Implement Flash configuration

drivers/flash.c

@@ -0,0 +1,47 @@
+/** @file flash.c
+ * Module handling flash memory interface registers.
+ *
+ * The module provides functions to configure the flash and perform read and
+ * writes
+ */
+
+//--includes--------------------------------------------------------------------
+
+#include "flash.h"
+#include "flash_regs.h"
+
+
+//--local definitions-----------------------------------------------------------
+
+//--local variables-------------------------------------------------------------
+
+static volatile struct FLASH* regs = (struct FLASH*)FLASH_BASE_ADDRESS;
+
+
+//--public functions------------------------------------------------------------
+
+void flash_configure(enum FlashPreset preset)
+{
+	//restore default configuration
+	regs->ACR.word &= !0x3f;
+	regs->ACR.word |= 0x30;
+
+	//apply new configuration
+	switch (preset) {
+		case FLASH_PRESET_LOW_CLOCK_SPEED:
+			regs->ACR.HLFCYA = 0x1; //half cycle for power saving
+			break;
+		case FLASH_PRESET_MEDIUM_CLOCK_SPEED:
+			regs->ACR.LATENCY = 0x1;
+			break;
+		case FLASH_PRESET_HIGH_CLOCK_SPEED:
+			regs->ACR.LATENCY = 0x2;
+			break;
+		default:
+			break;
+	}
+}
+
+
+//--local functions-------------------------------------------------------------
+

drivers/flash.h

@@ -0,0 +1,39 @@
+/** @file flash.h
+ * Module handling flash memory interface registers.
+ *
+ * The module provides functions to configure the flash and perform read and
+ * writes
+ */
+
+#ifndef _FLASH_H_
+#define _FLASH_H_
+
+//--includes--------------------------------------------------------------------
+
+#include "stdint.h"
+
+
+//--type definitions------------------------------------------------------------
+
+/**
+ * Available flash configuration presets
+ */
+enum FlashPreset {
+	FLASH_PRESET_LOW_CLOCK_SPEED,    //for 0 < clock <= 24Mz
+	FLASH_PRESET_MEDIUM_CLOCK_SPEED, //for 24MHz < clock <= 48MHz
+	FLASH_PRESET_HIGH_CLOCK_SPEED,   //for 48MHz < clock <= 72MHz
+};
+
+
+//--functions-------------------------------------------------------------------
+
+/**
+ * Configure the flash according to the given preset. Warning: calling this
+ * function with a sysclk higher than 24Mhz may cause the system to crash,
+ * please lower the clocks first
+ */
+void flash_configure(enum FlashPreset preset);
+
+
+#endif //_FLASH_H_
+

drivers/rcc.c

@@ -9,6 +9,7 @@
 
 #include "rcc.h"
 #include "rcc_regs.h"
+#include "flash.h"
 
 
 //--local definitions-----------------------------------------------------------
@@ -78,6 +79,9 @@ static void apply_default_preset(void)
 	regs->CIR.HSIRDYIE = 0x0;
 	regs->CIR.HSERDYIE = 0x0;
 	regs->CIR.PLLRDYIE = 0x0;
+
+	//reconfigure flash
+	flash_configure(FLASH_PRESET_LOW_CLOCK_SPEED);
 }
 
 /**
@@ -116,9 +120,8 @@ static void apply_speed_preset(void)
 	regs->CFGR.PPRE1 = 0x4;  // /2
 	regs->CFGR.ADCPRE = 0x2; // /6
 
-	//configure flash
+	//reconfigure flash
-	volatile uint32_t* ACR = (uint32_t*)0x40022000;
+	flash_configure(FLASH_PRESET_HIGH_CLOCK_SPEED);
-	*ACR |= 0x12;
 
 	//switch to PLL output
 	regs->CFGR.SW = 0x2;