Where to download?
For YI 4K+ Action Camera, see below for download links:
Check out the following image.Where is SN?
How to update firmware?
Download the firmware to the SD card root directory, change the file name to be “firmware.bin", then put the SD card into the device, follow the update pop-up in the LCD. (Make sure the camera is connected to a power source or has more than 50% battery life.)