I have just added a "direct" mode that does not map the spectrum keys to the ones expected from a standard PC keyboard like before. This is useless most of the time but essential to get the ZX Keyboard working with some Spectrum emulators. To enable the direct mode a hardware switch has been added to the A4. Short to ground to enable direct mode. Leave open to stick with PC emulated mode.

When active all alphanumeric keys, enter and space are directly mapped regardless of any shift buttons being pressed. Caps Shift is mapped to the left shift key and Symbol Shift to the left control key. This works with all the emulators that the original emulated PC keyboard mode.