.nb0 Files

Files with NB0 extension are primarily the ROM foot print. 

We would be referring to primary bootloader for a AM335x processor. The first 4-Bytes of the image contains a jump to location address which is nothing but equals to 4K offset from the starting location.

The nb0 image also contains a ROM Signature "CECE", ROM TOC Pointer offset which is at an offset of 0x44 and ROM TOC Offset which is at a offset of 0x48.

The advantage of nb0 file is it can be downloaded to SRAM present on device and the Program Counter can be set to the starting address of the image. After wards either we can do step debugging to see which instruction is causing issues to boot the device from X-Loader and then we can trace back to the C source code.

Sleep + GetTickCount

In this article I will discuss one of the problem that I was facing with Sleep API

I had written a small piece of code which is shown below

START OF CODE

DWORD dwCnt, dwCurTick;

dwCurTick = GetTickCount();

for(dwCnt = 0; dwCnt < 100; dwCnt++)
{

    Sleep(2); 

}

RETAILMSG (1,(L"Tick Diff:%d\r\n",GetTickCount()-dwCurTick));

END

I was expecting Tick Diff:200 since we kept Sleep(2) for hundred times. But the result is seen as 300.

When we modify the code as given below
 
START OF CODE

DWORD dwCnt, dwCurTick;

for(dwCnt = 0; dwCnt < 100; dwCnt++)
{
    dwCurTick = GetTickCount();

    Sleep(2); 

    RETAILMSG (1,(L"Tick Diff:%d\r\n",GetTickCount()-dwCurTick));
}

END

Result:Tick Diff:3 is printed for hundred times.

START OF CODE

DWORD dwCnt, dwCurTick;

dwCurTick = GetTickCount();while(GetTickCount() - dwCurTick <= 200);
RETAILMSG (1,(L"Tick Diff:%d\r\n",GetTickCount()-dwCurTick));

END
Result: Tick Diff:201

So for accurate Tick Delays use the GetTickCount API.

Delay in Showing Windows Compact 7 Desktop Screen

We have created a new OS Design for our custom device.

The OS that we used is Windows Compact 7.

As part of the bring up process we are not adding all the catalog items but required catalog items only are added.

Somehow the touch driver got included and it takes almost 3 minutes to show up the Windows Compact 7 desktop. When we build a debug build it shows that TOUCH PROXY Driver is looking for something for 3 minutes.

When we add the BSP_NOTOUCH the display is shown quickly.

Some differences between Windows CE and Windows Desktop

The below table shows the some of the differences that I have thought of between Windows CE and Windows Desktop.

	Windows CE	Windows Desktop
1	Componentized OS	OS is not Componentized
2	512 MB for CE 6.0 and  3GB on Windows Compact 7	4 GB assuming 32-bit processors
3	Headless	Must have a display
4	ARM, MIPS, SH4 and x86	x86 and ARM
5	RTOS	General Purpose OS
6	1mS Timer	15.6 mS Timer
7	Not based on Foreground process	Given priority to foreground process
8	Requires very less RAM order of MB	1 GB RAM
9	Order of MHz	Order of GHz
10	Less Storage Resources	More Resources
11	One root directory	Several root directories
12	Resolution of display can't be changed	Resolution can be changed at run time