This is day 7 of the Advent Calendar of USB keyboards. Today, an update of my previous ZX Spectrum +2 Pi builds. This one now has a USB Joystick adapter and a DC-DC converter for a more stable power supply.
This is the standard Spectrum +2 USB keyboard build, with the USB keyboard controller mounted onto the back of the keyboard. I've had trouble locating any more membrane connectors for these, so I am now using edge connectors with a plastic wedge holding the membrane tails in place. The connections are the USB cable, mode switch to change the keyboard mapping, and power LED.
Inside is a Raspberry Pi 2, and a USB Joystick and DC-DC board. This contains a relaid out version of the controller as used in my external USB joystick adapter for Atari / Commodore 9 way D joysticks.
Combined with that is power input. This was an early version of that board, where I've used a 7805 replacement DC-DC converter. I've since redesigned the board with a DC-DC converter integrated, see later in the month. No more of those little coloured squares on the top of the screen when the Pi is complaining about inadequate power supply.
I've removed two of the four USB ports on the Pi and wired them to the USB joystick and USB keyboard controllers.
That leave two USB ports and the LAN port on the rear.
The HDMI is extended to one of the spare holes in the case, and finally the mode switch button slotted in at the end.