STM32: added function to retrieve the clock frequency of APB/AHB busses

meson.build

@@ -214,6 +214,7 @@ stm32f405_src = ['platform/mcu/STM32F4xx/boot/startup.cpp',
                  'platform/mcu/STM32F4xx/drivers/USART3.cpp',
                  'platform/mcu/STM32F4xx/drivers/flash.c',
                  'platform/mcu/STM32F4xx/drivers/rng.c',
+                 'platform/mcu/STM32F4xx/drivers/rcc.c',
                  'platform/mcu/STM32F4xx/drivers/i2c_stm32.c',
                  'platform/mcu/STM32F4xx/drivers/spi_stm32.c',
                  'platform/mcu/STM32F4xx/drivers/adc_stm32.c',

platform/mcu/STM32F4xx/drivers/rcc.c

@@ -0,0 +1,68 @@
+/***************************************************************************
+ *   Copyright (C) 2024 by Federico Amedeo Izzo IU2NUO,                    *
+ *                         Niccolò Izzo IU2KIN                             *
+ *                         Frederik Saraci IU2NRO                          *
+ *                         Silvano Seva IU2KWO                             *
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 3 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ *   This program is distributed in the hope that it will be useful,       *
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
+ *   GNU General Public License for more details.                          *
+ *                                                                         *
+ *   You should have received a copy of the GNU General Public License     *
+ *   along with this program; if not, see <http://www.gnu.org/licenses/>   *
+ ***************************************************************************/
+
+#include <stm32f4xx.h>
+#include <stdint.h>
+#include "rcc.h"
+
+static uint32_t busClockFreq[PERIPH_BUS_NUM] = {0};
+
+static void updateBusClockFreq(const uint8_t bus)
+{
+    uint32_t preBits;
+    uint32_t clkDiv = 1;
+
+    switch(bus)
+    {
+        case PERIPH_BUS_AHB:
+            preBits = (RCC->CFGR >> 4) & 0x0F;
+            if((preBits & 0x08) != 0)
+                clkDiv = 1 << ((preBits & 0x07) + 1);
+            break;
+
+        case PERIPH_BUS_APB1:
+            preBits = (RCC->CFGR >> 10) & 0x07;
+            if((preBits & 0x04) != 0)
+                clkDiv = 1 << ((preBits & 0x03) + 1);
+            break;
+
+        case PERIPH_BUS_APB2:
+            preBits = (RCC->CFGR >> 13) & 0x07;
+            if((preBits & 0x04) != 0)
+                clkDiv = 1 << ((preBits & 0x03) + 1);
+            break;
+
+        default:
+            break;
+    }
+
+    busClockFreq[bus] = SystemCoreClock / clkDiv;
+}
+
+uint32_t rcc_getBusClock(const uint8_t bus)
+{
+    if(bus >= PERIPH_BUS_NUM)
+        return 0;
+
+    if(busClockFreq[bus] == 0)
+        updateBusClockFreq(bus);
+
+    return busClockFreq[bus];
+}

platform/mcu/STM32F4xx/drivers/rcc.h

@@ -0,0 +1,54 @@
+/***************************************************************************
+ *   Copyright (C) 2024 by Federico Amedeo Izzo IU2NUO,                    *
+ *                         Niccolò Izzo IU2KIN                             *
+ *                         Frederik Saraci IU2NRO                          *
+ *                         Silvano Seva IU2KWO                             *
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 3 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ *   This program is distributed in the hope that it will be useful,       *
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
+ *   GNU General Public License for more details.                          *
+ *                                                                         *
+ *   You should have received a copy of the GNU General Public License     *
+ *   along with this program; if not, see <http://www.gnu.org/licenses/>   *
+ ***************************************************************************/
+
+#ifndef RCC_H
+#define RCC_H
+
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * Enumeration type for STM32 internal busses.
+ */
+enum PeriphBus
+{
+    PERIPH_BUS_AHB  = 0,
+    PERIPH_BUS_APB1 = 1,
+    PERIPH_BUS_APB2 = 2,
+
+    PERIPH_BUS_NUM
+};
+
+/**
+ * Get the clock frequency of a given peripheral bus.
+ *
+ * @param bus: bus identifier.
+ * @return bus clock frequency in Hz or zero in case of errors.
+ */
+uint32_t rcc_getBusClock(const uint8_t bus);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* RCC_H */