For Windows: Open device manager Find Unknown “Android” device (likely listed under Other devices with an exclamation mark) Update driver Browse my computer for driver software Let me pick from a list of devices, select List All Devices Under “Android device” or “Google Inc”, you will find “Android Bootloader Interface” Choose “Android Bootloader Interface” Click … Read more
The short version of the page linked by D Shu (and without the horrible popover ads) is that this “waiting for device” problem happens when the USB device node is not accessible to your current user. The USB id is different in fastboot mode, so you can easily have permission to it in adb but … Read more
What works for me is to kill and start the adb server again. On linux: sudo adb kill-server and then sudo adb start-server. Then it will detect nearly every device out of the box.