Open Flash loader template (OFL)

Flash loader template without the need for a Keil/Segger DSK license. OFL uses cmake and arm-none-eabi to build. OFL uses parts of klib

Create a Flash loader executable

To create a OFL executable you need the following:

• A driver for the peripheral the memory is connected to
• A driver to communicate with the flash memory
• Way to feed the watchdog if enabled
• A way to restore modified registers after deinit

⚠️ When using the flash loader no startup code will run. Make sure to initialize any (non const) static and global variables at runtime as they will not be initialized when loading the flash loader.

Stack usage

In the current documentation Segger mentions they reserve 512 bytes for a Open flash loader stack with a fallback to 256 bytes for devices with low amount of memory. The previous versions reserved 256 bytes of memory. By default the linkerscript allocates 256 bytes of stack for testing.

Interrupts

by default the J-link will disable the global interrupts when starting a flash loader. If your flash loader needs interrupts (not recommended) the user will need to move the interrupt vector table during init (and revert it when deiniting)

Create a flash loader xml file

SEGGER J-Link uses xml files to add support for external loaders. The xml file configures the follwing:

• The target Microcontroller for the loader
• The address the memory is located
• What executable file to load
• The name it shows up as in the J-Link software

Example xml file for the LPC1756 is25lq040b open flash loader.

<DataBase>
    <Device>
        <ChipInfo Vendor="NXP" Name="LPC1756" />
        <FlashBankInfo Name="NOR Flash" BaseAddr="0xA0000000">
            <LoaderInfo Name="SPI flash loader" MaxSize="0x01000000" Loader="flash_loader.elf" LoaderType="FLASH_ALGO_TYPE_OPEN" />
        </FlashBankInfo>
    </Device>
</DataBase>

More info can be found at https://wiki.segger.com/J-Link_Device_Support_Kit

Installing your open flash loader

There are 2 ways to install your open flash loader

1. Manually copying the executable and xml to %appdata%/SEGGER/JlinkDevices/vendor/device_family
2. Using a installer (like open flashloader installer)

Example

A example is available for the LPC1756 and is25lq040b. Made using the drivers from: klib.