am 3359 beaglebone black baremetal assembly programming

I get this on the console if i try to see what' s in memory using memory viewer : "CortxA8: Trouble Writing Memory Block at 0x44E0713C on Page 0 of Length 0x4: (Error -1065 @ 0x44E0713C) Unable to access device memory" and "CortxA8: Trouble Writing Memory Block at 0x44e0713c on Page 0 of Length 0x4: (Error -1065 @ 0x44E0713C) Unable to access device memory."

Hi Sanket,

You are trying to access the GPIO0_DATAOUT register, right? Probably some initialization is missing. I suggest you download the Starterware software package and use it as a starting point for writing baremetal code: http://www.ti.com/tool/starterware-sitara

yes that's right. i need to initialize the GPIO control register. but since i want to be output pin its reset value does the part for me.

sanket borhade said:

So i pressed SW2 on the board while powering it so it skips the internal booting and waits for SD card which i haven't inserted. This way i tried to avoid booting Uboot. I also created empty project using code composer studio v5.5 and following is the code that i used in the file main_code.S

Now i also have debugger BlackHawk USB 100v2 and have selected same in project properties.

If you create a target configuration for the "BeagleBone_Black" board:

It should select a gel file to initialize the hardware:

Is there a GEL file in your target  configuration?

yes, it does have gel file. I also checked the contents of the file and it says this :

OnTargetConnect()
{
    GEL_MapOff();
    GEL_MapReset();
    GEL_MapAddStr(0x00020000, 0, 0x0000C000, "R", 0);    // Boot ROM
    GEL_MapAddStr(0x08000000, 0, 0x01000000, "R|W", 0);  // 16MB GPMC External/NOR (on GP Daughtercard)
    GEL_MapAddStr(0x40020000, 0, 0x0000C000, "R", 0);    // Boot ROM (also at 0x20000)
    GEL_MapAddStr(0x402F0400, 0, 0x0000FC00, "R|W", 0);  // SRAM Internal
    GEL_MapAddStr(0x40300000, 0, 0x00010000, "R|W", 0);  // OCMC-RAM
    GEL_MapAddStr(0x44000000, 0, 0x00400000, "R|W", 0);  // L3F CFG Regs
    GEL_MapAddStr(0x44800000, 0, 0x00400000, "R|W", 0);  // L3S CFG Regs
    GEL_MapAddStr(0x44C00000, 0, 0x00400000, "R|W", 0);  // L4_WKUP
    GEL_MapAddStr(0x46000000, 0, 0x00400000, "R|W", 0);  // McASP0 Data
    GEL_MapAddStr(0x46400000, 0, 0x00400000, "R|W", 0);  // McASP1 Data
    GEL_MapAddStr(0x47400000, 0, 0x00005000, "R|W", 0);  // USB0/1
    GEL_MapAddStr(0x47810000, 0, 0x00010000, "R|W", 0);  // MMCHS2
    GEL_MapAddStr(0x48000000, 0, 0x01000000, "R|W", 0);  // L4 PER
    GEL_MapAddStr(0x49000000, 0, 0x00B00000, "R|W", 0);  // EDMA
    GEL_MapAddStr(0x4A000000, 0, 0x01000000, "R|W", 0);  // L4_FAST
    GEL_MapAddStr(0x4C000000, 0, 0x01000000, "R|W", 0);  // EMIF
    GEL_MapAddStr(0x50000000, 0, 0x01000000, "R|W", 0);  // GPMC Regs
    GEL_MapAddStr(0x56000000, 0, 0x01000000, "R|W", 0);  // SGX530
    GEL_MapAddStr(0x80000000, 0, 0x20000000, "R|W", 0);  // 512MB DDR3 external memory
    GEL_MapOn();
    AM335xStartState();
    AM335x_BeagleBlack_Initialization();
    Disable_Watchdog();

}

from this i can see that address of the GPIO's are already given "R/W" access. but still i cannot read them from the code.

sanket borhade said:

from this i can see that address of the GPIO's are already given "R/W" access. but still i cannot read them from the code

[The same applies for the CM_WKUP_GPIO1_CLKCTRL .. CM_WKUP_GPIO3_CLKCTRL registers for GPIO1 to GPIO3]

As Biser Gatchev-XID has already suggested, look at the StarterWare software package to see how that enables and uses the GPIO modules.

thanks for the reply. The example using starterWare to blink user LED on the board works fine. But its C program in the end. I need it to be done using simple ARM Assembly. So i tried to do the same process as the sample example does in Assembly, since i am not able to access the memory location of the GPIO registers i cannot enable the CLK of the module. I hope you are getting my question. (I do not want any C code in my project just Assembly programming).

It's great you've got the c-code blinky program working. I would suggest your next step might be to look at the C code startup file to see how they do all their initial setup.

Thanks, i will try this out and share the results.
I have connected separate external LED's on GPIO0 for testing.

Good luck!

Final word of caution:  do be very careful with the GPIO_OE register.  The am335x pinmux (unlike that of e.g. the dm814x) doesn't have a "safe mode" and configures most pins to GPIO by default.  I think this is an unfortunate design choice made by TI.  While this saves you from having to do any pin setup to get your LED or other GPIO working, it also means that if you make a mistake in GPIO_OE you end up driving the wrong pin(s), hence risk hardware damage.

I tried the way you suggested. I could see the contains of GPIO atleast on debugger register view by modifying the CM_WLK_GPIO0_CTRL register. But beaglebone's AM3359 is not giving access through code.
it skips the code steps (one that you mentioned to modify register and checking the bits) and console shows error that you cannot access readonly memory locations.

I modified the contains from CCS windows by clicking on the same and i could modify it. Then what is stopping it from doing it through code?
I am still not sure whether i can bypass the linux booting? I would really appreciate if someone suggest method to avoid booting linux.

probably, that is rejecting the access to these registers!