After experimenting some time with an alternative to rebuild a rubber-version Spectrum keyboard membrane from scratch, I wanted to do the same with the Plus membrane. The philosophy is the same, but the making was too hard: the Plus membrane has not two, but four circuits and two inner layers to isolate them. This is necesary to be able to simulate the closing of two independent circuits with a single key operation.

First prototype. Note that there are only three lines that are used in the connector back Spectrum: 5V, ground, and the reset signal, we use because the uC has the ability to reset the Spectrum from the keyboard (yes, with the famous three-finger-salute: D)

As it's time to build the board, it may seem difficult to solder the microcontroller, which is a 32 pin QFP device. Actually it's not that hard, and it only requires a thin solder tip (1 mm). This is how the uC looks like one it is solded to the PCB.

New features for firmware version 1.3!!

Ben Versteeg is currently working on an external version based upon my original PS/2 keyboard adapter design. Being external means that it will be succesfully used both with the ZX Spectrum+, and with every other Speccy model. Besides, if you don't use more than a Spectrum at a time, you can have one of this, and plug it in the Speccy you want to use. Internal keyboard is not disabled during operation.

Ben's design allows for other peripherals to be used, as it adds a pass-through connector. Ben is currently accepting orders.

From firmware version 1.3, the user does not need a special programmer to update the firmware inside the microcontroller. He only needs his Spectrum, the PS/2 interface adapter, and a working PC keyboard attached to it.

Maybe the most interesting hack is related to the posibility of changing the Spectrum program that is atomatically typed and loaded when Ctrl-Alt-F1 is pressed. In this article, which will be updated to reflect other available firmware hacks, I will explain how to do this.