README.md

This is a simple bootloader for AT91SAM7256 processor located on the fpgaarcade.com replay board.

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This version was modified by W. Scherr, admin AT pin4 dot at - for replay board. See also http://fpgaarcade.com/ and http://www.pin4.at/.

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Atmel provides a bootloader called SAM-BA but as far as I can tell it is not what I want. SAM-BA takes full control of the processor: there is no provision for it to jump to a separate `application' after a few seconds. It would be possible to use their bootloader to download any kind of program to the device, but in doing so that program must wipe SAM-BA out (or else SAM-BA would never let it execute). This seems like it would be rather inconvenient for development; you would have to fiddle with the test pins to reload SAM-BA every time you wanted to download new code.

So the new bootloader works as follows:

At power-up, it is activated by pressing the menu button on the replay board. It waits about 5 seconds to see if the downloader is trying to connect via USB. Should be sufficient for Windows to set up its driver.

Afterwards the bootloader gives up control and jumps to your program. If the downloader is trying to connect, then the bootloader receives the new program over USB and writes it into flash.

Its build upon this code: http://cq.cx/at91sam7sXXX.pl (and especially the code was downloaded from here: http://cq.cx/dl/at91sam7sXXX.zip)

Credits for the original software goes to:
Jonathan Westhues, May 2006 (updated Jun 2007)
user jwesthues, at host cq.cx

I keep the license as is, also for this derivative work:

THIS SOFTWARE IS IN THE PUBLIC DOMAIN. It may therefore be used in any 
application, commercial or non-commercial, with or without attribution 
to the author. NO WARRANTY IS EXPRESSED OR IMPLIED. 

Step-by-step instructions:

0. Prerequisites:

   Compiling the code requires open-source/freeware tools only:

   • All of the ARM-side code is tested with Yagarto (arm-none-eabi, see http://www.yagarto.de/ ).
   • The downloader, which runs under Windows, is tested with Mingw (install Mingw including the MSYS development package, see here: http://www.mingw.org/wiki/Getting_Started, I used mingw-get-inst-20120426).

1. Building the bootrom:

    cd bootloader/bootrom
    make all
   

   The PID/VID are random numbers. If you intend to use this in a product, then you should at least choose different random numbers in the code.

2. Flash the created "bootrom.bin" file using bossa
   (see here: http://www.shumatech.com/web/products/bossa), sam-ba/jTag should work, too.
   Do not set the lock bit!

3. Build the downloader:

    cd ../loader
    make all
   

4. The downloader recognizes the following command line options:

    usbdl load  app.s19         -- load the application from app.s19
    usbdl bootrom bootrom.s19   -- load the bootrom from bootrom.s19
   

   It is possible to use the bootrom to load a new bootrom, even when the existing bootrom is running from flash. Of course, if something goes wrong while doing this then you will have to reload the bootrom over JTAG or SAM-BA! Don't use samba/bossa too often, it has impact on the lifetime of the NVM/flags (sets/resets the flash lock all the time).

5. Set up your application. An simple example is provided:

    cd ../app
    make all
    ../usbdl.exe load myapp.s19
   

   Then do a power cycle on the board while pressing the button.

   The memory map of the ARM's flash must be as follows:

    0x00000000                  -- bootrom
    0x00002000                  -- start of application
   

   The bootrom does the equivalent of a C function call to the start of your application; the stack will already be set up.