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Using a Nunchuck with the HomeBrew Gen3 (HBG3)

The "Nunchuck" is a game controller device originally designed for the Nintendo Wii system. It has a dual-axis thumbstick as well as two buttons, labelled Z and C.

The HBG3 has two modes of operation for the Nunchuck, described below. Push-and-hold both buttons for a couple of seconds (blue LED will flash on HBG3) to change between Modes 1 and 2. The current mode is saved in NVRAM and survives resets and power-cycles.

Mode 1. Slew+Focus Mode:

The thumbstick slews the mount by default.
Holding in the Z button while slewing gives a higher speed range.
Holding in the C button instead moves a Celestron compatible Focus Motor, if present.

Mode 2. Focus-only mode:

The thumbstick moves only the Focus Motor. The buttons are used to remember and return Focus to "preset" or "saved" focus positions. Push-and-hold either single button to memorize the current focus position (blue LED will flash on HBG3). Later, tap that same button to cause the Focus Motor to return to the saved position. This can be useful when switching between eyepieces that have different focus properties. Presets are saved in NVRAM, so they survive resets and power-cycles.

Focus and Slewing speeds:

All motion with the Nunchuck is variable speed, based upon how far from centre the thumbstick is moved. With the Focus Motor, the Up-Down axis gives a higher variable speed range than the Left-Right axis. For slewing the mount, one can hold in the Z button for a higher speed range.

a RED Nunchuck plugged into HBG3

Where to get a Nunchuck

Amazon. $10 or less, and better than the "real" Nintendo branded ones!
Maybe about one in every five is a bad one; just return it and get another!
White, Pink, and Red are the best colours; black isn't a great choice for dark locations..