【.Net Micro Framework PortingKit - 06】设置芯片时钟

上两篇《修改启动代码&重写向量表》《SRAM初始化&设置NVIC中断表偏移》文章中，我们设置了中断向量表，初始化了RAM，并重设了向量表的地址，本篇文章是相对重要的一篇，我们将设置芯片时钟。

1、新建CortexM3.h头文件

在.\DeviceCode\Targets\Native\CortexM3目录中新建 CortexM3.h文件，并编写如下代码：

#ifndef _CORTEXM3_H_

#define _CORTEXM3_H_1

#include <cores\arm\include\cpu.h>

typedef volatile unsigned long VU32;

typedef volatile unsigned short VU16;

typedef volatile unsigned char VU8;

extern "C"

{

void BootstrapCode_Clocks();

}

/*------------------------ Reset and Clock Control ---------------------------*/

struct CortexM3_RCC

{

static const UINT32 c_Base = 0x40021000;

static const UINT8 FLAG_HSIRDY = ((UINT8)0x20);

static const UINT8 FLAG_HSERDY = ((UINT8)0x31);

/****/ volatile UINT32 CR;

static const UINT32 CR_HSEBYP_Reset = ((UINT32)0xFFFBFFFF);

static const UINT32 CR_HSEBYP_Set = ((UINT32)0x00040000);

static const UINT32 CR_HSEON_Reset = ((UINT32)0xFFFEFFFF);

static const UINT32 CR_HSEON_Set = ((UINT32)0x00010000);

static const UINT32 CR_HSITRIM_Mask = ((UINT32)0xFFFFFF07);

/****/ volatile UINT32 CFGR;

static const UINT32 CFGR_SYSCLK_Div1 = ((UINT32)0x00000000);

static const UINT32 CFGR_SYSCLK_Div2 = ((UINT32)0x00000080);

static const UINT32 CFGR_SYSCLK_Div4 = ((UINT32)0x00000090);

static const UINT32 CFGR_SYSCLK_Div8 = ((UINT32)0x000000A0);

static const UINT32 CFGR_SYSCLK_Div16 = ((UINT32)0x000000B0);

static const UINT32 CFGR_HCLK_Div1 = ((UINT32)0x00000000);

static const UINT32 CFGR_HCLK_Div2 = ((UINT32)0x00000400);

static const UINT32 CFGR_HCLK_Div4 = ((UINT32)0x00000500);

// 省略部分代码 .....

/****/ volatile UINT32 APB1RSTR;

/****/ volatile UINT32 AHBENR;

/****/ volatile UINT32 BDCR;

/****/ volatile UINT32 CSR;

static void Initialize();

static bool GetFlagStatus(UINT8 Flag);

};

struct CortexM3

{

static CortexM3_RCC & RCC() { return *(CortexM3_RCC *)(size_t)(CortexM3_RCC::c_Base); }

};

#endif // _CORTEXM3_H_1

2、编写BootStrap代码

我们从.\DeviceCode\Drivers\Stubs\Processor\stubs_bootstrap目录到.\DeviceCode\Targets\Native\CortexM3\DeviceCode,并修改目录的名字为BootStrap，下一步我们在BootStrap.cpp文件编写如下代码：

#include <tinyhal.h>

#include "..\CortexM3.h"

//--//

#pragma arm section code = "SectionForBootstrapOperations"

void __section(SectionForBootstrapOperations) CortexM3_RCC::Initialize (void)

{

CortexM3_RCC &RCC = CortexM3::RCC();

// RCC system reset(for debug purpose)

/* Set HSION bit */

RCC.CR |= (UINT32)0x00000001;

/* Reset SW[1:0], HPRE[3:0], PPRE1[2:0], PPRE2[2:0], ADCPRE[1:0] and MCO[2:0] bits */

RCC.CFGR &= (UINT32)0xF8FF0000;

/* Reset HSEON, CSSON and PLLON bits */

RCC.CR &= (UINT32)0xFEF6FFFF;

// 省略部分代码 .....

/* Enable GPIOA, GPIOB, GPIOF, GPIOG and AFIO clocks */

RCC.APB2ENR |= CortexM3_RCC::APB2RSTR_GPIOA | CortexM3_RCC::APB2RSTR_GPIOB | CortexM3_RCC::APB2RSTR_GPIOF |CortexM3_RCC::APB2RSTR_GPIOG |CortexM3_RCC::APB2RSTR_AFIO;

}

bool __section(SectionForBootstrapOperations) CortexM3_RCC::GetFlagStatus(UINT8 Flag)

{

UINT32 tmp = 0;

UINT32 statusreg = 0;

CortexM3_RCC &RCC = CortexM3::RCC();

/* Get the RCC register index */

tmp = Flag >> 5;

if (tmp == 1) /* The flag to check is in CR register */

{

statusreg = RCC.CR;

}

else if (tmp == 2) /* The flag to check is in BDCR register */

{

statusreg = RCC.BDCR;

}

else /* The flag to check is in CSR register */

{

statusreg = RCC.CSR;

}

/* Get the flag position */

tmp = Flag & ((UINT8)0x1F);

return ((statusreg & ((UINT32)1 << tmp)) != 0);

}

void __section(SectionForBootstrapOperations) BootstrapCode_Clocks()

{

CortexM3_RCC::Initialize();

}

extern "C"

{

void __section(SectionForBootstrapOperations) BootstrapCode()

{

BootstrapCode_Clocks();

}

}

#pragma arm section code

3、修改.\Solutions\STM3210E\NativeSample\NativeSample.proj文件

在NativeSample.proj文件中作如下修改：

<ItemGroup>

<RequiredProjects Include="$(SPOCLIENT)\DeviceCode\Targets\Native\CortexM3\DeviceCode\stubs_bootstrap\dotNetMF.proj" />

<DriverLibs Include="cpu_bootstrap_stubs.$(LIB_EXT)" />

</ItemGroup>

修改为：

<ItemGroup>

<RequiredProjects Include="$(SPOCLIENT)\DeviceCode\Targets\Native\CortexM3\DeviceCode\BootStrap\dotNetMF.proj" />

<DriverLibs Include="BootStrap.$(LIB_EXT)" />

</ItemGroup>

4、编译修改并调试运行，我想这次会有很大的成就感，因为LED闪烁的节奏明显的加快了，我们的CPU在高速运行了！

即将过去的2010年的前三天，对我来说是辛苦的三天，平均每天工作16个小时以上，不仅编写了相关代码，还写了以上六篇文章。希望我的这些努力能点燃.Net Micro Framework爱好者心中的热情，动起手来一起移植.Net Micro Framework，其实这对自己的嵌入式开发功力的提高也大有裨益。明天就要上班了，我将又回到开发Wifi相关接口的工作上来，后续的文章我想只有到下周末才能相见了，到那时我们将编写串口驱动，系统的一些调试信息将可以通过串口传输给PC机上的串口调试程序，这一步将是关键的一步，非常值得的期待，希望我能顺利完成这步工作！