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 Post subject: Force RomBOOT to skip directly to SAM-BA Boot
PostPosted: Wed May 25, 2011 6:49 pm 
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Joined: Thu Feb 24, 2011 5:26 pm
Posts: 11
I'm using a at91sam9g20 CPU on a project and the hardware we produced did not provide a jumper on the NAND Chip Select the way the EK board is designed. I made slight modifications to the at91bootstrap and for some reason the check for BP4 is not executing allowing me to clear out the boot strap code. I am not unable to connect SAM-BA to flash the device, receiving the typical "No valid processor ID found" message. I know this is due to RomBOOT finding a valid image in the NAND and jumping to it.

Is there any way to force RomBOOT to skip directly to the SAM-BA Boot sequence and not follow the flow diagram in the AT91SAM9G20 Preliminary document (Figure 13-1)?


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 Post subject: Re: Force RomBOOT to skip directly to SAM-BA Boot
PostPosted: Wed May 25, 2011 7:23 pm 
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Joined: Wed Jan 09, 2008 5:09 pm
Posts: 186
Location: Mounds View, MN
I think the only thing you can do is short the pull-up resistor on the NAND FLash CE line when you power the unit. I use a metal tweezers to do that that as a quick and dirty way to disable the NAND Flash.

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Tim Barr
Multitech Inc.


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 Post subject: Re: Force RomBOOT to skip directly to SAM-BA Boot
PostPosted: Wed May 25, 2011 9:18 pm 
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Joined: Sat Oct 30, 2010 6:04 pm
Posts: 574
You can provide it a valid bootable device higher up the list. Like an MMC/DataFlash type device.

You can connect via JTAG, reset, halt and step through the code. You could breakpoint it at the boot probing stage, and jump to the SAM-BA entry point instead of going through the list.

You might be able to use/configure something like JFlashARM to manage the NAND via JTAG


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 Post subject: Re: Force RomBOOT to skip directly to SAM-BA Boot
PostPosted: Wed May 25, 2011 11:47 pm 
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Joined: Thu Feb 24, 2011 5:26 pm
Posts: 11
I was able to erase the the flash using JLink. For anyone who needs it I did the following.

I created an elf binary that erases NAND Block 0

// eraser_app
int main()
{
hw_init();
nandflash_hw_init();
AT91F_NandEraseBlock0();
return 0;
}

I then started JLink, halted the CPU, loaded my app into memory and ran it.

J-Link> usb 0
J-Link> h
J-Link> loadbin eraser_app.elf 0x20000
J-Link> setpc 0x20000
J-Link> g

Power cycled the board and all I get is RomBOOT. Not the greatest fix, but at least I won't have more dead boards.


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