_t machine_adc_type;
 extern const mp_obj_type_t machine_hw_i2c_type;
 extern const mp_obj_type_t machine_pin_type;
 extern const mp_obj_type_t machine_pwm_type;
+extern const mp_obj_type_t machine_rtc_type;
 extern const mp_obj_type_t machine_spi_type;
 extern const mp_obj_type_t machine_timer_type;
 extern const mp_obj_type_t machine_uart_type;