The Yamaha E3 (or DKC-850) firmware update is wonderfully simple, unlike its older Mark IV sibling. The entire update can be done using just a USB stick with at least 20MB of memory.
In October of 2020, Yamaha mandated that its pianos use better encryption standards (all pianos now use TLS 1.2 instead of TLS 1.1). If you connected your piano to the internet before October of 2020, it probably automatically updated to the latest firmware. However, if you weren’t so lucky, you’ll have to perform the updates yourself.
First, you’ll need to download a copy of the new firmware, and you’ll need a USB stick.
You can obtain this either by downloading the Yamaha E3 v3.54 file (dkv_update.bin) from my MEGA drive, or you can visit Yamaha’s website for an archived copy. Once you have the dkv_update.bin file, simply copy it on a USB stick (not in any directories or folders). Take that USB stick and insert it into your Disklavier. Now hold down the Play / Pause button and power on the system (with the Play / Pause button still held). From there, you can follow the on-screen instructions.
If you have any difficulties, I’ve attached a PDF of their instructions below. You’ll need to start with “Downloading the Update Program using a PC and USB Flash Memory” on page three.