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Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
@Gordon
@Tobbe - that's exactly what I do with the two-directional comms - hence why the characters appear pretty quickly. I left it out of the one-directional examples to make the code simpler.
And yes, just for reliability. 1V would probably be ok, but then a lot of devices turn the volume down when you plug headphones in, so getting the maximum output possible does help with that.
Also, as you send data, the capacitor discharges. If you transmitted 0V to -1V and were sending a 50% duty cycle wave then the capacitor would charge such that -0.5V went to the potential divider's voltage. That means you've then only got 0.5v left, which is too close to 0.4v for comfort.