App note: Implement capacitive sensing on a PIC10F microcontroller

Here’s an app note from Microchip describing how to implement capacitive sensing using two pins on the tiny PIC10F microcontroller.

Capacitive sensing is implemented by turning the comparator into a relaxation oscillator. The output of the comparator is used to charge and discharge the sensing capacitor, that is formed by a pad on the circuit board. The charge rate is determined by the RC time constant, created by an external resistor and the capacitance of the pad.

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  1. Actually they’re using two pins for the sensing, not a “single hey” :-)

    I did a quick comparison if this solution compared to use one of the Atmel dedicated touch sensors. It turns out that you need the same number of external parts, both chips are available as SOT-23 and the cost for both of them are ~0.58 cents in 100 qty.

    A negative point with the Pic10F-solution is that you need to flash them with the firmware before you can use them, but this is also a positive thing since you can adapt and tune the software better to your particular usage case. And if you need many of them you can have Microchip flash them at the factory for a few cents extra.

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