Capacitive Sense

Atmel QTouch

QTouch Library Peripheral Touch Controller: http://ww1.microchip.com/downloads/en/DeviceDoc/atmel-42195-qtouch-library-peripheral-touch-controller_user-guide.pdf

Arduino Library

A QTouch-compatible library for SAMD: https://github.com/adafruit/Adafruit_FreeTouch

Disscussion: https://forums.adafruit.com/viewtopic.php?f=8&p=610501

Keyboard controller using QMatrix

https://geekhack.org/index.php?topic=76040.0

Resources

mTouch Theory
http://ww1.microchip.com/downloads/en/DeviceDoc/93064A.pdf

Capacitive sensing library for Arduino
http://playground.arduino.cc/Main/CapacitiveSensor?from=Main.CapSense

How Oscilloscope Probes Affect Your Measurement Input capacitance of Probes really affect circuit of capacitive sensor. http://www.tek.com/dl/51W_30013_0_MR_Letter_0.pdf

Analog Devices CapTouch
http://www.analog.com/media/en/technical-documentation/data-sheets/AD7147.pdf

IBM patent: Keyboard multiple switch assembly: http://www.google.co.ug/patents/US4274752

xwhatsit's explanation on IBM method: http://deskthority.net/f-o-r-s-a-l-e-f58/xwhatsit-s-grand-unified-ibm-capsense-usb-controller-thread-t7993-120.html#p165846

Model F keyboards and the 8048 http://www.halicery.com/Hardware/Intel%208042%20and%208048/Notes%20on%20IBM%20Model%20F%20Keyborads.html

xwhatsit's Grand Unified IBM Capsense USB controller thread: https://geekhack.org/index.php?topic=58138.0

Designing a custom Topre board(attheicearcade): http://deskthority.net/workshop-f7/designing-a-custom-topre-board-t11734.html

DPH capsense controller: https://geekhack.org/index.php?topic=52922.0