The TOUCH4 card works with a Baseboard FPGA card to capture touch events on its four input pads.
- Senses touch events on four inputs
- Simple, low cost design
- Uses external pads or pads printed on the card
- Driver automatically adjusts to changes in stray capacitance
- Driver lets you set the sensitivity
The TOUCH4 card and matching FPGA peripheral monitors four pads for touch events. Each touch pad controls the frequency of an RC oscillator. Touching a pad changes the capacitance of the circuit and changes the frequency. The FPGA peripheral accurately measures the four oscillator frequencies and reports them to the pcdaemon host where changes in frequency are reported as touch events.
Solder pads allow the addition of external touch pads.
The schematic and layout of the TOUCH4 are shown below. The Eagle schematic file is available here: touch4.sch and touch4.brd. The bill-of-materials file is available here: touch4.txt.