Fwd: Adding a system management MPU

[Wolfgang Spraul]

fyi

Begin forwarded message:

> From: Milosch Meriac <meriac at openmoko.org>
> Date: March 19, 2008 6:53:43 AM GMT+08:00
> Subject: Re: Adding a system management MPU
>
> Andy Green wrote:
>> There is a plan to basically put the debug board FTDI chip on the
>> mainboard for JTAG / debrick purposes, along with a micro USB conn  
>> that
>> isn't accessible without opening the case.  So we discard the debug
>> board as a "product" and all phones expose a "USB UART" console and  
>> JTAG
>> if you want it.
>
> I would fear the added cost of the FTDI chip - it's also ugly to  
> force the user to open the case.
> In terms if de-bricking I could imagine to expose the RFCOMM- 
> interface of the Bluetooth chip
> I decided in my EBook design to stick to a discrete CSR Bluecore4  
> chip with UART + USB interface. To debrick it you would for example  
> hold a given set of keys that are anyway connected to the MSP and  
> use MSP to set the ARM-core into UART boot mode (from ARM core mask  
> ROM)after resetting it. The MSP will then upload the stepstone over  
> UART into the internal SRAM of your main ARM CPU.
>
> This stepstone in turn would accept XMODEM image over UART that is  
> routed from RFCOMM/BLuetooth to the main CPU and write page-per-page  
> into NAND/NOR flash. Naturally the main image can also be loaded  
> over SDCARD (the MSP430 sees if a SDCARD is inserted via IO pin).  
> The advantage would be that the case will stay closed and no  
> additional chip or special de-bricking software is needed. The UART- 
> Steptone can be easily stored inside the MSP internal flash (guess  
> 2K is mork than enough for this task). For de-bricking even  
> Hypterterminal or cu (uucp package) would be sufficient.
>
>
> Warmest regards,
> --
> Milosch
>
>

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