Accessing Memory Mapped Registers from Windows Compact-7 Eboot

This post covers accessing Memory Mapped Register from Windows Compact 7 BSP

When I was debugging one of the peripheral in Eboot, we are not sure about the sequence of initialization as the documentation on the hardware is little and we also had very little support from the vendor.

Given this scenario if we modify a single bit in a register do the following for each iteration

• Build the EBoot Module
• Insert SD Card into Card Reader
• Copy binaries to SD Card 
• Safe Remove from PC
• Reinsert into target Micro-SD Slot
• Wait for Eboot to boot
• Check the Register Values by dumping them

This process has eaten out most of our time.

Then we thought of having a Eboot menu in which we can read and write to Memory Mapped Registers. 

For this we have followed below steps

1. Implement RegRead function
2. Implement RegWrite funciton
3. Implement OALStringToHex
4. Create a menu for the Register Utility
5. Add the Utility to Eboot Main Menu

The code that I wrote is directly given below for reference

For RegRead

VOID  RegRead
(
OAL_BLMENU_ITEM *pMenu
)
{
    WCHAR  szVal[9];
UINT32 u32RegAddr;

    OALLog(L"\r\n Enter Register Address: ");

    if (OALBLMenuReadLine(szVal, dimof(szVal)) == 0)
        {
        goto cleanUp;
        }

    u32RegAddr = OALStringToHex(szVal);

OALMSG (1,(L"\r\n\tReg Addr:0x%08x Val:0x%08x\r\n",
u32RegAddr, *((DWORD *)u32RegAddr)));
cleanUp:
    return;
}

For RegWrite

For this function we need to take two inputs. The first one is Register Address and the second input  is Register Value. The source code for the same is given below.


VOID  RegWrite
(
OAL_BLMENU_ITEM *pMenu
)
{
    WCHAR  szVal[9];
UINT32 u32RegAddr;
UINT32 u32RegVal;

    OALLog(L"\r\n Enter Register Address: ");

    if (OALBLMenuReadLine(szVal, dimof(szVal)) == 0)
        {
        goto cleanUp;
        }

    u32RegAddr = OALStringToHex(szVal);

    OALLog(L"\r\n Enter Register Value: ");

    if (OALBLMenuReadLine(szVal, dimof(szVal)) == 0)
        {
        goto cleanUp;
        }

    u32RegVal = OALStringToHex(szVal);

OALMSG (1,(L"\r\n\tWriting to Register Addr:0x%08x Val:0x%08x\r\n",
u32RegAddr, u32RegVal));
*((DWORD *)u32RegAddr) = u32RegVal;

cleanUp:
    return;
}

OALStringtoHex

The String to hex conversion function has to convert string to hex and it is left for the readers to write themselves.

Creating Menu for Register Utility


static OAL_BLMENU_ITEM  g_menuRegisterUtilities[] = {
    {
        L'1', L"Write Reg", RegWrite,
        NULL, NULL, NULL
    }, {
        L'2', L"Read Reg", RegRead,
        NULL, NULL, NULL
    }, {
        L'0', L"Exit and Continue", NULL,
        NULL, NULL, NULL
    }, {
        0, NULL, NULL,
        NULL, NULL, NULL
    }
};


Adding Register Utility Menu to Main Menu

Please add below lines before Exit and Continue of the Eboot Main Menu

    }, {
L'R', L"Register Utility Menu", OALBLMenuShow,
        L"Register Utility Menu", &g_menuRegisterUtilities, NULL

Note: Please do remember to remove this option while shipping the products.

Thank You for reading the post.

Careful with watchdog timer

OS: Windows CE 6.0 R3
Platform: OMAP3530 EVM

I was debugging one of the driver present in OMAP3530 BSP provided by some vendor some time ago. So, the driver is compiled with COMPILE_DEBUG option so that I can keep breakpoints and see what are the issues with the driver. As soon as the control hits break point I was looking at the variables in watch window. All of a sudden the processor starts rebooting. After two days at last when  we are looking at the catalog items we observed that Watch Dog Catalog item has been selected from BSP.

Just make a note that we have to disable Watch Dog Timer when the software needs debugging with breakpoints.

Happy Debugging.