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

Note: 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 previous documentation Segger mensioned they reserve 256 bytes of stack for Open flash loaders. In newer versions the documentation mentions 512 bytes of stack with a fallback to 256 bytes for devices with low amounts of memory (for testing, the linkerscript configures 256 bytes of stack).

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.