In May 1985 it was announced an interface for the ZX Spectrum that can control Robotix's motor joints with BASIC.
My brother found a Robotix kit in a second hand market, and now I'm wondering if that interface ever existed or if can be built somehow.
It seems that an interface for the BBC Micro was available in 1986. I don't have time to read the whole article right now, but from the images it seems something that you have to build with solder and a few components. I examined the kit I have and it seems anyway that the motors are driven by switches. I'm quite confident that with an Arduino or a Raspberry Pi and a few relays switches I could drive them.
Now there's a wave of nostalgia, I'd completely forgotten about Robotix, had a set myself way back in the 80's. Never knew you could hook it up to a Speccy, though it was still great fun.