Diff: PLL_Config.c

Revision:

0:7088bc4c9949

diff -r 000000000000 -r 7088bc4c9949 PLL_Config.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/PLL_Config.c	Thu May 31 19:30:01 2018 +0000
@@ -0,0 +1,54 @@
+#include <stm32f4xx.h>
+
+void PLL_Config(void)
+{
+    
+
+//*******************************************************************************
+//*            PLL (clocked by HSI) used as System clock source                 *
+//*                         By Stuart MacVeigh                                  *
+//*******************************************************************************
+
+    RCC->APB1ENR |= RCC_APB1ENR_PWREN;  //enable power interface clock source
+    PWR->CR |= PWR_CR_VOS;
+
+    
+        #define PLL_N   180         //SYSTEM CLOCK SPEED (FCY (MHz))
+        #define HSI     16000000    //INTERAL OSC FREQUENCY
+        
+        #define PLL_M   (HSI/2000000)       //Fcy = Fxtal x PLL_N/(PLL_P x PLL_M)
+        #define PLL_P   2
+        #define PLL_Q   7
+    // HCLK = SYSCLK / 1
+    RCC->CFGR |= RCC_CFGR_HPRE_DIV1;        //CORE CLOCK = 180MHZ
+    
+    // PCLK2 = HCLK / 2
+    RCC->CFGR |= RCC_CFGR_PPRE2_DIV4;       //PERIPHERAL CLOCK 2 = 180MHZ/4 = 45MHZ, THIS IS BECAUSE THE SPI MODULES (AND POSSIBLY OTHERS) DO NOT OPERATE PROPERLY WHEN PCLK > 42MHZ
+    
+    // PCLK1 = HCLK / 4
+    RCC->CFGR |= RCC_CFGR_PPRE1_DIV4;       //PERIPHERAL CLOCK 1 = 180MHZ/4 = 45MHZ, THIS IS BECAUSE THE SPI MODULES (AND POSSIBLY OTHERS) DO NOT OPERATE PROPERLY WHEN PCLK > 42MHZ
+
+    // Configure the main PLL
+    RCC->PLLCFGR = PLL_M | (PLL_N << 6) | (((PLL_P >> 1) -1) << 16) | (PLL_Q << 24);
+
+    // Enable the main PLL
+    RCC->CR |= RCC_CR_PLLON;
+
+    // Wait till the main PLL is ready
+    while(!(RCC->CR & RCC_CR_PLLRDY));
+   
+    // Configure Flash prefetch, Instruction cache, Data cache and wait state
+    FLASH->ACR = FLASH_ACR_ICEN |FLASH_ACR_DCEN |FLASH_ACR_LATENCY_5WS;
+
+    // Select the main PLL as system clock source
+    RCC->CFGR &=~ RCC_CFGR_SW;
+    RCC->CFGR |= RCC_CFGR_SW_PLL;
+
+    // Wait till the main PLL is used as system clock source
+    while ((RCC->CFGR & RCC_CFGR_SWS ) != RCC_CFGR_SWS_PLL);
+    
+//******************************************************************************
+//*            END PLL (CLOCKED BY HSI) SETUP CODE                             *
+//******************************************************************************
+    
+}