NUCLEO-F411RE USB clock frequency fix

HAL: NUCLEO_F411RE - Corrected USB clock frequency

Modified the main PLL settings so that the USB clock will run at a proper 48MHz instead of 44.44MHz. Consequently, the core clock will now run at 96MHz instead of 100MHz.

Author: neilt6

libraries/mbed/targets/cmsis/TARGET_STM/TARGET_STM32F4/TARGET_NUCLEO_F411RE/system_stm32f4xx.c

@@ -27,15 +27,15 @@
   *                                    | 2- PLL_HSE_XTAL        |
   *                                    | (external 8 MHz xtal)  |
   *-----------------------------------------------------------------------------
-  * SYSCLK(MHz)                        | 100                    | 100
+  * SYSCLK(MHz)                        | 96                     | 96
   *-----------------------------------------------------------------------------
-  * AHBCLK (MHz)                       | 100                    | 100
+  * AHBCLK (MHz)                       | 96                     | 96
   *-----------------------------------------------------------------------------
-  * APB1CLK (MHz)                      | 50                     | 50
+  * APB1CLK (MHz)                      | 48                     | 48
   *-----------------------------------------------------------------------------
-  * APB2CLK (MHz)                      | 100                    | 100
+  * APB2CLK (MHz)                      | 96                     | 96
   *-----------------------------------------------------------------------------
-  * USB capable (48 MHz precise clock) | NO                     | NO
+  * USB capable (48 MHz precise clock) | YES                    | YES
   *-----------------------------------------------------------------------------  
   ******************************************************************************
   * @attention
@@ -611,22 +611,22 @@ uint8_t SetSysClock_PLL_HSE(uint8_t bypass)
   RCC_OscInitStruct.PLL.PLLState        = RCC_PLL_ON;
   RCC_OscInitStruct.PLL.PLLSource       = RCC_PLLSOURCE_HSE;
   //RCC_OscInitStruct.PLL.PLLM          = 8;             // VCO input clock = 1 MHz (8 MHz / 8)
-  //RCC_OscInitStruct.PLL.PLLN          = 400;           // VCO output clock = 400 MHz (1 MHz * 400)
+  //RCC_OscInitStruct.PLL.PLLN          = 384;           // VCO output clock = 384 MHz (1 MHz * 384)
   RCC_OscInitStruct.PLL.PLLM            = 4;             // VCO input clock = 2 MHz (8 MHz / 4)
-  RCC_OscInitStruct.PLL.PLLN            = 200;           // VCO output clock = 400 MHz (2 MHz * 200)
-  RCC_OscInitStruct.PLL.PLLP            = RCC_PLLP_DIV4; // PLLCLK = 100 MHz (400 MHz / 4)
-  RCC_OscInitStruct.PLL.PLLQ            = 9;             // USB clock = 44.44 MHz (400 MHz / 9) --> Not good for USB
+  RCC_OscInitStruct.PLL.PLLN            = 192;           // VCO output clock = 384 MHz (2 MHz * 192)
+  RCC_OscInitStruct.PLL.PLLP            = RCC_PLLP_DIV4; // PLLCLK = 96 MHz (384 MHz / 4)
+  RCC_OscInitStruct.PLL.PLLQ            = 8;             // USB clock = 48 MHz (384 MHz / 8) --> Good for USB
   if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
   {
     return 0; // FAIL
   }
 
   /* 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; // 100 MHz
-  RCC_ClkInitStruct.AHBCLKDivider  = RCC_SYSCLK_DIV1;         // 100 MHz
-  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;           //  50 MHz
-  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;           // 100 MHz
+  RCC_ClkInitStruct.SYSCLKSource   = RCC_SYSCLKSOURCE_PLLCLK; // 96 MHz
+  RCC_ClkInitStruct.AHBCLKDivider  = RCC_SYSCLK_DIV1;         // 96 MHz
+  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;           // 48 MHz
+  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;           // 96 MHz
   if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_3) != HAL_OK)
   {
     return 0; // FAIL
@@ -665,22 +665,22 @@ uint8_t SetSysClock_PLL_HSI(void)
   RCC_OscInitStruct.PLL.PLLState        = RCC_PLL_ON;
   RCC_OscInitStruct.PLL.PLLSource       = RCC_PLLSOURCE_HSI;   
   //RCC_OscInitStruct.PLL.PLLM          = 16;            // VCO input clock = 1 MHz (16 MHz / 16)
-  //RCC_OscInitStruct.PLL.PLLN          = 400;           // VCO output clock = 400 MHz (1 MHz * 400)
+  //RCC_OscInitStruct.PLL.PLLN          = 384;           // VCO output clock = 384 MHz (1 MHz * 384)
   RCC_OscInitStruct.PLL.PLLM            = 8;             // VCO input clock = 2 MHz (16 MHz / 8)
-  RCC_OscInitStruct.PLL.PLLN            = 200;           // VCO output clock = 400 MHz (2 MHz * 200)
-  RCC_OscInitStruct.PLL.PLLP            = RCC_PLLP_DIV4; // PLLCLK = 100 MHz (400 MHz / 4)
-  RCC_OscInitStruct.PLL.PLLQ            = 9;             // USB clock = 44.44 MHz (400 MHz / 9) --> Not good for USB
+  RCC_OscInitStruct.PLL.PLLN            = 192;           // VCO output clock = 384 MHz (2 MHz * 192)
+  RCC_OscInitStruct.PLL.PLLP            = RCC_PLLP_DIV4; // PLLCLK = 96 MHz (384 MHz / 4)
+  RCC_OscInitStruct.PLL.PLLQ            = 8;             // USB clock = 48 MHz (384 MHz / 8) --> Good for USB
   if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
   {
     return 0; // FAIL
   }
 
   /* 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; // 100 MHz
-  RCC_ClkInitStruct.AHBCLKDivider  = RCC_SYSCLK_DIV1;         // 100 MHz
-  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;           //  50 MHz
-  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;           // 100 MHz
+  RCC_ClkInitStruct.SYSCLKSource   = RCC_SYSCLKSOURCE_PLLCLK; // 96 MHz
+  RCC_ClkInitStruct.AHBCLKDivider  = RCC_SYSCLK_DIV1;         // 96 MHz
+  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;           // 48 MHz
+  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;           // 96 MHz
   if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_3) != HAL_OK)
   {
     return 0; // FAIL