C++ refactoring, plus low-power support, plus software-based SPI CS

I'm backlogged.

Task.h

@@ -0,0 +1,85 @@
+/*
+ * Copyright (C) 2019  Max Regan
+ *
+ * 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.
+ */
+
+#pragma once
+
+#include "ReturnCode.h"
+#include "Time.h"
+#include "SystemTime.h"
+
+namespace Common {
+namespace Schedule {
+
+enum class ScheduleType {
+  AT_TIME,
+  NEVER,
+};
+
+class NextTime {
+public:
+    NextTime() :
+        m_type(ScheduleType::NEVER),
+        m_time(0)
+        {}
+
+    static inline NextTime in(time_t offset) {
+        time_t time = 0;
+        /* If this call fails, we likely haven't initialized the timer
+         * yet, so just treat offset as the time- hopefully the system
+         * timer will be initialzed soon
+         */
+        BSP::SystemTimer::get_time(time);
+        time += offset;
+        return {ScheduleType::AT_TIME, time };
+    }
+
+    static inline NextTime never() {
+        return { ScheduleType::NEVER, 0 };
+    }
+
+    static inline NextTime asap() {
+        return { ScheduleType::AT_TIME, 0 };
+    }
+
+    static inline NextTime at(time_t time) {
+        return { ScheduleType::AT_TIME, time };
+    }
+
+    inline ScheduleType get_type() { return m_type; }
+    inline time_t get_time() { return m_time; }
+
+private:
+    NextTime(ScheduleType type, time_t time) :
+        m_type(type),
+        m_time(time)
+        {}
+
+    ScheduleType m_type;
+    time_t m_time;
+};
+
+class Task {
+public:
+  virtual NextTime execute() = 0;
+};
+
+} // namespace Schedule
+} // namespace Common