Add missing SystemInit.cpp

firmware/Bsp/Mcu/SystemInit.cpp

@@ -0,0 +1,94 @@
+/*
+ * Copyright (C) 2020  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 "Bsp/macros.h"
+#include "Mcu.h"
+
+
+void SystemInit()
+{
+    /**
+     * Use the MSI for the system clock, and disable all other clocks.
+     */
+
+#if defined(STM32L0XX)
+    // STM32L0
+    SET_TO(RCC->ICSCR,
+           RCC_ICSCR_MSIRANGE,
+           RCC_ICSCR_MSIRANGE_6);
+#elif defined(STM32L4XX)
+    // STM32L4
+    SET_TO(RCC->CR,
+           RCC_CR_MSIRANGE,
+           RCC_CR_MSIRANGE_6);
+#else
+#error "Unsupported device type"
+#endif
+
+    /*!< Set MSION bit. Set by hardware to force the MSI oscillator ON
+     * when exiting from Stop or Standby mode, or in case of a failure
+     * of the HSE oscillator used directly or indirectly as system
+     * clock. This bit cannot be cleared if the MSI is used as system
+     * clock. */
+    SET(RCC->CR,
+        RCC_CR_MSION);
+
+    /*!< Set internal representation of clock frequency to 4MHz */
+    // system_clk_freq = 4u << 22;
+
+    /*!< Reset
+     * SW[1:0] (use MSI oscillator as system clock),
+     * HPRE[3:0] (do not divide AHB clock in prescaler) ,
+     * PPRE1[2:0] (do not divide APB low-speed clock)
+     * PPRE2[2:0] (do not divide APB high-speed clock),
+     * MCOSEL[2:0] (disable MCO clock),
+     * MCOPRE[2:0] (disable MCO prescaler) */
+    CLR(RCC->CFGR,
+          RCC_CFGR_SW | ~RCC_CFGR_HPRE | RCC_CFGR_PPRE1 | RCC_CFGR_PPRE2 |
+          RCC_CFGR_MCOSEL | RCC_CFGR_MCOPRE);
+
+    /*!< Reset HSEBYP bit (disable HSE bypass) */
+    CLR(RCC->CR,
+          RCC_CR_HSEBYP);
+
+    /*!< Reset
+     * HSION (disable HSI),
+     * HSIDIVEN (disable 18MHz HSI division)
+     * HSEON (disable HSE clock)
+     * CSSHSEON (disable HSE clock monitoring)
+     * PLLON (disable PLL)
+     */
+#ifdef STM32L0XX
+    CLR(RCC->CR,
+          RCC_CR_HSION | RCC_CR_HSIDIVEN | RCC_CR_HSEON |
+          RCC_CR_CSSHSEON | RCC_CR_PLLON);
+#else
+    CLR(RCC->CR,
+          RCC_CR_HSION | RCC_CR_HSEON |
+          RCC_CR_PLLON);
+#endif
+
+    /*!< Disable all interrupts */
+    RCC->CIER = 0x00000000;
+
+    /* Vector Table Relocation in Internal FLASH */
+    SCB->VTOR = FLASH_BASE;
+}