Boot, UART working

7 files changed, 367 insertions, 115 deletions

diff --git a/Makefile b/Makefile
index e1d6d0a..ab1ca8d 100644
--- a/Makefile
+++ b/Makefile
@@ -3,6 +3,10 @@ CUBE_PATH 		?= $(wildcard ~)/resource/STM32CubeF4
 CMSIS_PATH 		?= $(CUBE_PATH)/Drivers/CMSIS
 CMSIS_DEV_PATH  ?= $(CMSIS_PATH)/Device/ST/STM32F4xx
 HAL_PATH   		?= $(CUBE_PATH)/Drivers/STM32F4xx_HAL_Driver
+USB_PATH		?= $(CUBE_PATH)/Middlewares/ST/STM32_USB_Host_Library
+OUT 			?= out
+
+VPATH 			= .:$(HAL_PATH)/Src:$(USB_PATH)/Core/Src:$(USB_PATH)/Class/HID/Src
 
 CC      := arm-none-eabi-gcc
 LD      := arm-none-eabi-ld
@@ -10,22 +14,35 @@ OBJCOPY := arm-none-eabi-objcopy
 OBJDUMP := arm-none-eabi-objdump
 SIZE    := arm-none-eabi-size
 
-CFLAGS  = -Wall -std=gnu11 -Os -fdump-rtl-expand
+CFLAGS  = -g -Wall -std=gnu11 -Os -fdump-rtl-expand
 CFLAGS += -mlittle-endian -mcpu=cortex-m4 -mthumb
-CFLAGS += -ffunction-sections -fdata-sections
+#CFLAGS += -ffunction-sections -fdata-sections
 LDFLAGS = -nostartfiles
-LDFLAGS += -Wl,-Map=main.map -nostdlib
-LDFLAGS += -Wl,--gc-sections 
+LDFLAGS += -g -Wl,-Map=main.map -nostdlib
+#LDFLAGS += -Wl,--gc-sections 
 LIBS = -lgcc
-#LIBS += -lrdimon
 
 CFLAGS += -DSTM32F407xx
 
 LDFLAGS += -Tstm32_flash.ld
-CFLAGS += -I$(CMSIS_DEV_PATH)/Include -I$(CMSIS_PATH)/Include -I$(HAL_PATH)/Inc -Iconfig
+CFLAGS += -I$(CMSIS_DEV_PATH)/Include -I$(CMSIS_PATH)/Include -I$(HAL_PATH)/Inc -I. -Iconfig
 LDFLAGS += -L$(CMSIS_PATH)/Lib/GCC
 
-###################################################
+SOURCES = main.c keyboard.c menu.c usbh_conf.c startup_stm32f407xx.s system_stm32f4xx.c syscalls.c stm32f4xx_it.c
+SOURCES_C = $(filter %.c,$(SOURCES))
+SOURCES_ASM = $(filter %.s,$(SOURCES))
+
+CFLAGS += -I$(USB_PATH)/Core/Inc -I$(USB_PATH)/Class/HID/Inc
+USB_SOURCES := $(notdir $(wildcard $(USB_PATH)/Core/Src/*.c)) $(notdir $(wildcard $(USB_PATH)/Class/HID/Src/*.c))
+USB_SOURCES := $(filter-out usbh_conf_template.c,$(USB_SOURCES))
+
+HAL_SOURCES = stm32f4xx_hal.c
+HAL_SOURCES += stm32f4xx_hal_rcc.c stm32f4xx_hal_flash.c stm32f4xx_hal_flash_ex.c stm32f4xx_hal_dma.c
+HAL_SOURCES += stm32f4xx_hal_usart.c stm32f4xx_hal_pwr.c
+HAL_SOURCES += stm32f4xx_hal_hcd.c stm32f4xx_hal_gpio.c stm32f4xx_hal_cortex.c
+HAL_SOURCES += stm32f4xx_ll_usb.c
+
+################################################################################
 
 .PHONY: program clean
 
@@ -40,7 +57,8 @@ all: main.elf main.pdf
 %.dot: %.elf
 	r2 -a arm -qc 'aa;agC' $< 2>/dev/null >$@
 
-main.elf: main.o startup_stm32f407xx.o system_stm32f4xx.c $(HAL_PATH)/Src/stm32f4xx_ll_utils.o
+#$(HAL_PATH)/Src/stm32f4xx_ll_utils.o
+main.elf: $(SOURCES_ASM:.s=.o) $(SOURCES_C:.c=.o) $(USB_SOURCES:.c=.o) $(HAL_SOURCES:.c=.o)
 	$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $^ $(LIBS)
 	$(OBJCOPY) -O ihex $@ $(@:.elf=.hex)
 	$(OBJCOPY) -O binary $@ $(@:.elf=.bin)
diff --git a/build/.git_keep b/build/.git_keep
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/build/.git_keep
diff --git a/main.c b/main.c
index f0141f0..8b7b5c0 100644
--- a/main.c
+++ b/main.c
@@ -44,40 +44,115 @@
   *

   ******************************************************************************

   */

+

 #include "main.h"

 

+SCB_Type *scb = SCB;

+GPIO_TypeDef *gpioa = GPIOA;

+

 USBH_HandleTypeDef hUSBHost;

 HID_ApplicationTypeDef Appli_state = APPLICATION_IDLE;

 

+USART_HandleTypeDef console_uart;

+

 static void SystemClock_Config(void);

 static void USBH_UserProcess(USBH_HandleTypeDef* phost, uint8_t id);

 static void HID_InitApplication(void);

 static void Error_Handler(void);

 

+void WWDG_IRQHandler()

+{

+    while (1);

+}

+

+void uart_print(char *s)

+{

+    /* Like, there is millions of lines of perfectly useless pseudo-comments in the HAL driver. But don't think they'd

+     * say what unit that timeout parameter has in any obvious place. I'll just go with milliseconds here -.- */

+    HAL_USART_Transmit(&console_uart, (uint8_t*)s, strlen(s), 1000);

+}

+

+void uart_putc(char c)

+{

+    /* See above. */

+    HAL_USART_Transmit(&console_uart, (uint8_t*)&c, 1, 1000);

+}

+

+void HAL_USART_MspInit(USART_HandleTypeDef *narf)

+{

+    __HAL_RCC_GPIOA_CLK_ENABLE();

+    

+    /* TX */

+    GPIO_InitTypeDef pa9 = {

+        .Pin = GPIO_PIN_9,

+        .Mode = GPIO_MODE_AF_PP,

+        .Pull = GPIO_PULLUP,

+        .Speed = GPIO_SPEED_FREQ_LOW,

+        .Alternate = GPIO_AF7_USART1

+    };

+    HAL_GPIO_Init(GPIOA, &pa9);

+

+    /* RX */

+    GPIO_InitTypeDef pa10 = {

+        .Pin = GPIO_PIN_10,

+        .Mode = GPIO_MODE_AF_PP,

+        .Pull = GPIO_PULLUP,

+        .Speed = GPIO_SPEED_FREQ_LOW,

+        .Alternate = GPIO_AF7_USART1

+    };

+    HAL_GPIO_Init(GPIOA, &pa10);

+}

+

 int main(void)

 {

     HAL_Init();

     SystemClock_Config();

+    /* FIXME

     HID_InitApplication();

     USBH_Init(&hUSBHost, USBH_UserProcess, 0);

     USBH_RegisterClass(&hUSBHost, USBH_HID_CLASS);

     USBH_Start(&hUSBHost);

-

+    */

+

+    /* LEDs */

+    __HAL_RCC_GPIOA_CLK_ENABLE();

+    __HAL_RCC_USART1_CLK_ENABLE();

+    RCC->AHB1ENR  |= RCC_AHB1ENR_GPIOAEN;

+    GPIOA->MODER |=

+        (1<<GPIO_MODER_MODER6_Pos)|

+        (1<<GPIO_MODER_MODER7_Pos);

+

+    GPIOA->OSPEEDR |=

+        (2<<GPIO_OSPEEDR_OSPEED6_Pos)|

+        (2<<GPIO_OSPEEDR_OSPEED7_Pos);

+

+    USART_HandleTypeDef foo = {

+        .Instance = USART1,

+        .Init = {

+            .BaudRate = 115200,

+            .WordLength = USART_WORDLENGTH_8B,

+            .StopBits = USART_STOPBITS_1,

+            .Parity = USART_PARITY_NONE,

+            .Mode = USART_MODE_TX_RX

+        }

+    };

+    console_uart = foo;

+    HAL_USART_Init(&console_uart);

+

+    static int ticks = 0;

     while (1) {

-        USBH_Process(&hUSBHost);

-        HID_MenuProcess();

+        /* FIXME USBH_Process(&hUSBHost); */

+        /* FIXME HID_MenuProcess(); */

+        Toggle_Leds();

+        if (ticks++ == 1000000) {

+            uart_print("This is a test\r\n");

+            ticks = 0;

+        }

     }

 }

 

 static void HID_InitApplication(void)

 {

-    BSP_LED_Init(LED1);

-    BSP_LED_Init(LED2);

-    BSP_LED_Init(LED3);

-    BSP_LED_Init(LED4);

-

-    BSP_PB_Init(BUTTON_WAKEUP, BUTTON_MODE_GPIO);

-

     HID_MenuInit();

 }

 

@@ -104,97 +179,53 @@ static void USBH_UserProcess(USBH_HandleTypeDef* phost, uint8_t id)
     }

 }

 

-void Toggle_Leds(void)

-{

+void Toggle_Leds(void) {

     static uint32_t ticks;

 

-    if (ticks++ == 100) {

-        BSP_LED_Toggle(LED1);

-        BSP_LED_Toggle(LED2);

-        BSP_LED_Toggle(LED3);

-        BSP_LED_Toggle(LED4);

+    if (ticks++ == 1000000) {

+        GPIOA->ODR ^= GPIO_ODR_OD6;

+        GPIOA->ODR ^= GPIO_ODR_OD7;

         ticks = 0;

     }

 }

 

-/**

-  * @brief  System Clock Configuration

-  *         The system Clock is configured as follow :

-  *            System Clock source            = PLL (HSE)

-  *            SYSCLK(Hz)                     = 180000000

-  *            HCLK(Hz)                       = 180000000

-  *            AHB Prescaler                  = 1

-  *            APB1 Prescaler                 = 4

-  *            APB2 Prescaler                 = 2

-  *            HSE Frequency(Hz)              = 8000000

-  *            PLL_M                          = 8

-  *            PLL_N                          = 360

-  *            PLL_P                          = 2

-  *            PLL_Q                          = 7

-  *            PLL_R                          = 2

-  *            VDD(V)                         = 3.3

-  *            Main regulator output voltage  = Scale1 mode

-  *            Flash Latency(WS)              = 5

-  *         The USB clock configuration from PLLSAI:

-  *            PLLSAIM                        = 8

-  *            PLLSAIN                        = 384

-  *            PLLSAIP                        = 8

-  * @param  None

-  * @retval None

-  */

 static void SystemClock_Config(void)

 {

-    RCC_ClkInitTypeDef RCC_ClkInitStruct;

-    RCC_OscInitTypeDef RCC_OscInitStruct;

-    RCC_PeriphCLKInitTypeDef PeriphClkInitStruct;

-

     /* Enable Power Control clock */

     __HAL_RCC_PWR_CLK_ENABLE();

 

-    /* The voltage scaling allows optimizing the power consumption when the device

-     is

-     clocked below the maximum system frequency, to update the voltage scaling

-     value

-     regarding system frequency refer to product datasheet.  */

-    __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);

-

     /* Enable HSE Oscillator and activate PLL with HSE as source */

-    RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;

-    RCC_OscInitStruct.HSEState = RCC_HSE_ON;

-    RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;

-    RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;

-#if defined(USE_STM32469I_DISCO_REVA)

-    RCC_OscInitStruct.PLL.PLLM = 25;

-#else

-    RCC_OscInitStruct.PLL.PLLM = 8;

-#endif /* USE_STM32469I_DISCO_REVA */

-    RCC_OscInitStruct.PLL.PLLN = 360;

-    RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;

-    RCC_OscInitStruct.PLL.PLLQ = 7;

-    RCC_OscInitStruct.PLL.PLLR = 2;

-    if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)

+    RCC_OscInitTypeDef foo = {

+        .OscillatorType = RCC_OSCILLATORTYPE_HSE,

+        .HSEState = RCC_HSE_ON,

+        .PLL.PLLState = RCC_PLL_ON,

+        .PLL.PLLSource = RCC_PLLSOURCE_HSE,

+        /* HSE input: 8MHz */

+        .PLL.PLLM = 8,             /* VCO in: 1MHz = 8MHz / 8 */

+        .PLL.PLLN = 336,           /* VCO out: 336MHz = 1MHz * 336 */

+        .PLL.PLLP = RCC_PLLP_DIV2, /* System: 168MHz = 336Mhz / 2 */

+        .PLL.PLLQ = 7              /* USB: 48MHz = 336MHz / 7 */

+    };

+    if (HAL_RCC_OscConfig(&foo) != HAL_OK)

         Error_Handler();

 

-    /* Enable the OverDrive to reach the 180 Mhz Frequency */

-    if (HAL_PWREx_EnableOverDrive() != HAL_OK)

-        Error_Handler();

-

-    /* Select PLLSAI output as USB clock source */

-    PeriphClkInitStruct.PLLSAI.PLLSAIQ = 7;

-    PeriphClkInitStruct.PLLSAI.PLLSAIN = 384;

-    PeriphClkInitStruct.PLLSAI.PLLSAIP = RCC_PLLSAIP_DIV8;

+    /* FIXME does this require configuration?

+    RCC_PeriphCLKInitTypeDef PeriphClkInitStruct;

     PeriphClkInitStruct.PeriphClockSelection = RCC_PERIPHCLK_CK48;

     PeriphClkInitStruct.Clk48ClockSelection = RCC_CK48CLKSOURCE_PLLSAIP;

     HAL_RCCEx_PeriphCLKConfig(&PeriphClkInitStruct);

+    */

 

     /* Select PLL as system clock source and configure the HCLK, PCLK1 and PCLK2

      clocks dividers */

-    RCC_ClkInitStruct.ClockType = (RCC_CLOCKTYPE_SYSCLK | RCC_CLOCKTYPE_HCLK | RCC_CLOCKTYPE_PCLK1 | RCC_CLOCKTYPE_PCLK2);

-    RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;

-    RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;

-    RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV4;

-    RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV2;

-    if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_5) != HAL_OK)

+    RCC_ClkInitTypeDef bar = {

+        .ClockType = (RCC_CLOCKTYPE_SYSCLK | RCC_CLOCKTYPE_HCLK | RCC_CLOCKTYPE_PCLK1 | RCC_CLOCKTYPE_PCLK2),

+        .SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK,   /* See above */

+        .AHBCLKDivider = RCC_SYSCLK_DIV1,          /* 168MHz = 168MHz / 1 */

+        .APB1CLKDivider = RCC_HCLK_DIV4,           /* 42MHz = 168MHz / 4 */

+        .APB2CLKDivider = RCC_HCLK_DIV2            /* 84Mhz = 168MHz / 2 */

+    };

+    if (HAL_RCC_ClockConfig(&bar, FLASH_LATENCY_5) != HAL_OK)

         Error_Handler();

 }

 

@@ -212,3 +243,5 @@ static void Error_Handler(void)
         ;

 }

 

+void _init(void) {}

+

diff --git a/main.h b/main.h
index 948652a..4b52c38 100644
--- a/main.h
+++ b/main.h
@@ -47,11 +47,12 @@
 #ifndef __MAIN_H

 #define __MAIN_H

 

-#include "stdio.h"

 #include "usbh_core.h"

 #include "usbh_hid.h"

 #include "usbh_hid_parser.h"

 

+#include "stdio.h"

+

 typedef enum {

     HID_DEMO_START = 0,

     HID_DEMO_KEYBOARD,

@@ -81,6 +82,7 @@ typedef enum {
 extern USBH_HandleTypeDef hUSBHost;

 extern HID_ApplicationTypeDef Appli_state;

 extern HID_DEMO_StateMachine hid_demo;

+extern USART_HandleTypeDef console_uart;

 

 void Toggle_Leds(void);

 void HID_SelectItem(uint8_t** menu, uint8_t item);

@@ -89,4 +91,7 @@ void HID_MenuProcess(void);
 void HID_KeyboardMenuProcess(void);

 void USR_KEYBRD_ProcessData(uint8_t data);

 

+void uart_print(char *s);

+void uart_putc(char c);

+

 #endif

diff --git a/stm32f4xx_hal_conf.h b/stm32f4xx_hal_conf.h
index 00c13ab..16ffadd 100644
--- a/stm32f4xx_hal_conf.h
+++ b/stm32f4xx_hal_conf.h
@@ -47,24 +47,45 @@
 

 #define HAL_MODULE_ENABLED

 

+#include "stm32f4xx_hal_def.h"

+

+#define HAL_RCC_MODULE_ENABLED

+#include "stm32f4xx_hal_rcc.h"

+

+#define HAL_FLASH_MODULE_ENABLED

+#include "stm32f4xx_hal_flash.h"

+

 #define HAL_DMA_MODULE_ENABLED

 #include "stm32f4xx_hal_dma.h"

 

+#define HAL_USART_MODULE_ENABLED

+#include "stm32f4xx_hal_usart.h"

+

+#define HAL_PWR_MODULE_ENABLED

+#include "stm32f4xx_hal_pwr.h"

+

+/* USB host controller foo */

+#define HAL_HCD_MODULE_ENABLED

+#include "stm32f4xx_hal_hcd.h"

+

+/* Whoever needs a HAL for GPIOs... */

+#define HAL_GPIO_MODULE_ENABLED

+#include "stm32f4xx_hal_gpio.h"

+

+/* Why not wrap the wrapper? */

+#define HAL_CORTEX_MODULE_ENABLED

+#include "stm32f4xx_hal_cortex.h"

+

+/*

 #define HAL_DMA2D_MODULE_ENABLED

 #include "stm32f4xx_hal_dma2d.h"

 

-#define HAL_FLASH_MODULE_ENABLED

-#include "stm32f4xx_hal_flash.h"

-

 #define HAL_SRAM_MODULE_ENABLED

 #include "stm32f4xx_hal_sram.h"

 

 #define HAL_SDRAM_MODULE_ENABLED

 #include "stm32f4xx_hal_sdram.h"

 

-#define HAL_GPIO_MODULE_ENABLED

-#include "stm32f4xx_hal_gpio.h"

-

 #define HAL_I2C_MODULE_ENABLED

 #include "stm32f4xx_hal_i2c.h"

 

@@ -74,23 +95,9 @@
 #define HAL_DSI_MODULE_ENABLED

 #include "stm32f4xx_hal_dsi.h"

 

-#define HAL_PWR_MODULE_ENABLED

-#include "stm32f4xx_hal_pwr.h"

-

-#define HAL_RCC_MODULE_ENABLED

-#include "stm32f4xx_hal_rcc.h"

-

-#define HAL_UART_MODULE_ENABLED

-#include "stm32f4xx_hal_uart.h"

-

-#define HAL_CORTEX_MODULE_ENABLED

-#include "stm32f4xx_hal_cortex.h"

-

-#define HAL_HCD_MODULE_ENABLED

-#include "stm32f4xx_hal_hcd.h"

-

 #define HAL_FMPI2C_MODULE_ENABLED

 #include "stm32f4xx_hal_fmpi2c.h"

+*/

 

 #if !defined(HSE_VALUE)

 #if defined(USE_STM32469I_DISCO_REVA)

diff --git a/syscalls.c b/syscalls.c
new file mode 100644
index 0000000..023cac3
--- /dev/null
+++ b/syscalls.c
@@ -0,0 +1,190 @@
+/* Support files for GNU libc.  Files in the system namespace go here.

+   Files in the C namespace (ie those that do not start with an

+   underscore) go in .c.  */

+

+#include <_ansi.h>

+#include <sys/types.h>

+#include <sys/stat.h>

+#include <sys/fcntl.h>

+#include <stdio.h>

+#include <string.h>

+#include <time.h>

+#include <sys/time.h>

+#include <sys/times.h>

+#include <sys/errno.h>

+#include <reent.h>

+#include <unistd.h>

+#include <sys/wait.h>

+

+

+#define FreeRTOS

+#define MAX_STACK_SIZE 0x200

+

+extern int __io_putchar(int ch) __attribute__((weak));

+extern int __io_getchar(void) __attribute__((weak));

+

+#ifndef FreeRTOS

+  register char * stack_ptr asm("sp");

+#endif

+

+

+

+

+caddr_t _sbrk(int incr)

+{

+	extern char end asm("end");

+	static char *heap_end;

+	char *prev_heap_end,*min_stack_ptr;

+

+	if (heap_end == 0)

+		heap_end = &end;

+

+	prev_heap_end = heap_end;

+

+#ifdef FreeRTOS

+	/* Use the NVIC offset register to locate the main stack pointer. */

+	min_stack_ptr = (char*)(*(unsigned int *)*(unsigned int *)0xE000ED08);

+	/* Locate the STACK bottom address */

+	min_stack_ptr -= MAX_STACK_SIZE;

+

+	if (heap_end + incr > min_stack_ptr)

+#else

+	if (heap_end + incr > stack_ptr)

+#endif

+	{

+//		write(1, "Heap and stack collision\n", 25);

+//		abort();

+		errno = ENOMEM;

+		return (caddr_t) -1;

+	}

+

+	heap_end += incr;

+

+	return (caddr_t) prev_heap_end;

+}

+

+/*

+ * _gettimeofday primitive (Stub function)

+ * */

+int _gettimeofday (struct timeval * tp, struct timezone * tzp)

+{

+  /* Return fixed data for the timezone.  */

+  if (tzp)

+    {

+      tzp->tz_minuteswest = 0;

+      tzp->tz_dsttime = 0;

+    }

+

+  return 0;

+}

+void initialise_monitor_handles()

+{

+}

+

+int _getpid(void)

+{

+	return 1;

+}

+

+int _kill(int pid, int sig)

+{

+	errno = EINVAL;

+	return -1;

+}

+

+void _exit (int status)

+{

+	_kill(status, -1);

+	while (1) {}

+}

+

+int _write(int file, char *ptr, int len)

+{

+	int DataIdx;

+

+		for (DataIdx = 0; DataIdx < len; DataIdx++)

+		{

+		   __io_putchar( *ptr++ );

+		}

+	return len;

+}

+

+int _close(int file)

+{

+	return -1;

+}

+

+int _fstat(int file, struct stat *st)

+{

+	st->st_mode = S_IFCHR;

+	return 0;

+}

+

+int _isatty(int file)

+{

+	return 1;

+}

+

+int _lseek(int file, int ptr, int dir)

+{

+	return 0;

+}

+

+int _read(int file, char *ptr, int len)

+{

+	int DataIdx;

+

+	for (DataIdx = 0; DataIdx < len; DataIdx++)

+	{

+	  *ptr++ = __io_getchar();

+	}

+

+   return len;

+}

+

+int _open(char *path, int flags, ...)

+{

+	/* Pretend like we always fail */

+	return -1;

+}

+

+int _wait(int *status)

+{

+	errno = ECHILD;

+	return -1;

+}

+

+int _unlink(char *name)

+{

+	errno = ENOENT;

+	return -1;

+}

+

+int _times(struct tms *buf)

+{

+	return -1;

+}

+

+int _stat(char *file, struct stat *st)

+{

+	st->st_mode = S_IFCHR;

+	return 0;

+}

+

+int _link(char *old, char *new)

+{

+	errno = EMLINK;

+	return -1;

+}

+

+int _fork(void)

+{

+	errno = EAGAIN;

+	return -1;

+}

+

+int _execve(char *name, char **argv, char **env)

+{

+	errno = ENOMEM;

+	return -1;

+}

diff --git a/system_stm32f4xx.c b/system_stm32f4xx.c
index d00e5aa..fc979ef 100644
--- a/system_stm32f4xx.c
+++ b/system_stm32f4xx.c
@@ -119,7 +119,7 @@ void SystemCoreClockUpdate(void)
     case 0x04: /* HSE */

         SystemCoreClock = HSE_VALUE;

         break;

-    case 0x08: /* PLL */

+    case 0x08: {/* PLL */

         /* PLL_VCO = (HSE_VALUE or HSI_VALUE / PLL_M) * PLL_N

            SYSCLK  = PLL_VCO / PLL_P */

         uint32_t pllvco;

@@ -132,13 +132,12 @@ void SystemCoreClockUpdate(void)
 

         uint32_t pllp = (((RCC->PLLCFGR & RCC_PLLCFGR_PLLP) >> 16) + 1) * 2;

         SystemCoreClock = pllvco / pllp;

-        break;

+        break; }

     default:

         SystemCoreClock = HSI_VALUE;

         break;

     }

     /* Compute HCLK frequency */

-    tmp = AHBPrescTable[((RCC->CFGR & RCC_CFGR_HPRE) >> 4)];

-    SystemCoreClock >>= tmp;

+    SystemCoreClock >>= AHBPrescTable[((RCC->CFGR & RCC_CFGR_HPRE) >> 4)];

 }