https://devzone.nordicsemi.com/f/nordic-q-a/55753/how-to-do-firmware-update-on-nrf52840-through-usb-not-the-usb-with-j-linkI was checking DFU through serial usb/uart on the following link: infocenter.nordicsemi.com/index.jsp I want to double check if this entire project is for programming the nordic chip through the usb port on the long side (not the one on the shorten-USTelligent Community 13Wed, 18 Dec 2019 09:44:20 GMThttps://devzone.nordicsemi.com/thread/226075?ContentTypeID=1Wed, 18 Dec 2019 09:44:20 GMT137ad170-7792-4731-bb38-c0d22fbe4515:d0a90bc8-916f-49b1-a2f7-a7399c51b083Einar Thorsrud<p>Hi,</p> <p>Yes, the <a href="https://infocenter.nordicsemi.com/topic/sdk_nrf5_v16.0.0/sdk_app_serial_dfu_bootloader.html">example you link</a> to, is a USB bootloader. The purpose of this is to allow the programming of new firmware via the USB peripheral in the nRF52840 (connector on the long side of the DK).</p> <p>The nRF52840 ships with an empty flash, so yes: you need to program this bootloader to the nRF52840 DK via J-Link (or another SWD programmer) first. Note that you need to understand a bit about the bootloader and DFU, since you must build the bootloader with your own public key, and generate valid update images. Please see <a href="https://infocenter.nordicsemi.com/topic/sdk_nrf5_v16.0.0/lib_bootloader_dfu_process.html">Device Firmware Update process</a>.</p> <p>The nrfutil command you write is to be used with the USB bootloader that we have discussed, and therefore they should be used on the long side.</p> <p>Note that this approach could make sense in an end product, but during development, you should use the J-Link. Generally, DFU is for updating the firmware &quot;in the field&quot;.</p><div style="clear:both;"></div>