I’m interfacing an SAMD21G to a music synthesizer.
I’m using the timers to generate pulse waveforms to be used as triggers on the synthesizer.
The synth has a +12V & -12V power supply. My board has only +12V power. Synths generally deal in signals of +/-10V, and in this case I need triggers that rest at 0, and go somewhere between 7V and 10V.
I have this all working with the following circuit:Falstad circuit, image below.
BUT - If the user accidentally plugs my trigger output into a synthesizer output (which could be anywhere between +12V & -12V…) - I want my board to survive… but instead, it fried my processor… :’(
I would have thought the transistor (2N2222) and 100kΩ would have been enough…
Looking for help on how to beef up the protection here?