https://devzone.nordicsemi.com/f/nordic-q-a/60532/recommended-uart-apiHi, Our custom NRF52840 device uses a cellular modem. We communicate with this modem using AT commands. We will also be hooking up our devices to a custom server that will push FOTA updates to our devices. I am aware of two UART api&#39;s on the NRFen-USTelligent Community 13Thu, 23 Apr 2020 12:08:33 GMThttps://devzone.nordicsemi.com/thread/246252?ContentTypeID=1Thu, 23 Apr 2020 12:08:33 GMT137ad170-7792-4731-bb38-c0d22fbe4515:c22ddf71-20ba-419a-85ae-6600f965c639Edvin<p>Note: Remember that the bootloaders in our SDK require the device to push the image to the bootloader. The bootloader is a &quot;passive&quot; receiver. If your cellular modem is purely driven by AT commands, you will need to looking into a &quot;background bootloader&quot;, where you store the new image in the flash while your application is running, and then jump to the bootloader to verify the new image. That means that you have to move the transport from the bootloader to the application, and then skip right to the verification when you start the bootloader.</p> <p></p> <p>BR,</p> <p>Edvin</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/246248?ContentTypeID=1Thu, 23 Apr 2020 12:06:30 GMT137ad170-7792-4731-bb38-c0d22fbe4515:6883c0b6-cb34-4ff7-bbe7-31d882e27352Edvin<p>Hello Tim,</p> <p>I suggest you just use the app_uart. It is a simpler module, and I believe this would be well suited for what you describe here.</p><div style="clear:both;"></div>