The motivation to create such kind of adapter was a problem to find ready-to-solder boards for ZX Spectrum BDI. Most of them were designed for specific clones and on Ukrainian marketplaces easily accessible was only boards for Orel BK.
A bit of history...
Somewhere in 2021 I soldered Harlequin 128k and as far as I played with Tape input, decided to expand and connect disk drive. As I mentioned before, I faced mostly with BDI for Orel computer. Research had shown that all signals on the board were available on Harlequin ZXBUS Edge slot. So, I decided to give a chance and buy this adapter from one of sellers who stated that controller was tested and worked fine. Indeed, he sold DIY package with all components, so, itt was a huge plus. After I received and soldered it, another kind of issue appeared - how to connect to Harlequin. Solder by wires ZXBUS Slot? Or something else? I decided to go with adapter, on prototype board solder socket to connect controller and solder ZXBUS Slot with appropriate wiring. This idea looked more reliable then just wires.
and...
Later I expanded this adapter with optional Kempston Joystick interface, separate TRDOS rom that can in different modes and simple protection schematics for IC KP1818VG93.
The latest version looked like Frankenstien...
Over a time I collected on prototype board quite a lot of useful features and implemented them on final schematic:
- Optional Kempston Joystic, can be off, always on or depends on BETA signal from Orel BDI
- Optional ROM, can be off, only TRDOS part activated and stock ROM with Basic, TRDOS and Basic in optional ROM, in addition, 27C512 can be used without schematic changes
- Magic Button
- External +12v
- Safe +12V for 1818VG93
- Block external Kempston Joystic by /KJOY connected to A28 on ZXBUS Slot
So, I decided make it more beatuful. This is how it looks now!
