That WARNING sounds serious. How did you test your design without risking your Amiga hardware? - echolevel/open-amiga-sampler GitHub Wiki

For initial diagnostics, to establish exactly how the samplers' inputs were being addressed by the Amiga but without risking any possibility of causing a short on an Amiga's parallel port, we used a Teensy 3.5 dev board (similar to an Arduino but a bit more powerful and flexible) to emulate what we thought was happening and see how the samplers responded. We also read a lot of very old and badly scanned datasheets from the 1980s and spent a lot of time with a multimeter and a serial monitor. We needed to not only work out how e.g. the Techno Sound Turbo worked, but also how different variations of the 'cheap sampler' design were able to be addressed generically by non-proprietary software packages (e.g. Protracker, which works with almost any sampler, as opposed to software packages that came bundled with specific samplers and sometimes allowed custom functionality to be used).

We used the Teensy 3.5 rather than the 3.6 because its data pins are 5v tolerant for input, even though the Teensy itself runs at and outputs 3.3v signals. This is important because the Amiga's parallel port outputs a +5v reference voltage that powers the sampler's chips, and so the signals that are returned on the data pins are also in the 5v range. Also, because all Teensy boards have 3.3v output pins, we needed to use a multi-channel logic level converter board to convert all our control signals (STROBE, PAPER_OUT and SELECT) to 5v. Conveniently, the sampler and the logic level converter can be powered from the Teensy's 5v USB input supply.

Another reason to use the Teensy 3.5 is that it has a built-in SD card, so we're able to write incoming data bytes to a raw file as signed 8bit values (in the range of -128 to 127), and then convert these files to WAV to check whether they sound...anything like they're supposed to. For a while, friends, they absolutely did not! But then we gradually figured out everything we were doing wrong and got it working.

And yes, similar to the way the Amiga reads from the sampler, our Teensy code has a fast loop (the main loop with some 5 and 40 microsecond delays to approximate the sample rate we wanted) and feeds the samplers a sensible rate of STROBE pulses that cause it to return useful amplitude values.