Lpc2000

Tom Walsh wrote:

>Richard Duits wrote:
>
>  
>
>>I implemented a second stage bootloader in the first flash sector that 
>>is able to update the flash via a FTDI FT245 usb link. The bootloader 
>>checks a signature (a CRC is also possible) and if this is correct, it 
>>starts the program from the second flash sector. The program can jump to 
>>a fixed address (immediately after the exception vectors) to erase the 
>>program and start an update procedure.
>>
>>If the update fails, my own bootloader in the first sector will not 
>>start the program in the second sector because of an incorrect signature 
>>or crc and it will run in update mode until a correct program is uploaded.
>>
>>A disadvantage is that you need to relocate the exception vectors to ram 
>>or use the fixed exception vector table from the bootloader. Another 
>>disadvantage is (at least with the keil ide) is that the debugger / jtag 
>>flash programmer does not know how to handle a program that does not use 
>>sector 0 which I solved by always including the bootloader code in the 
>>ide project.
>>
>> 
>>
>>    
>>
>I've done something similar.  I reserved the upper 80K of flash for use 
>of a resident bootloader.  The board has two processors: LPC2106 + 
>LPC2138.  Either processor may place the other into ISP programming mode 
>and program the other processors' flash memory.  An integral part of 
>this approach is that the SD card will always have a copy of the current 
>program of each processor.  The LPC2138 bootloader knows how to read the 
>SD filesystem.
>
>To do field updates, the end-customer replaces the two binary image 
>files and manually invokes the Update mode of the system.  The LPC2106 
>is where the Update mode would be initiated from, that processor informs 
>the LPC2138 to begin the upgrade cycle.
>
>Once the LPC2138 is told to do a system upgrade, it reprograms the IVECT 
>table (address 0) and forces a full system reset (hardware line to RESET 
>circuit).  When the LPC2138 boots, it boots into the resident loader.  
>The loader will now go through the process of erasing and reprogramming 
>the LPC2106.  After it successfully completes that, it then reprograms 
>it's main flash (all flash between the sector 0 and the resident loader 
>is erased).  When the LPC2138 main program has been programmed, as the 
>last thing, it will relocate the IVECT table into RAM and program sector 
>0.  Then the LPC2138 forces a final system reset.
>
>A bit complicated, but it does work.  I needed some way to keep special 
>software on a laptop out of the equation.  Trouble with field personnel 
>is that there is a wide disparity of technical competence when it comes 
>to computers.  Also, we wanted to keep from "owning" the laptop / 
>computer by installing our own programming software onto it.  From 
>experience, if you give the end-user a programming tool to install on 
>their Windows computer, someone will give you grief about "your software 
>screwed my computer up, tell me how to fix it!".  :(
>
>I do need to finish the bootloader scheme and have the LPC2106 processor 
>conditionally reprogram the IVECT table at sector 0 of the LPC2138.  
>This way, if the final step of the LPC2138 upgrade cycle fails (LPC2138 
>replacing vectors at sector 0), the LPC2106 can physically force another 
>cycle.  Since the two processors talk to each other over UART0, failure 
>to establish a connection within a proscribed interval would trigger this..
>
>So far, the upgrade mechanism is working ok.
>
>  
>
Just a further note.  It would be nice if we could protect a sector so 
that it would be impossible to use the IAP commands to reprogram that 
sector.  Make it a command that is only available via the ISP to lock / 
unlock protection on a specific sector.  If IAP attempts to erase / 
write that sector, it would unconditionally fail.

Philips, add that to my wish list?

TomW



-- 
Tom Walsh - WN3L - Embedded Systems Consultant
http://openhardware.net, http://cyberiansoftware.com
"Windows? No thanks, I have work to do..."
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