Trying to use the Adafruit UF2 bootloader so that in my product I can drag & drop new firmware images

Question

Hi

On Github I have found https://github.com/adafruit/Adafruit_nRF52_Bootloader and at https://github.com/adafruit/Adafruit_nRF52_Bootloader/tree/master/src/boards I have found a release image for pca10056 devkit at https://github.com/adafruit/Adafruit_nRF52_Bootloader/releases

The release image contains the softdevice.

I think that the bootloader leverages the Nordic MBR so the softdevice starts at 0x1000.
The secondary uf2 bootloader is at the top end of the flash space.

I have built my application to start at 0x1000 as I don't need the softdevice as I plan to leverage the Zephyr based stack.
When I load that application using the debugger I do not get to my main().

BTW: I loaded the UF2 bootlaoder release image HEX file using Programmer launched from nRF Connect for DEsktop v4.1.2 and I did complain that there was content beyond the flash size and I notice that the hex file writes to 0x10001014 which I recall from my Laird days is the start address where the bootloader jumps to.
It must have programmed it, because when I plug the USB of the nrf52840 into my PC I do get a flash drive appear (I disconnected the cable from the Segger chip usb just to be sure I was seeing the correct flash drive).

As a sanity check, I am now going to try and build my image at the end of the SD to see if it fires up into my app.

I will be most grateful for any assistance, and if it is from non-Nordic developers I am even will to pay for the help :-)

I look forward to hearing from anyone out there.

KInd regards
Mahendra

PS: in a previous job I worked on nordic BLE since 2012 to 2020 so not a newbie and in the early days I even developed my own bootloader.

paul · Answer

I had a similar issue on a 'adafruit_feather_nrf52840' board, also described in this devzone post.

I believe the issue is the default Zephyr memory map collides with the Adafruit bootloader layout (see diagram here).

So, I modified the dts file like this:

&flash0 {

	partitions {
		compatible = "fixed-partitions";
		#address-cells = <1>;
		#size-cells = <1>;

		sd_partition: partition@0 {
			label = "softdevice";
			reg = <0x00000000 0x00026000>;
		};
		slot0_partition: partition@26000 {
			label = "image-0";
			reg = <0x00026000 0x00067000>;
		};

		/* Storage partition will be used by FCB/NFFS/NVS if enabled. */
		storage_partition: partition@e5000 {
			label = "storage";
			reg = <0x000e5000 0x00008000>;
		};
	};
};

And then added these to my prj.conf:

CONFIG_BUILD_OUTPUT_UF2=y
CONFIG_USE_DT_CODE_PARTITION=y

At the end of the 'west build' line, the uf2 start address matches the dts:

Converting to uf2, output size: 415744, start address: 0x26000
Wrote 415744 bytes to zephyr.uf2

And now I'm able to load the uf2 file successfully via drag-and-drop. Hope that helps!

Trying to use the Adafruit UF2 bootloader so that in my product I can drag & drop new firmware images

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