APPLICATION NOTE
RX113 G roup
Design G uide for Renesas Touch Solution
Summary
The RX113 group has incorporated hardware (Capacitive Touch Sensor Unit; CTSU) that detects human body
contact by measuring capacitance existed between touch electrode and human body.
This app lic a tion note introduces the p rinciple of capacitive touch dete c tion as well as explains the detail of current-
frequency conversion sys tem that is used in RX113.
Target Device
RX113 Group
Contents
Introduction ........................................................................................................................................ 3
The Basic of Capacitive Touch Switch .............................................................................................. 3
Generation of Electrostatic Capacity ................................................................................................................. 4
Capacitance-Current Conversion ...................................................................................................................... 5
Digitizing of Curr e nt ......................................................................................................................................... 7
ON/O F F swit ch judgment ................................................................................................................................. 7
The Capacitive Touch Detection System of Renesas ....................................................................... 9
Overview ........................................................................................................................................................... 9
Hardware ......................................................................................................................................................... 10
Overview ................................................................................................................................................ 10
I/O Driver & Drive pul s e generator ........................................................................................................ 11
Analog Fr ont End ................................................................................................................................... 11
3.2.4 Digital Control & CPU unit .................................................................................................................. 13
Firmware ......................................................................................................................................................... 15
Overview ................................................................................................................................................ 15
3.3.2 Physical Driver ............................................................................................................................................. 15
3.3.3 Middleware .................................................................................................................................................. 15
3.3.4 API ............................................................................................................................................................... 15
3.3.5 Application ................................................................................................................................................ 16
Designing a Touch Board and System............................................................................................ 16
Overview ......................................................................................................................................................... 16
Design of Cap touch board .............................................................................................................................. 16
Design of the self-capacitance method Cap touch key board ................................................................. 16
R01AN2516EU010
Ver. 0.9
Dec. 1, 2014
R01AN2516EU0100 V er . 0.9 Page 1 of 4
Dec. 1, 2014