由于目前.Net Micro Framework并不支持P/Invoke功能(也无法像WinCE一样开发流式驱动),所以在底层在驱动层面用C直接对存储器(Flash)进行文件系统开发是行不通的。幸好.Net Micro Framework提供了ExtendedWeakReference类,其中赋值Target对象可以把数据存放到存储器上(Flash)。
[Serializable]
private class FlashDatas
{
//调入数据
public static byte[] Load(uint index)
{
ExtendedWeakReference ewr = ExtendedWeakReference.RecoverOrCreate(
typeof(FlashDatas), //类型,任意类都可以,其名称起到一个索引作用
index, //ID号,这个数据比较有用,不同ID号代表不同数据
ExtendedWeakReference.c_SurviveBoot);//该标志和.c_SurviveBoot 区别不大
return ewr.Target as byte [];
}
//保存数据
public static void Save(uint index, byte [] data)
{
ExtendedWeakReference ewr = ExtendedWeakReference.RecoverOrCreate(typeof (FlashDatas), index, ExtendedWeakReference.c_SurviveBoot);
ewr.Target = data;
}
}
private class FlashDatas
{
//调入数据
public static byte[] Load(uint index)
{
ExtendedWeakReference ewr = ExtendedWeakReference.RecoverOrCreate(
typeof(FlashDatas), //类型,任意类都可以,其名称起到一个索引作用
index, //ID号,这个数据比较有用,不同ID号代表不同数据
ExtendedWeakReference.c_SurviveBoot);//该标志和.c_SurviveBoot 区别不大
return ewr.Target as byte [];
}
//保存数据
public static void Save(uint index, byte [] data)
{
ExtendedWeakReference ewr = ExtendedWeakReference.RecoverOrCreate(typeof (FlashDatas), index, ExtendedWeakReference.c_SurviveBoot);
ewr.Target = data;
}
}
上面的代码就是ExtendedWeakReference类的具体使用,从代码可以看出我们无法直接对存储器进行读写,只能通过保存类的方式对数据进行存储,至于该数据存放到何处,那是无从得知的。
我最初的想法是定义一个类,类中定义一个大数组,不过实际调试发现,该数组不能太大,超过几十K就会出现内存溢出。幸好该对象可以是字节数组,所以我产生了另一个想法,每次保存一个512字节大小的字节数组,相当于磁盘上的一个扇区,以此为存取的最小单位,实现FAT文件系统。
在我博客上曾写了一篇关于FAT文件系统的文章,如《FAT文件系统几点释疑》(
http://blog.csdn.net/yefanqiu/archive/2008/03/13/2176340.aspx
),我们知道要实现FAT16系统一般至少需要4M存储空间,实现FAT32一般需要256M空间以上。所以我简单的做了一个程序,在实际硬件中测试一下存取1024*4个512字节的数组内存是否可行。
测试代码如下:
private const uint SectorSize=512; //扇区大小
private const uint SecPerClus = 4; //一个簇包含的扇区数
public static void Main()
{
Debug.Print("Start" );
for (uint i = 0; i < 512; i++) //1024*4
{
byte[] bytData = new byte [SectorSize];
bytData[0] = (byte)(i % 256 );
bytData[bytData.Length - 1] = bytData[0 ];
FlashDatas.Save(i, bytData);
Debug.Print(i.ToString() + " Save " + bytData[0].ToString() + " " + bytData[bytData.Length - 1 ].ToString());
// byte[] bytData = FlashDatas.Load(i);
// if (bytData == null)
// {
// Debug.Print(i.ToString() + " Load Error");
// break;
// }
// else
// {
// Debug.Print(i.ToString() + " Load " + bytData[0].ToString() + " " + bytData[bytData.Length - 1].ToString());
//}
}
Debug.Print("Exit" );
}
private const uint SecPerClus = 4; //一个簇包含的扇区数
public static void Main()
{
Debug.Print("Start" );
for (uint i = 0; i < 512; i++) //1024*4
{
byte[] bytData = new byte [SectorSize];
bytData[0] = (byte)(i % 256 );
bytData[bytData.Length - 1] = bytData[0 ];
FlashDatas.Save(i, bytData);
Debug.Print(i.ToString() + " Save " + bytData[0].ToString() + " " + bytData[bytData.Length - 1 ].ToString());
// byte[] bytData = FlashDatas.Load(i);
// if (bytData == null)
// {
// Debug.Print(i.ToString() + " Load Error");
// break;
// }
// else
// {
// Debug.Print(i.ToString() + " Load " + bytData[0].ToString() + " " + bytData[bytData.Length - 1].ToString());
//}
}
Debug.Print("Exit" );
}
让我失望的是,Digi的开发板存储个数一旦超过128个就会出现读失败,新拿来的iPac-9302开发板要好一些,512个之内读写没有什么问题,超过这个数就会出现和Digi开发板一样的问题。需要说明的时,在使用读写的过程中如果不断电,读写都会成功的。一但断电重新读取,读就会失败。(当然在我测试过程中出现了各种各样不同的现象,如只能成功读取前几个)。
杜伟当初还想直接支持FAT32系统呢,目前恐怕FAT16的支持都很困难了,如果实现FAT12系统就有点不值当了。不过杜伟建议说模拟器也支持数据存储功能,所以先在模拟器中实现该功能。
没有想到,模拟器存储器最大存储仅支持1M,开始我还以为我配置参数不当呢,后来反编译了模拟器相关的核心代码,发现1M在代码中就已经写死了,相关内容如下。
反编译 Microsoft.SPOT.Emulator.dll,下面是关键代码
------------------------------------------------------------------------
//内存大小0x10000*16 = 1024*1024 也就是1M空间。
public class
FlashManager : MemoryManagerBase
{
// Fields 存储空间已经写死,就是1M
private FlashSector[] _flashSectors = new FlashSector[] {
new FlashSector(0x10000 , FlashSectorUsage.Log, FlashSectorPartition.Start),
new FlashSector(0x10000 , FlashSectorUsage.Log, FlashSectorPartition.None),
new FlashSector(0x10000 , FlashSectorUsage.Log, FlashSectorPartition.None),
new FlashSector(0x10000 , FlashSectorUsage.Log, FlashSectorPartition.None),
new FlashSector(0x10000 , FlashSectorUsage.Log, FlashSectorPartition.None),
new FlashSector(0x10000 , FlashSectorUsage.Log, FlashSectorPartition.None),
new FlashSector(0x10000 , FlashSectorUsage.Log, FlashSectorPartition.None),
new FlashSector(0x10000 , FlashSectorUsage.Log, FlashSectorPartition.End),
new FlashSector(0x10000 , FlashSectorUsage.Log, FlashSectorPartition.Start),
new FlashSector(0x10000 , FlashSectorUsage.Log, FlashSectorPartition.None),
new FlashSector(0x10000 , FlashSectorUsage.Log, FlashSectorPartition.None),
new FlashSector(0x10000 , FlashSectorUsage.Log, FlashSectorPartition.None),
new FlashSector(0x10000 , FlashSectorUsage.StorageA, FlashSectorPartition.None),
new FlashSector(0x10000 , FlashSectorUsage.StorageA, FlashSectorPartition.None),
new FlashSector(0x10000 , FlashSectorUsage.StorageB, FlashSectorPartition.None),
new FlashSector(0x10000 , FlashSectorUsage.StorageB, FlashSectorPartition.End) };
....
}
//分配内存
internal override void AllocateMemory()
{
this .ValidateFlashSectorsInternal();
uint num = 0 ;
for (int i = 0; i < this._flashSectors.Length; i++ )
{
num += this ._flashSectors[i].Length;
}
base._size = num;
base.AllocateMemory(); //分配内存 ... ...
for (int j = 0; j < base._size; j++ )
{
base._memory[j] = 0xff ;
}
this .InitializeFlashSectorsInternal();
}
//分配内存
internal virtual void AllocateMemory()
{
this._memory = new byte[this ._size];
this._handle = GCHandle.Alloc(this._memory, 3 );
}
{
// Fields 存储空间已经写死,就是1M
private FlashSector[] _flashSectors = new FlashSector[] {
new FlashSector(0x10000 , FlashSectorUsage.Log, FlashSectorPartition.Start),
new FlashSector(0x10000 , FlashSectorUsage.Log, FlashSectorPartition.None),
new FlashSector(0x10000 , FlashSectorUsage.Log, FlashSectorPartition.None),
new FlashSector(0x10000 , FlashSectorUsage.Log, FlashSectorPartition.None),
new FlashSector(0x10000 , FlashSectorUsage.Log, FlashSectorPartition.None),
new FlashSector(0x10000 , FlashSectorUsage.Log, FlashSectorPartition.None),
new FlashSector(0x10000 , FlashSectorUsage.Log, FlashSectorPartition.None),
new FlashSector(0x10000 , FlashSectorUsage.Log, FlashSectorPartition.End),
new FlashSector(0x10000 , FlashSectorUsage.Log, FlashSectorPartition.Start),
new FlashSector(0x10000 , FlashSectorUsage.Log, FlashSectorPartition.None),
new FlashSector(0x10000 , FlashSectorUsage.Log, FlashSectorPartition.None),
new FlashSector(0x10000 , FlashSectorUsage.Log, FlashSectorPartition.None),
new FlashSector(0x10000 , FlashSectorUsage.StorageA, FlashSectorPartition.None),
new FlashSector(0x10000 , FlashSectorUsage.StorageA, FlashSectorPartition.None),
new FlashSector(0x10000 , FlashSectorUsage.StorageB, FlashSectorPartition.None),
new FlashSector(0x10000 , FlashSectorUsage.StorageB, FlashSectorPartition.End) };
....
}
//分配内存
internal override void AllocateMemory()
{
this .ValidateFlashSectorsInternal();
uint num = 0 ;
for (int i = 0; i < this._flashSectors.Length; i++ )
{
num += this ._flashSectors[i].Length;
}
base._size = num;
base.AllocateMemory(); //分配内存 ... ...
for (int j = 0; j < base._size; j++ )
{
base._memory[j] = 0xff ;
}
this .InitializeFlashSectorsInternal();
}
//分配内存
internal virtual void AllocateMemory()
{
this._memory = new byte[this ._size];
this._handle = GCHandle.Alloc(this._memory, 3 );
}
此外模拟器在运行结束时,不能保证执行重载的UninitializeComponent函数,所以无法保存内存的数据,代码如下。
/// <summary>
/// Called by the emulator after all components were setup and registered
/// </summary>
public override void InitializeComponent()
{
base .InitializeComponent();
_form = new YFEmulatorForm(this .Emulator);
_form.OnInitializeComponent();
//Launch the UI thread.
Thread uiThread = new Thread(RunForm);
uiThread.SetApartmentState(ApartmentState.STA);
uiThread.Start();
//读Flash数据
EmulatorFlashPersistance.Load(this );
//必须添加这句,否则不会执行UninitializeComponent方法
Application.DoEvents(); //这是我添的
}
/// <summary>
/// Called by the emulator after the program exits
/// </summary>
public override void UninitializeComponent() //这个函数不能保证会运行
{
//保存数据
EmulatorFlashPersistance.Save(this); //所以无法保存最后的结果
Application.DoEvents(); //保存数据
base .UninitializeComponent();
// When the Micro Framework is shutting down, inform the the WinForm application
//to exit as well.
Application.Exit();
}
/// Called by the emulator after all components were setup and registered
/// </summary>
public override void InitializeComponent()
{
base .InitializeComponent();
_form = new YFEmulatorForm(this .Emulator);
_form.OnInitializeComponent();
//Launch the UI thread.
Thread uiThread = new Thread(RunForm);
uiThread.SetApartmentState(ApartmentState.STA);
uiThread.Start();
//读Flash数据
EmulatorFlashPersistance.Load(this );
//必须添加这句,否则不会执行UninitializeComponent方法
Application.DoEvents(); //这是我添的
}
/// <summary>
/// Called by the emulator after the program exits
/// </summary>
public override void UninitializeComponent() //这个函数不能保证会运行
{
//保存数据
EmulatorFlashPersistance.Save(this); //所以无法保存最后的结果
Application.DoEvents(); //保存数据
base .UninitializeComponent();
// When the Micro Framework is shutting down, inform the the WinForm application
//to exit as well.
Application.Exit();
}
目前该工作的开展对我来说,实在是一个不小的挑战。由于国内研究.Net Micro Framework不多,不仅没有人进行深层次的讨论,也少见相关资料,所以.Net Micro Framework推广真是任重而道远啊。
附记:在我上两篇关于串口部署的文章又有了新的进展,最近花了300多元购买了Moxa的UPort1110 USB转串口设备(一般的杂牌子的设备大约几十元一个)还真不错,在我笔记本上终于可以直接通过串口对.Net Micro Framework进行调试了。