I'm using the circuit at the bottom of this post to generate a triangular wave, which I'd like to inject into a computer's microphone jack.
My computer has a single audio jack. When I plug a TRRS splitter into the jack and run a male-to-male (TRS) stereo line into the microphone side of the splitter I observe that there's 3V between the tip and the sheath as well as the ring and the sheath, while there's 0V between the tip and the ring. This suggests to me that this is a mono mic jack.
And herein lies the problem. The circuit I have looks like it requires 3 lines: ground, power, and signal. But the microphone jack looks like it only provides a power and a ground.
How can I connect adapt the circuit to drive the mic input?