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Published on Feb 2, 2012
This video shows touch sensing I've made on ATtiny13.
It needs PCINT pins for interrupts (ATtiny13 got 6 of those pins) and a at least 1MOhm resistor (between PCINT pin and ground). The capacitor (made from PCB and eventually one's finger) is loaded as the PCINT pins goes 'output high' state. Then the pin is changed to 'high impedance input' and PCINT interrupt is set. Those interrupts are triggered when state of a pin is changed (going 'low' from 'high' state or reverse). Cycles are counted until the interrupt is generated. As interrupt is generated the cycles are compared to the 'default value' (default value is the one taken just after the microcontroller starts its code). If there is a difference - the led is set to high.