Hardwares to boost phyphox

[d.girardi]

Hi guys, 
I found this work about use the headphone jack as an external port on smartphone. With a simple circuit they can measure external temperature (through microfone amplitude) and dc voltage (see reference 5) through microfone frequence. 
Next week I will try this circuits with phyphox and post my results here. 

https://www.researchgate.net/publication...n_cookbook

[Sebastian Staacks]

While I appreciate the simplicity of effectively wiring the audio output to the audio input, I am afraid that this requires a calibration for each phone as I would expect that the output and input levels differ. So, for sensors that easily work across devices, digital communication (i.e. BLE) is preferable but requires more complex electronics, while this audio jack method is ingeniously simple to build for a single device.