I spent my time looking into uploading the boot loading code onto the Feather M0..

Restoring the Bootloader on the bricked Feather

Adafruit has this “step by step” guide.  This is one of the few guides on the Adafruit web site that I do not think following the steps is the best way to get to my goal – which is to reload the boot load binary code onto the Feather.  It points me on the right direction which is to get a J-Link connection to the M0 on the feather and upload the binary that way.  

I have an nRF51 DK which has a SEGGER J-Link OB debugger chip .  As I pointed out in this post, a great feature of the nRF51 DK is its debug out capability.

The question I am exploring: Can I use the nRF51 DK and SEGGER’s JLinkExe utility to upload the bootloader hex filefeatherm0bootloader_160305.zip?

to jump to the answer:


below is how I figured out the answer is NO….

Getting Ready – What JLinkExe command should I use to upload the hex file?   

JLinkExe -device ATSMD21G18

will connect me to the device over SWD (assuming I can get the connection to work). Now that the JLinkeExe utility has the right device, I should be able to upload the feather boot loader bytes with this command (assuming I’m executing the command within the same folder in which the hex file is located):

loadfile featherm0bootloader_160305.hex

Getting a J-Link Connection

Wiring up the Feather to the JLink connector is a bit of a pain because of the way the feather exposes the SWD pins:



A JLink connection requires 4 wires – in this post I discuss connecting these.  I need to solder wires to the feather’s SWD and SWC pins and connect them to these pins on the nRF51 DK.  Updated JLink commander, told JLink commander the device is a ATSMD21G18…and…


*** J-Link V6.14g J-Link V6.14g Info ***

The connected J-Link (S/N 681099822) has been designed to work with devices made by Nordic Semi only.

Debugging the selected device ATSAMD21G18 is not supported by this J-Link.


To program and debug the target device, please consider purchasing a full J-Link.

More information: <a>https://www.segger.com/jlink-debug-probes.html</a&gt;

*** J-Link V6.14g J-Link V6.14g Info ***

Oh well.  Now I know.  OK fine.  I probably will need a JLink in the future so I ordered the EDU version from Digikey.  At least it is less expensive than the last pair of shoes I bought.  Of course, I wear shoes for about 10 years….so…ok, the JLink better be useful for 10 years.