I have been using the most excellent ZXBaremulator since it was first released. I feel it the very best emulated Spectrum, due to fact it is compiled to run directly on Raspberry Pi hardware without the need for an OS. Since it was updated to include support for GPIO keyboard connection I have been using an original +2 (original grey) keyboard. The result is a machine that feels just like a hardware Spectrum, awesome. Second only to an FPGA solution like ZX-Uno or TBBLue hardware. I have been experimenting with connecting joysticks to the GPIO, recreating the 'Sinclair' joystick format. 'Sinclair' joystick interfaces essentially just 'pressed' keys for each direction and fire. Each joystick port is attached to keys "0,9,8,7.6" and "5,4,3,2,1" so it is very simple to wire up to the GPIO. For the 'Sinclair' type joystick each port uses all 5 keys from two different rows on the keyboard matrix. This is OK for most games as the 'Sinclair' joystick is a very common option. Some old games (Atic Atac) only offer 'Cursor' joystick. The cursor joystick mimicked the cursor keys on the Spectrum and used "0" for fire. This creates a problem as it spreads the keys across two keyboard rows in the matrix. You can no longer attach a common ground to a GPIO for one row.
A Solution
I soldered up a solution using Opto-couplers. Maybe someone might find this useful.
I am not an electrical engineer, so there may be a more elegant solution. This works perfectly, as evidenced by a three hour Atic Atac session..much fun (still only found 2 key sections - no POKE's used). Using ZXBaremulator and GPIO input there is zero noticeable lag at all.
I used LTV-847 4 x opto-couplers as they were in my box. On my rig I have two 9 pin d-sub's , one is wired for Sinclair joystick (port 1) the other is wired for Cursor joystick. I am a solo specchum. I could easily incorporate a switch to allow one port to swich between cursor and sinclair (port 2), maybe I will if I could encourage one of my sons to join me on Batty
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