Is it possible to sleep and wake up a device with rui_device_sleep (using RAK compiler) without the help of any external source? I mean, by only using an internal watch dog? I would like to send a measure one time per hour.
Sure, it is possible. You can use rui_device_sleep API to do it.
Actually, you can think RUI APIs as another format AT command which is used in internal, no need external source, so if any function AT commands can do, RUI APIs can do surely.