Capacitive Sense
QTouch Library Peripheral Touch Controller: http://ww1.microchip.com/downloads/en/DeviceDoc/atmel-42195-qtouch-library-peripheral-touch-controller_user-guide.pdf
http://ww1.microchip.com/downloads/en/DeviceDoc/qmatrix_white_paper_100.pdf
http://ww1.microchip.com/downloads/en/DeviceDoc/qt60248_402.pdf
Atmel QMatrix
Burst length
number of charge pulses in a burst measurement
Increasing BL increases signal resolution and sensitivity.
Sampling Resistor
discharges Sampling Capacitor(Cs) and controls discharge slope.
Increasing Rsmp increases sensitivity.
X-Y
X transmitter, burst, drive line
Y receiver, sense line
YA port: charge transfer control(top)
YB port: ADC mux input(bottom)
self/mutual capacitance sense
self
mutual
ATMEL QTouch Library
supports GCC tool chain
works with AVR with 2K flash(QTouch only)
QTouch
self
a button per two pins
QMatrix
mutual
http://www.atmel.com/products/TouchSolutions/bsw/qmatrix.aspx
QTouchADC
QTouchADC only requires 1-series resistor and 1-pin per channel. No other external components are required.
QTouchADC offers faster acquisition times with shorter burst lengths, resulting in lower power consumption.
Also can be used promixity sensing.
http://www.atmel.com/products/TouchSolutions/bsw/qtouchadc.aspx
Charge transfer
QTouch Composer
extension for Atmel Studio 6
3.3 Tracking Base Capacitance Value
http://www.ti.com/lit/an/slaa379/slaa379.pdf
TI explains a patent expired method here. (not mutual sensing)
Calibrating
compensate capacitance drift
http://www.embedded.com/design/prototyping-and-development/4008781/Getting-in-touch-with-capacitance-sensor-algorithms
QTouch and QMatrix Sesitivity Tuning: http://www.atmel.com/images/qtan0062.pdf
X-Y electrode design(capacitance)
Bust length
Sampling Capacitor Cs = 4.7-10nF
Sampling Resistor Rsmp = 470K(220K-1M)Ohm
Sensor Design Guide
http://www.atmel.com/images/doc10752.pdf
Promixity sensing
http://www.atmel.com/Images/doc10760.pdf
QTouch 180mm
QTouchADC 250mm
QMatrix 50mm
A QTouch-compatible library for SAMD: https://github.com/adafruit/Adafruit_FreeTouch
Disscussion: https://forums.adafruit.com/viewtopic.php?f=8&p=610501
https://geekhack.org/index.php?topic=76040.0
source code: https://github.com/tmk/capsense_qmatrix
This is resource for analyze Topre capsense method(TP1684).
Waveforms of TP1684 and signal charts of scan switches. http://imgur.com/a/jat2a
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