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

I'm backlogged.

LowPower.cpp

@@ -0,0 +1,70 @@
+/*
+ * 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.
+ */
+
+#include "SystemTime.h"
+#include "LowPower.h"
+#include "macros.h"
+
+#include "stm32l0xx.h"
+
+namespace BSP {
+
+using Common::ReturnCode;
+
+ReturnCode LowPower::init()
+{
+    /* Enable Clocks */
+    SET(RCC->APB1ENR, RCC_APB1ENR_PWREN);
+
+    // FIXME: Make these configurable, will mess with power consumption
+    SET(DBGMCU->CR, DBGMCU_CR_DBG_STOP);
+    SET(DBGMCU->CR, DBGMCU_CR_DBG_SLEEP);
+    SET(DBGMCU->CR, DBGMCU_CR_DBG_STANDBY);
+    return ReturnCode::OK;
+}
+
+ReturnCode LowPower::sleep()
+{
+    return ReturnCode::FAIL;
+}
+
+ReturnCode LowPower::stop()
+{
+
+    /* Prepare to enter stop mode */
+    SET(PWR->CR, PWR_CR_CWUF); // clear WUF
+    while(PWR->CSR & PWR_CSR_WUF) {};
+    CLR(PWR->CR, PWR_CR_PDDS); // Enter stop mode when the CPU enters deepsleep
+    CLR(RCC->CFGR, RCC_CFGR_STOPWUCK); // MSI oscillator is wake-up from stop clock
+    SET(SCB->SCR, SCB_SCR_SLEEPDEEP_Msk); // low-power mode = stop mode
+    // Common::time_t time0 = ~0;
+    // SystemTimer::get_time(time0);
+    __WFI(); // enter low-power mode
+    // Common::time_t time1 = ~0;
+    // SystemTimer::get_time(time1);
+    // Common::time_t timediff = time1 - time0;
+    // volatile Common::time_t timediff2 = timediff;
+
+    return ReturnCode::OK;
+}
+
+}
+