I'm working on a prototype currently using the nRF52840 dongle. I've used the ble_app_blinky as a basic, and added some custom code to it. The goal is to use BLE in the end, but I've edited main to not do any ble at this stage. I've added support for both uarts and integrated in some of the cli demo using the usb port. So far, everything is working. Since this is based on the ble_app_blinky, the app uses s140 softdevice.
However, I've modified the behavior of the timer_handle() function.
static void timer_handle(void * p_context)