The 4-pin JST-PH cables are a match for the trackball mouse button input. This input lets you add left-click, right-click and scroll-click buttons. The cable pinout is:

• Black - right-click
• Red - GND
• White - left-click
• Green - scroll-click

Cut the green wire off of the 4-pin JST-PH cable. Scroll-click won't be used for this project.

Cut the jumper headers off the wires and splice them.

Solder the red wire (GND) to the C pin on a NeoKey. Solder an additional shorter piece of wire to the pin as well.

Solder the white wire (left-click) to the A pin on the NeoKey. This will be the left-click key.

Solder the black wire to the second NeoKey A pin. This will be the right-click key.

Solder the shorter wire connected to the left-click NeoKey C pin to the right-click NeoKey C pin. This connects GND between the two NeoKeys.

Solder a 2-pin JST-PH socket to the two power button pins on the Raspberry Pi.

Prep a 2-pin JST-PH cable with heat shrink to solder to a button.

Solder the wires to the button leads.

Cover the leads with the heatshrink.

Plug the button into the JST-PH port on the Raspberry Pi.