ALLPCB
Overview
In recent years, the number of environmentally friendly and battery-powered products has increased, raising demand for low-power human-machine interfaces (HMIs) in applications such as capacitive touch sensors.
Low-Power Measurement and Automatic Judgment
Touch detection requires periodic measurement and judgment, but RX microcontrollers equipped with a CTSU (capacitive touch sensor unit) cannot perform measurement and judgment while in low-power modes, which creates power consumption concerns. The RX140 addresses this with its SNOOZE mode and the CTSU2SL(*) automatic judgment feature, allowing touch measurement and judgment while maintaining low power in SNOOZE mode. CTSU2SL can also be used with MEC (Multiple Electrode Connection) to further reduce power consumption.
MEC Function
MEC treats multiple touch electrodes as a single touch input for measurement. This allows one measurement cycle to cover what previously required several cycles, reducing measurement time and therefore power consumption.
*: CTSU2SL is included on products with 128 KB or more flash. Products with 64 KB flash use CTSU2L, which does not support automatic judgment or MEC.
Application Example
The following shows example applications using the automatic judgment and MEC functions.
In standby, MEC can treat multiple touch buttons as a single start button. The automatic judgment function keeps touch buttons at low power while operating in standby. After wake-up, the buttons function as normal touch inputs.
Evaluation Environment
The evaluation environment used during software development included:
- RX140 capacitive touch evaluation system
- TOUCH middleware / CTSU driver FIT module Rev2.10
- QE for Capacitive Touch V3.1.0 optimization tool
The RX140 capacitive touch evaluation system is a kit for evaluating the functions of touch solutions. FIT and QE were used to develop low-power software for the target application.
