I want to send some Data to my Arduino by using the audio jack of my smartphone/computer. (USB is no option, since my smartphone does not support USB Host mode and I also don't want to go wireless or use a modem)
I have allready connected my computer to my Arduino and created a squarewave as the audio signal. But what the Arduino saw, was something like the derivative of the squarewave. Or a declining voltage of capacitor. I haven't lookt at it at a high enough sampling rate to specify this. (I didn't use an amplificator)
What do I have to do, to get the Arduino to read 0 and 1, like the signal I created?